Final Report Summary - SUSTAFFOR (Bridging effectiveness and sustainability in afforestation / reforestation in a climate change context: new technologies for improving soil features and plant performance)
Executive Summary:
According to FAO (2010), 12 million ha are afforested or reforested yearly worldwide, especially in zones limited by water availability, while in UE27, 100 million trees are planted yearly. The investment on plant establishment is commonly imbalanced with the resources devoted to monitoring and tending operations, resulting in frequent low survival rates, especially in areas suffering from drought. The main causes of failure, besides browsing damage, are drought and competing vegetation. The main current techniques against them imply high economic and environmental costs, with a massive use of fossil fuels, plastics or herbicides.
A group of 6 highly specialized European Small and Medium Enterprises (SMEs – Terrezu, TerraCottem Internacional, La Zeloise, EcoRub, DTC and Ceres) launched a joint project in order to develop new alternatives for increasing the success of tree planting projects, by developing innovative techniques meeting 5 requirements: cost-efficiency, sustained effect, versatility, environmental friendliness and consistent technical features.
This partnership of SMEs launched SUSTAFFOR project (Bridging effectiveness and sustainability in afforestation / reforestation in a climate change context: new technologies for improving soil features and plant performance), for what they contacted 4 Research & Technology Developers in order to evaluate the performance of novel techniques in laboratory and field trials: CTFC, EDMA (ES), CENTEXBEL (BE) and CNRS (FR).
The aim of SUSTAFFOR was to conceive, produce, develop and thoroughly evaluate (at laboratory and field level) novel techniques aiming at improving AF/RF projects from an environmental, technical and economic point of view, and to explore synergies between them. The novel techniques include:
- A new soil conditioner: a mix of products aiming at improving soil conditions, especially water retention capacity where roots grow during the first years, including hydro-absorbent polymers free of polyacrylamide, fertilizer & root growth precursors. This technique aims at mitigating the impact of drought in young plantations, being a one-time alternative to recurrent emergency irrigations.
- Four new groundcovers: these layers are installed in the soil around the tree stem, mitigating the negative effect of competing vegetation and soil water evaporation. The four models include three fully biodegradable versions, based on new biopolymers and on jute fibres treated with organic resin for enhanced durability. The fourth groundcover is a long-lasting (15 years) unit based on recycled rubber. These techniques are an alternative to recurrent and unsustainable weeding options, i.e. herbicide application and mechanical weeding, as well as to plastic mulching.
These techniques were tested in field and laboratory trials in order to ascertain their effect at tree, soil and micro-site level, and compared to reference techniques. Field testing consisted on eight trials distributed across a wide range of conditions (Semiarid, Mediterranean continental, Mediterranean humid, Montane) in NE Spain, representative of most conditions in Europe and the Mediterranean.
The new soil conditioner improved significantly tree performance in areas limited by poor and sandy soils (Semiarid and Montane), especially when limited by water deficit (Semiarid). However, in highly productive sites with rich soils the effect was negligible.
The new groundcovers showed an outstanding performance in terms of tree fitness and soil moisture compared to untreated trees, especially in the most productive sites (Mediterranean continental and humid). The results of these techniques were in general superior to those obtained by herbicide application, and were similar to commercially available plastic groundcovers.
For the moment, there are no major effects detected on the variables related to soil organic matter dynamics.
The new techniques proved to be a feasible alternative (both technically and economically) to current techniques applied against drought and competing vegetation in tree planting, bringing environmental benefits.
Project Context and Objectives:
1. The challenge of tree planting
Tree planting is a major challenge worldwide, mobilizing a vast amount of resources, with a wide range of objectives, often combined in the same space and time:
- productive: forest goods including timber, fruit, fuelwood, game, cork, non-timber forest products, etc.
- protective: especially soil (mitigation of wind and runoff erosion), water (less sediments, higher quality, promotion of infiltration and aquifer recharge) and biodiversity (habitat for flora and wildlife species).
- social: landscape, recreation, prevention of damages on crops or on human health linked to reduced erosion and improved water quality.
According to FAO Global Forest Resources Assessment 2010, an area of 12 million ha is reforested yearly worldwide, a large proportion of which corresponds to zones where primary production is limited by water availability (arid, semiarid and Mediterranean conditions – meaning more than 40% of Earth land surface). In the case of Europe, around 3 million ha of agricultural land only have been afforested in 1990 – 2010, apart from additional several thousand hectares corresponding to ecological restoration of degraded land, artificial regeneration of forests, gardening, landscape plantations (e.g. besides roads or infrastructures), etc. According to UNEP, around 100 million trees are planted yearly in UE27. The global estimation of the area suitable for restoration, where afforestation has a major role, is 2 billion hectares (Laestadius, 2011).
2. Tending operations in tree planting projects
These massive investments for plant establishment are commonly imbalanced with the resources devoted to monitoring and tending operations on the newly planted areas, resulting on frequent partial or total failure of these tree planting projects. The tending operations aim especially at mitigating the negative effect of two factors:
- Drought (especially in areas limited by water availability): the negative effect of drought can be exacerbated by factors including a light soil texture, high temperatures and wind. This event is hardly foreseeable and can occur at any moment and any site. In the framework of climate change, with an expected rise in temperatures and a more uneven distribution of the precipitation, especially in Mediterranean areas, drought events are expected to become increasingly severe.
- Competing vegetation (especially in medium to highly productive sites): because of their fast and vigorous growth, weeds can outcompete newly established trees and shrubs by impeding their access to water, nutrients and light. This unwanted vegetation also hide the planted trees, which pose a difficulty to the maintenance and monitoring activities.
Both negative factors are, besides wildlife damage, the main threats in our conditions, being particularly negative for newly established trees with an underdeveloped root system and thus incapable of reaching a large volume of soil.
The final effect of these two factors, either independently or combined, may range from slight growth reduction, higher sensitivity to pests and diseases, to the mass failure of the tree planting project, leading to major economic losses and social discouragement towards the potential restoration of the area.
3. Traditional versus new approaches of tending operations in tree planting
The traditional approach to tree planting, still applied in most sites in Europe, is to rely on corrective measures against drought and competing vegetation, based on repeated and often unsustainable techniques such as emergency irrigation, herbicide application or mechanical weeding. However, with the increasingly limited resources, the rise of labour costs and equipment and the growing social concern towards sustainability, these practices are more and more inapplicable. If the tree planting project was designed and implemented relaying on the mentioned repeated interventions, and they cannot be ultimately applied, the probability of success of the project is reduced dramatically. For example, Alloza et al (1999) found average success rate of tree planting projects as low as 30%, especially in areas suffering from drought. It is thus necessary to develop new approaches to tree planting, designing the project with the involvement of techniques meeting the following five requirements altogether:
a) Cost-effectiveness: the techniques must be effective against the negative impact of drought and competing vegetation, with a clear increase in tree performance compared to the non-application. This effect must come at the lowest cost possible to be applicable. The cost must refer to the whole cycle of the technique: acquisition, installation / application and disposal.
b) Sustained and cumulative synergic effect on plant fitness (survival and growth) over the first years of plantation, until tree establishment is successful (at least 4-5 years). The use of long-lasting preventive measures is prioritized by most managers of tree planting projects, as allowing a better planning of the investment.
c) Versatility: the technique must be valid in a wide range of climatic and soil conditions and for multiple purposes: any activity implying tree or shrub plantation, both individually and combined with other techniques.
d) Environmental friendliness: the social concern and the level of environmental impact of human activities are resulting in a legal framework more and more restrictive with regard to the techniques and materials that can be utilized. Thus, there is a growing need for sustainable techniques, considering the whole lifetime: raw materials, production, application/utilization and disposal. Some social and environmental requirements of growing importance are: avoidance of toxicity for soil, water and air, low visual impact, use of locally produced materials for reducing low carbon footprint, etc.
e) Well-known technical features: a commercial product should have well-known and features regarding composition, durability and degradability, as well as foreseeable performance, in order to ease its labeling and use prescription
4. Most common techniques applied to mitigate drought impact on tree planting projects
The main techniques aiming at reducing the negative impact of drought in tree planting projects in Europe are two:
- Special soil preparation, including water harvesting and micro-catchments. This technique pretends to modify micro-physiography to concentrate runoff, and/or to perform a deep soil preparation (up to 80 cm depth). This is a preventive measure with very variable level of cost and environmental impact depending on the particular technique an area.
- Artificial water application: depending on the context of the tree planting project (especially, the accessibility of the site) water can be applied with pre-installed drippers (easily accessible sites) or with water wagons. In both cases, the techniques imply high application costs, a massive investment of labour and a noticeable environmental impact.
As an alternative or complement to both types of techniques, the last years have witnessed the development of soil conditioners. This product is mixed with the soil at the planting pit to improve the physical (and often chemical) features at micro-site level, especially, water holding capacity. Apart from organic conditioners (peat, biochar, sawdust) and mineral conditioners (perlite, vermiculite, sand / clay, etc), synthetic options are being more and more utilized by managers. Synthetic soil conditioners include in its composition hydro-absorbent polymers, which are able to store large amounts of water keeping it available for the tree roots and reducing the losses from evaporation and percolation. The main advantages of soil conditioners in general, and synthetic ones in particular, include its simple application (one-time only, during tree planting), versatility and low dosage required. However, the synthetic versions have a drawback, which is the poor social perception of some of the polymers utilized, especially, polyacrylamide.
5. Most common techniques applied to mitigate competing vegetation impact on tree planting projects
The main techniques applied to control competing vegetation in tree planting projects are:
- Mechanical weeding: consisting on destroying competing vegetation with man-operated tools or machines (e.g. brush cutter) or with tractor-operated devices (plough, flail mower). Both cases involve the use of fossil fuels and the risk of damaging the trees (if applied close to the stem) or being ineffective (if applied far from the stem).
- Chemical weeding: application of herbicides to prevent the germination or to suppress competing vegetation. Because of the environmental damages, this technique is strongly regulated with regard to the products and doses that are applicable. Moreover, this practice raises a growing social concern, and its use is being progressively restricted in protected areas and public forests in many countries.
Apart from the mentioned limitations of these techniques, both options imply repeated applications, which are more frequent as the site is more productive. As a result of these limitations, in the last years a technique developed in agriculture is being progressively introduced to tree planting projects: the use of groundcovers. This technique consists on covering the soil besides a tree (or along a row of trees), for impeding the establishment or proliferation of competing vegetation near the stem. The groundcover (also known as “mulch”) has a triple effect: avoids the germination and install of competing vegetation, mitigates soil water evaporation and eases the finding of young seedlings for maintenance and monitoring purposes. There is a wide range of products that can be utilized for this purpose: organic waste or by-products from agricultural or forest operations (straw, chips, bark), stones and layers made of plastic, paper, textiles, cardboard or long-lasting materials. For the moment, the most common material is a thin plastic layer, because of its low retail price, but it has as main drawback the need to remove it from each tree at the end of its service life (5-6 years), which is an expensive intervention. As a result, in the last years new materials are being developed, especially, biodegradable options which allow avoiding the need for removing the groundcover, as well as long-lasting groundcovers which can be utilized in long-term tree planting purposes (e.g. gardening) or reutilized several times.
6. SMEs and RTDs partnerships: collaborating for developing improved solutions for tree planting
The state of the art described makes evident that there is a need for having innovative solutions for avoiding the negative effects of drought and competing vegetation with techniques that meet the five requirements described in the point 3. In this sense, both soil conditioners and biodegradable / long lasting groundcovers seem to be interesting lines to explore, both individually and combined: as the soil conditioners improve site features at micro-site level, it is expected that competing vegetation might also favour from this enhancement. Therefore, the combination of new generation synthetic soil conditioners and groundcovers may lead to a synergic manner to mitigate the negative effect of both drought and competing vegetation. This is the leading principle and the origin of Sustaffor project.
A group of specialized SMEs producing soil conditioners (Terracottem Internacional) and materials which can be utilised for groundcover fabrication (DTC, La Zeloise and EcoRub) were put in contact by two SMEs specialized in eco-innovative solutions for environmental engineering, forest restoration and landcaping: Terrezu and Ceres. This partnership launched SUSTAFFOR project (Bridging effectiveness and sustainability in afforestation / reforestation in a climate change context: new technologies for improving soil features and plant performance). In order to multiply the impact and interest of the new techniques to develop, they contacted several Research and Technology Developers (RTDs), with different functions:
- Forest Sciences Centre of Catalonia, to provide support in aspects such as technical requirements of the new techniques and the assessment of their performance in field conditions, considering a wide range of tree, soil and environmental parameters.
- Edma Innova, to support the settlement of monitoring equipment in the field trials
- CNRS- IC2MP - Environmental and Material Chemistry Institute of Poitiers, to provide a cutting-edge technology and analytic capacity to characterize the effects of the degradation of the innovative techniques in the soil.
- Centexbel, to provide know-how related to the fabrication routes of the groundcovers and to perform degradation tests.
This collaboration of SMEs and RTDs has resulted in the achievement and assessment of novel techniques, tested and characterized in detail, both individually and combined, and compared to reference techniques. The innovative techniques developed during the project are five:
- An innovative soil conditioner, including a new high-performance hydro-absorbent polymer free of acrylamide in an improved mixture of 20+ ingredients (TerraCottem Internacional).
- A 100% biodegradable framed groundcover made of a new biopolymer formulation, fused to a flexible bioplastic sheet (DTC).
- A 100% biodegradable semi-rigid groundcover, made of a new biopolymer formulation (DTC).
- A 100% biodegradable goundcover made of woven jute fibres treated with furan bio-based resin for increased durability (La Zeloise).
- A long-lasting (10-15 years) groundcover based on recycled rubber and anti-UV treated for enhanced durability (EcoRub).
6. Objectives of Sustaffor project
The main objective of SUSTAFFOR is to conceive, produce, develop and on-field validate novel techniques aiming at improving afforestation / reforestation projects from an environmental, technical and economic point of view, as well as to explore the synergies between them.
Moreover there are thematic objectives, described below:
Technical-scientific objectives
- To improve tree water status and soil water retention thanks to the soil conditioner
- To increase the durability and estimate the service life of novel mulching techniques
- To reduce overall service costs of weeding techniques
- To increase and quantify the positive effects on tree fitness, and the synergic effect of combining mulching and soil conditioning techniques
- To improve and quantify the positive effect of novel techniques on key soil physical and chemical features
- To reduce global AF/RF costs during the first 5 years
Commercial objectives
- Strengthen the market position of the participating SMEs
- Exploitation Intellectual Property Rights (IPR) of the novel techniques
- Raise awareness of managers and end-users on the technical and environmental benefits of soil conditioners and biodegradable or multiple-use mulching
Environmental-social objectives
- To use acrylamide-free polymers in soil conditioners
- To reduce the use of plastics, herbicides, water and fossil fuels consumption in the establishment and maintenance of AF/RF projects
Project Results:
The vast quantity of variables gathered and results obtained during the project makes necessary to organize them in a consistent manner. They will be presented below, organized as follows:
1. Description of the experimental design, field trials and variables monitored.
2. Main results for each variable.
3. Main results and conclusions for the different novel techniques developed in the project.
The results are described in general terms, and more detailed information can be found in the attached information and in the publications prepared during the project.
1. Novel techniques, experimental design and variables monitoring
This section describes the novel techniques developed during the project, the treatments considered, the experimental design of the field and laboratory trials and the whole set of variables studied.
1.1. Development and description of the innovative techniques
1.1.1. Novel acrylamide-free soil conditioner (TerraCottem Internacional)
Although it has been proven that the Terracottem soil-conditioner TCU® enhances drastically the growth of plants and has no negative ecological effects, there is still a concern in the market, since the material is partially based on polyacrylamide chemistry.
An intensive reformulation program was started to develop and alternative polyacrylamide-free soil conditioner that still retains or further improves the properties of the reference Terracottem TCU. After primary chemical analysis a dozen formulations were tested in fast bio-screening trials in green-houses to assess the performance as soil-conditioner.
Based on these results a final optimised formulation encoded TCUplus was selected for upscaling trials and supplied for the further afforestation field trials. This final product was produced in appropriate amounts for the planned Sustaffor field trials and after quality controls sent to the coordinator CTFC.
1.1.2. Novel full-plate biodegradable groundcover via injection moulding (DTC)
For the development of novel groundcover system a first route followed is by injection moulding technology. Instead of using petrochemical based polymers such as PP or PE, biopolymers were used. Several polymer types including PLA, PHA, starch-based and blends of them were evaluated, both for processability properties and intrinsic properties of the injection moulded parts including, flexibility, strength and impact resistance.
Finally a special designed biopolymer blend was defined for the final production trials offering the best performance both in processability and in properties.
A special mould was designed in order to produce in a single step a groundcover of 40 by 40 cm, specially adapted to facilitate installation. It was also possible to combine 4 groundcovers to create larger model of 80 by 80 cm.
1.1.3. Novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (DTC)
A support structure made of biopolymers was injection moulded directly on a biodegradable biopolymer film. Although the film part may have a lower durability than the injection moulded part, the advantages are that a lightweight and economic structure is obtained, that still can easily be installed and fixed to the ground due to the semi-rigid rim.
1.1.4. Novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (La Zeloise).
Groundcovers made of jute fibres are commercially available and can already be used as groundcover. However their durability especially in warm and humid environment is limited. As a result, La Zeloise has used a novel approach by applying a bioresin that acts as a preservative and extends the lifetime of the product. The bioresin formulation along with the application process required further optimisation to get optimal performance of the groundcover. Also the impact on mechanical properties and stiffness was examined and brought under control by selection of formulation, process methodology and applied concentration. Due to the raised stiffness of the fabric, the groundcovers are easier to handle during installation around the tree. The materials are not only fully biobased but offer as well a full biodegradability after an extended lifetime of about 3 to 5 years. The bioresin treated fabric show also improved properties against flammability.
Since production is performed in full width via roll to roll impregnation, drying, curing groundcovers can be produced in a flexible way in all varieties of sizes.
1.1.5. Novel long-lasting groundcover made of recycled rubber (EcoRub)
The use of recycled materials to build groundcovers can offer large ecological benefits. Ecorub produces a range of different articles based recycled rubber offering a second life to materials that normally will be burned or deposited.
Based on their technology, a rubber mat was created to be used as groundcover. The material is not biodegradable but instead it can be used for a long time (10-15 years). For the Sustaffor project a thickness of 1.5 mm was selected offering an appropriate balance in strength, weight, handling and installation possibilities, as avoiding the need for being removed at the end of its service life.
1.2. Techniques tested and experimental design.
The performance of these novel soil conditioners and groundcovers were tested in a range of eight outdoor field trials. In order to assess their performance, they were compared to reference techniques, i.e. those currently applied for the same purpose. Moreover, the different types of techniques were combined to conform a range of experimental treatments.
1.2.1. Techniques aiming at minimizing drought negative impact
The techniques aiming at minimizing drought negative impact on tree planting were, for seven of the field trials:
- The described novel soil conditioner (1.1.1) at the prescribed dose (40 g/tree). This technique is coded “TCU+40g” hereinafter.
- The described novel soil conditioner (1.1.1) at a lower dose (20 g/tree), coded “TCU+20g” hereinafter.
- The described novel soil conditioner (1.1.1) at a higher dose (80 g/tree), coded “TCU+80g” hereinafter.
- A reference commercial soil conditioner TerraCottem Universal at the prescribed dose (40 g/tree), coded “TCUStd40g” hereinafter.
- Control (no application of soil conditioner), coded “NoSC” hereinafter.
In the remaining field trial (numbered 4) involving trees mycorrhized with edible fungi, a different group of techniques were applied to mitigate drought negative effects:
- The described novel soil conditioner (1.1.1) at the prescribed dose (40 g/tree).
- A reference commercial soil conditioner consisting only on hydrogel (hydroabsorbent polymer alone) at a dose of 50 g/tree, coded “CommHydrogel” hereinafter.
- A reference commercial organic soil conditioner consisting on peat, at a dose of 360 g/tree, coded “CommPeat” hereinafter.
- Control (no application of soil conditioner).
1.2.2. Techniques aiming at minimizing competing vegetation negative impact
The techniques chosen were, for seven of the field trials, the following:
- The described novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (1.1.3) coded “BIOPOLYMER” hereinafter.
- The described novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (1.1.4) coded “JUTE” hereinafter.
- The described novel long-lasting groundcover made of recycled rubber (1.1.5) coded “RUBBER” hereinafter.
- A reference commercial biodegradable woven film, coded “CommBiofilm” hereinafter.
- A reference commercial plastic (polyethylene) film, treated anti-UV, coded “CommPE” hereinafter.
- A reference commercial herbicide (glyphosate) application, every spring, coded “CommHerbicide” hereinafter.
- Control (no application of any technique against competing vegetation), coded “NoWeeding” hereinafter.
Moreover, in two of the field trials (numbered 7 and 8), the described novel full-plate biodegradable groundcover via injection moulding (1.1.2) was also tested, coded FULLPLATE. The limitations in the production process made that no further units were available for the rest of the field trials.
In the remaining field trial, numbered 4, the assessed techniques aiming at controlling competing vegetation were the following:
- The described novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (1.1.3).
- The described novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (1.1.4).
- The described novel long-lasting groundcover made of recycled rubber (1.1.5).
- A reference commercial plastic (polypropylene) woven mat, treated anti-UV, coded “CommPP” hereinafter.
- A reference commercial herbicide (glyphosate) application, every spring.
- A reference mechanical weeding (hoe) application, every spring, coded “CommMechanical” hereinafter.
- Control (no application of any technique against competing vegetation).
1.2.3. Experimental treatments
The experimental treatments are combinations of the different techniques utilized to control the negative impact of drought and of competing vegetation. The combinations are the following (see codes above):
For seven of the field trials:
- All the techniques applied to mitigate drought effects combined with CommPE
- All the techniques applied to control competing vegetation combined with TCU+40
- All the techniques applied to control competing vegetation combined with NoSC
In total, 17 treatments (19 in the case of field trials 7 and 8) were installed in each field trial. Each of these treatments was applied to 30 trees, distributed following a full random block design, with 6 blocks per field trial composed of 5 trees from each treatment.
In the case of field trial 4, the treatments were:
- All the techniques applied to mitigate drought effects combined with CommPP
- All the techniques applied to mitigate drought effects combined with NoWeeding
- All the techniques against competing vegetation combined with TCU+40
In total, 13 treatments were installed at 12 trees each. The treatments were organized following a full random block design, with 12 blocks composed of 1 tree from each treatment.
The total number of experimental trees was 3,846.
1.3. Field trials
The eight field trials were deployed in four strongly contrasting conditions located in northeast Spain, representative of most conditions in Europe and the Mediterranean:
1.3.1. Semiarid bioclimate with light soil (Field trials 1 and 2): located in Mequinenza municipality (Saragossa province), in conditions severely limited by water availability linked with poor precipitation regime (370 mm annual precipitation, 70 of which during summer), high temperatures (15ºC mean annual temperature, 30ºC mean temperature of the warmest month), a light soil (loamy-sandy texture) a steep slope (40-70%) and, in the case of field trial number 1, a south-facing aspect. These field trials, located in a forest area burnt in 2005, were planted with Aleppo pine (Pinus halepensis). Because of the poor productivity of the site, the techniques applied to control competing vegetation were 40x40 cm, and it was not necessary to apply the treatment CommHerbicide.
1.3.2. Mediterranean continental bioclimate with rich soil (Field trials 3 and 4): located in Solsona municipality (Lleida province), in conditions limited by slight to moderate summer drought. The site is very productive, located in two flat former agricultural fields on fertile soils, rich and with moderately heavy texture (loamy-clayish). Mean annual precipitation is 685 mm (185 of which during summer) and mean annual temperature is mild (12 ºC). These trials were planted with hybrid walnut (Juglans x intermedia) and holm oak (Quercus ilex) mycorrhized with black truffle (Tuber melanosporum). The techniques applied to control competing vegetation were 80x80 cm.
1.3.3. Mediterranean humid bioclimate with rich soil (Field trials 5 and 6): located in Banyoles municipality (Girona province), in very productive conditions slightly limited by punctual summer drought events. The field trials are located in two flat former agricultural fields on fertile soils, rich and with moderately heavy texture (loamy-silty). Mean annual precipitation is 870 mm (215 of which during summer) and mean annual temperature is warm (14 ºC). These trials were planted with hybrid walnut (Juglans x intermedia) and stone pine (Pinus pinea). The techniques applied to control competing vegetation were 80x80 cm.
1.3.4. Montane bioclimate with poor, light soil (Field trials 7 and 8): located in Fontanals de Cerdanya municipality (Girona province), in conditions limited by a light textured soil (loamy-sandy), low temperatures (7.5ºC mean annual temperature, 0ºC mean temperature of coldest month) and north aspect, and by a moderate slope (30% in average). Mean annual precipitation is 885 mm (270 of which during summer). These trials were planted with European ash (Fraxinus excelsior) and birch (Betula pendula). Because of the poor productivity of the site, the techniques applied to control competing vegetation were 40x40 cm, and it was not necessary to apply the treatment CommHerbicide.
1.4. Monitoring
The following variables have been monitored between April 2014 and October 2015, totalling 2 vegetative periods:
1.4.1. Tree related variables: the variables most related to tree performance were monitored:
1.4.1.a Survival and vegetative status: assessed by direct observation at the end of each vegetative period, for all trees.
1.4.1.b Tree aerial growth: basal diameter and height measured with digital calliper and measuring tape, respectively, at the moment of planting and at the end of each vegetative period, for all trees. Tree volume is calculated as a cone with the tree basal area and the height of the tree. Tree growth of a given year is obtained as the difference between the initial and the final volume.
1.4.1.c Tree biomass allocation: six trees per treatment were pulled up at the end of the first vegetative period for calculating the dry biomass of different tree organs: fine roots (< 2mm diameter), coarse roots (> 2mm diameter), stem, needles (in the case of pine). This work was done in field trials 1, 2 and 3.
1.4.1.d Tree water status: six randomly selected trees per treatment were monitored four times during summers of 2014 and 2015 for determining the level of water-related stress. The methods applied were Relative Water Content in the case of pine (percentage of water present on the needles with respect to saturated content) and leaf water potential (strength with which the tree retains the water in the leaf tissues), measured for broadleaved species with Schölander chamber). These variables were measured in field trials 1, 2, 3, 5 and 7.
1.4.1.e Tree nutrient status: six randomly selected trees per treatment were monitored two times during summers of 2014 and 2015 for assessing their nutrient status. The method utilized was a SPAD-meter, a proxy of the chlorophyll content, and thus an indication of the nitrogen availability in the trees. This variable was measured in field trials 3, 4, 5 and 7.
1.4.2. (Micro-)environmental variables: the most relevant variables occurring at (micro-)site level affecting tree performance have been assessed.
1.4.2.a Soil moisture: measured in three trees per treatment in each field trial, seven times per year, between spring and autumn, at two different depths: 0-20 cm i 20-40 cm. The method has been a TDR probe inserted in pre-installed tecanate tubes. This variable was measured in field trials 1, 2, 3, 4, 5 and 7.
1.4.2.b Soil temperature: measured in a continuous basis in three trees per weeding treatment, through thermometers with built-in dataloggers, installed at two different depths: 5 cm and 15 cm. This variable was measured in field trials 1, 2, 3, 4, 5 and 7.
1.4.2.c Weather: a network of meteorological stations were installed in field trials 1, 2, 3, 5 and 7. These stations made a continuous recording of the most important weather variables: temperature, air humidity, precipitation, wind speed and direction, total radiation and UV radiation.
1.5. Soil variables
The most relevant variables related to soil organic matter dynamics were monitored in order to determine how they were affected by the different experimental treatments.
Although it was initially foreseen to analyse also total nitrogen, extractable ammonium, extractable nitrate and extractable phosphorus it was finally discarded in light of poor expectations of detecting relevant changes. Instead the study focused on:
1.5.1. Soil organic carbon: it was measured as an indicator of soil microbial activity. As a result of the (expected) increase in soil water retention and probably also changes in soil thermal regime due to the application of soil conditioners and/or groundcovers, we may expect an increase in soil microbial activity. This should result in an acceleration of soil organic matter decomposition, owing to the saprophyte regime of most soil biota. We looked for differences in soil organic carbon associated to either the presence of soil conditioner or the different groundcovers; a consistently lower value obtained for controls would mean that decomposition is enhanced. Organic carbon was analysed by dichromate oxidation, following the modified Mebius’ method (Nelson & Sommers, 1996).
1.5.2. Biochemical fractionation of soil organic matter: the aim was to detect changes in the structure of the soil organic matter stock. Since the decomposability of soil organic matter is the result of such a structure, these changes should precede the decomposition itself. The acid hydrolysis procedure of Rovira et al. (2012) was applied. By this method soil organic matter in ground soil samples is submitted to three consecutive extractions: (i) with hot K2SO4 0.5 M solution (water-soluble fraction, WS); (ii) with hot 2.5 M H2SO4 (labile pool 1, LP 1); and (iii) with cold 13M H2SO4, then diluted to 1M and boiled for 3 h (labile pool 2, LP 2). The unhydrolyzed residue is taken as the recalcitrant fraction. The liquid extracts and hydrolysates were analyzed for carbohydrates and phenolics.
The method is based upon standard methods to quantify polysaccharides in plants. The second hydrolysate (LP 2) matches the operational definition of cellulose, and therefore the ratio LP2 / total equals to the cellulose to total carbohydrates ratio. It has been shown that in soil samples this ratio decreases with decomposition. High values for this ratio may be interpreted as signs of abundance of fresh plant-derived materials.
1.5.3. Detection of specific organic compounds in the soil organic matter, as indicators of the degree of microbial reworking, and therefore of an accelerated or retarded biochemical evolution. Soil samples were subject to thermochemolysis with TMAH (tetramethylammonium hydroxide) in the presence of methanol, under N2 atmosphere at 450ºC. This treatment breaks polymers onto their monomeric composers, which are methylated and removed by a N2 stream. The released compounds are collected in cold (0 ºC) trichloromethane, concentrated and transferred to a vial, dried and redissolved in dichloromethane, then injected into a Hewlett-Packard gas chromatograph-mass spectrometer system. Identification of compounds was done from the mass spectra by comparison with published spectra and own data.
Data analysis focused on the detection and quantification of several groups of substances: fatty acids, sugars, and phenolics. For all these substances, there are several indices useful for evaluating the degree of microbial reworking and biochemical evolution.
The sampling was performed in field trials 1, 2, 3, 5 and 7, organized in three campaigns: March 2014, prior to planting (initial soil features, Sampling 0), October 2014 (after 6 months, Sampling 1) and June 2015 (after 14 months, Sampling 2). In each campaign, six samples were collected from each treatment and field trial, at two different soil depths: 0-10 cm and 10-20 cm. These six samples were finally grouped in three composite samples, each made by pooling two of them, chosen randomly. In total there are three composite samples per treatment and depth.
1.4. Groundcover durability / degradability study
Standardised mechanical tests are performed for the different groundcovers, to characterize their properties and how they are modified over time: tenacity, modulus at break and elongation. They are measured on a drawbench on a strip of woven textile, foil or plastic or rubber plate, according the respective standards: ISO 527 for the rubber and plastic plates (standard punched tensile bars; width 10 mm), ISO 13934 for the textiles and foils (test specimen width 25 mm).
These tests were applied to groundcover samples subjected to both artificial and real weathering:
- Artificial weathering: samples were put in Q-UV test chambers according to the standard ISO 4892-3. Materials were subjected to UV-A and/or UV-B illumination, according to the expected durability performance. Rubber or thick plastic plates are usually tested using the more aggressive UV-B light, in order to reduce treatment time to observe some degradation effects.
- Weathering in field conditions: ten samples from each groundcover were installed in April 2014 in areas annex to the field trials 1, 5 and 7. About 6, 12 and 18 months after installation samples were retrieved from the testing fields and the mentioned mechanical properties were analysed to evaluate the degradation.
2. Main results related to tree performance variables
2.1. Tree survival and vegetative status, at the end of 2015 vegetative period:
2.1.1. Field trial 1: 77% alive & healthy, 2% alive with vegetative problems; 21% dead
The trees with soil conditioner resulted in higher survival rates (77%) than those without it (63%). The survival rate was increased with soil conditioner dosage 71% for TCU+20g, 75% for TCU+40g and 79% for TCU+80g.
Likewise, those with any technique to control competing vegetation showed higher survival rates (80% in average) than those without (66%). JUTE and RUBBER groundcovers achieved the highest survival rates (86% and 87%, respectively), while CommPE led to poorest survival (70%) among the different groundcovers.
2.1.2. Field trial 2: 87% alive & healthy, 0% alive with vegetative problems; 12% dead
The use of soil conditioner led to higher survival rates (92%) than in the case of not using this technique (85%). There was not a clear trend in survival rates depending on the dosage.
However, trees with any technique to control competing vegetation showed slightly lower survival rates (84% in average) than those without them (92%). BIOPOLYMER groundcover led to highest survival rate (90%) among the different groundcovers, while RUBBER (77%) was the only one with survival rates below 80%.
2.1.3. Field trial 3: 87% alive & healthy, 9% alive with vegetative problems; 4% dead
There were no major effects of the application of soil conditioner or of techniques aiming at mitigating the negative effects of competing vegetation.
2.1.4. Field trial 4: 86% alive & healthy, 9% alive with vegetative problems; 6% dead
The use of soil conditioners slightly increased survival rates (95%) compared to NoSC (92%). The different soil conditioning treatments had very different results between them: CommHydrogel led to survival rates of 86%, while both TCU+40g and CommPeat resulted in 96% survival rates.
The use of techniques to control competing vegetation was positive to survival rate, compared to not using them (98% vs 88%). Among them, CommMechanical provided the poorest results (88% survival), while all the others avoided mortality.
2.1.5. Field trial 5: 92% alive & healthy, 8% alive with vegetative problems; 0% dead
The lack of mortality in these field trials makes impossible to compare among treatments.
2.1.6. Field trial 6: 89% alive & healthy, 5% alive with vegetative problems; 7% dead
Soil conditioners did not affect survival rates in this field trial. Similarly, the use of techniques against competing vegetation did not have a decisive impact on survival rates compared to untreated trees. However, the different techniques led to contrasting results: BIOPOLYMER groundcover resulted in full survival (100%), while CommHerbicide and CommBiofilm led to poorest survival results (90% and 83%, respectively).
2.1.7. Field trial 7: 23% alive & healthy, 71% alive with vegetative problems; 7% dead
Most of vegetative problems were caused by the wildlife, despite the perimetric fence installed in the site. The survival rate is very high in any case, averaging 93%.
The use of soil conditioner was positive to survival rate, which was increased from 90% to 95% with the use of this technique. The effect of the different doses were not remarkable.
There was no effect of applying techniques to control competing vegetation on the survival rates, either compared with untreated trees or compared among them.
2.1.8. Field trial 8: 72% alive & healthy, 20% alive with vegetative problems; 8% dead
Like in the case of field trial 7, approximately the half of vegetative problems were caused by wildlife damages.
The use of soil conditioner increased survival rate from 91% (NoSC) to 96%. There was a positive effect with increased dose: survival rates were 90, 97% and 100% for doses of 20, 40 and 80 g/tree, respectively.
Finally, the use of techniques to mitigate competing vegetation impact did not have a major effect on tree survival. However, the different weeding techniques led to different survival rates, with RUBBER, BIOPOLYMER and FULLPLATE leading to highest values (97%, 95% and 94%, respectively) and CommPE, CommBiofilm and JUTE leading to lowest survival rates (88%, 88% and 90%, respectively.
2.2. Tree aerial growth
As the dataset is large and complex to describe as text, we will provide, for each field trial, the significant differences between treatments with regard to tree aerial volume growth. With that aim, we will show the grouping of treatments according to the Duncan test. Different letters (a, b, c) indicate that the treatments are significantly different (p<0.05) being “a” the treatment with the lowest value of growth and “b”, “c”, etc, higher values of growth.
2.2.1. Field trial 1:
The soil conditioner increased tree growth compared to NoSC in both 2014 and 2015, with higher growth rates as the dose is increased: NoSC (“a” in 2014, “a” in 2015); TCUStd40g and TCU+20 g (b, ab) and finally TCU+40g and TCU+80 g (b, b).
Similarly, treatments to control competing vegetation in general also increased tree growth: NoWeeding (a, a) in front of CommPE (ab, b), JUTE (b, ab) and BIOPOLYMER (b, b).
2.2.2. Field trial 2:
The positive effect of soil conditioner on tree growth was noticeable and consistent, with all formulations and doses providing significantly higher rates than NoSC in both 2014 and 2015. There were no significant differences between the different products and doses.
In the case of the treatments to control competing vegetation, the gain in tree growth was less remarkable, although present for most techniques: NoWeeding (a, ab) led to the worst results, not improved by BIOPOLYMER (abc, a), CommPE (abc, bc) or RUBBER (ab, bc). However, CommBiofilm (bc, bc) and especially JUTE (c, c) did improved notable the results of NoWeeding.
2.2.3. Field trial 3:
The soil conditioner did not have a significant effect of tree growth at this field trial.
However, the techniques to control competing vegetation had a remarkably positive effect: all the techniques had superior aerial growth results than NoWeeding in both 2014 and 2015, with the only exception of CommBiofilm in 2015, which led not statistically higher growth rate than Noweeding.
2.2.4. Field trial 4:
The soil conditioner did not have a significant effect of tree growth at this field trial.
Some of the techniques to control competing vegetation improved the results of NoWeeding (a, a): CommPP in 2015 (ab, b), BIOPOLYMER in 2014 (b, ab) and RUBBER both years (b, b).
2.2.5. Field trial 5:
The soil conditioner did not have a significant effect of tree growth at this field trial. However, the techniques aimed at controlling competing vegetation had a remarkable effect: all of them increased tree growth both years (b, b) compared to NoWeeding (a, a), with the only exception of CommBiofilm in 2015 (b, ab).
2.2.6. Field trial 6:
Like in the previous field trial, the soil conditioner did not have a significant effect of tree growth, while the techniques to control competing vegetation led in general to results superior to NoWeeding (a, a), and with noticeable differences between them: CommHerbicide (ab, bc), CommBiofilm (bc, ab), BIOPOLYMER and RUBBER (c, bcd), JUTE (c, cd) and CommPE (c, d).
2.2.7. Field trial 7:
The soil conditioner significantly increased tree growth in 2014, but not in 2015. The growth of trees with NoSC (a) was not significantly worse than TCU+20g (ab), but the other doses and formulations showed better results: TCUstd40g (bc) and TCU+40g and TCU+80g (c).
On the contrary, the different treatments to control competing vegetation did not have an influence on tree aerial growth.
2.2.8. Field trial 8:
Soil conditioning did not have an effect on tree aerial growth, unlike some techniques against competing vegetation: NoWeeding (ab, a) resulted in lower tree growth rates than CommPE (c, b) and than BIOPOLYMER in 2014 (c, ab).
2.3. Tree biomass allocation
Like in the case of tree aerial growth, only the significant differences between treatments will be shown. As mentioned before, this variable was only measured in field trials 1, 2 and 3.
2.3.1. Field trial 1
Root biomass and Total biomass were increased thank to the soil conditioner when applied in doses of 40 g/tree (in both formulations) and 80 g/tree. The lower dose (20 g/tree) did not lead to significantly higher root biomass (ab) than NoSC (a), in both variables.
In the case of the techniques to control competing vegetation, BIOPOLYMER also led to higher root biomass than NoSC.
2.3.2. Field trial 2
Neither the soil conditioners nor the techniques to control competing vegetation had a decisive effect on biomass allocation in this field trial.
2.3.3. Field trial 3
The soil conditioner did not have an influence on biomass allocation. However, the use of techniques to control competing vegetation led to gains in fine, coarse and total root biomass, as well as in aerial and total tree biomass. Compared to NoWeeding, JUTE, BIOPOLYMER and RUBBER increased the results of all the mentioned components, without major differences between these treatments. These treatments also provided higher results than CommHerbi for fine, coarse and total root biomass and for total tree biomass, and than CommPE for fine and total root biomass. CommBiofilm increased coarse and total root biomass, as well as total tree biomass, compared to NoWeeding.
2.4. Tree water status
As mentioned above, this variable was measured in field trials 1, 2, 3, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment.
In the field trial 1, all types and dosages of soil conditioner led to significantly higher needle relative water content than NoSC, although no remarkable differences were found between the different soil conditioner applications. The different techniques against to control competing vegetation did not have a decisive effect on tree water status.
In the field trial 3, both JUTE and CommBiofilm (c) increased the results of tree water status compared to CommHerbicide and CommPE (a) and to NoWeeding and BIOPOLYMER (ab).
In the other field trials where tree water status was monitored the different treatments did not have a decisive influence.
2.5. Tree nutrient status
As mentioned above, this variable was measured in field trials 1, 2, 3, 4, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment. The significant differences found between treatments did not follow a consistent trend in any of the field trials.
3. Main results related to (micro-)environmental variables
3.1. Soil moisture
As mentioned above, this variable was measured in field trials 1, 2, 3, 4, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment.
The only case where significant differences between treatments were found were:
- Field trial 1, 0-20 cm depth: BIOPOLYMER (bc), JUTE and RUBBER (c) increased soil moisture at this depth, compared to NoWeeding (a). CommPE (abc) and CommBiofim (ab) led to intermediate results. Likewise, in 20-40 cm depth, CommPlastic (b) led to higher soil moisture than NoWeeding, CommBiofilm, BIOPOLYMER and JUTE (a).
- Field trial 2, 20-40 cm depth: all the techniques to control competing vegetation increased soil moisture compared to NoWeeding (a). CommPE and RUBBER (c) led to higher soil moisture at this depth than CommBiofilm, BIOPOLYMER and JUTE (b).
- Field trial 5, 20-40 cm depth: BIOPOLYMER (b) resulted in higher soil moisture than NoWeeding, RUBBER and JUTE (a).
- Field trial 7, 0-20 cm depth and 20-40 cm depth: BIOPOLYMER resulted, in both cases, to higher soil moisture than CommBiofilm.
4. Main results related to soils features
4.1. Soil organic carbon
The average values for total organic carbon in the different field trials ranged from 1.02 to 2.07%. Values were usually slightly lower as depth increased. Even when in some cases (Field trial 7) the values of sampling 2 were consistently lower than in sampling 1, usually differences between the two samplings were too small and not statistically significant. Thus it is not possible to state a true decrease in organic carbon content, and therefore we cannot reliably quantify soil organic matter decomposition.
The soil conditioner did not have a significant effect on soil organic carbon content in any of the samplings or field trials.
In the case of techniques applied to control competing vegetation, few differences were found: Field trial 1, sampling 2, all depths; Field trial 3, sampling 2, 10-20 cm depth and Field trial 5, sampling 2, 0-10 cm depth. Often, the organic carbon content was lowest under JUTE. These effects, however, were not consistent enough to state that a given type of mulch results in the highest enhancement of microbial activity.
Table 1. Organic carbon content (% w/w). Average values for different sites, at two depths, and two samplings. The asterisk (*) indicates that significant differences were found linked to the technique for controlling competing vegetation.
0-10 cm depth 10-20 cm depth
Field trial Sampling 1 Sampling 2 Sampling 1 Sampling 2
Field trial 1 1.16 ± 0.34 1.02 ± 0.33 * 0.94 ± 0.35 0.95 ± 0.33 *
Field trial 2 1.50 ± 0.51 1.38 ± 0.38 1.45 ± 0.49 * 1.27 ± 0.45
Field trial 3 1.49 ± 0.13 1.62 ± 0.13 1.16 ± 0.10 1.42 ± 0.13 *
Field trial 5 1.51 ± 0.11 1.46 ± 0.18 * 1.23 ± 0.09 1.31 ± 0.20
Field trial 7 1.89 ± 0.56 2.07 ± 0.68 1.42 ± 0.62 1.78 ± 0.60
Since the pits were maintained mostly free of any input of organic matter, we expected a decrease in SOM, because SOM decomposition was the main (not to say the unique) process occurring in the plantation pits. The fact that no consistent decrease between samplings 1 and 2 was detected (Table 1) suggests that the within-plot spatial variability in SOM content hampered the detection of such a decrease. However it suggests also that the decomposition rate of SOM in the experimental plots is low enough to be confident that no substantial losses have to be expected as a consequence of the establishment of the plantation, a problem observed in many sites.
4.2. Biochemical fractionation of soil organic matter
4.2.1. Carbohydrates:
The relationship between carbohydrate content and total organic matter (measured by organic carbon) was highly variable, and strongly site-dependent (Table 2). Thus, the correlation between organic carbon content and relative richness in carbohydrates (in either WS, LP1 or LP2 pools; see 1.5.2 for a description of these fractions) was either positive or negative, depending on site and position within the soil profile.
Table 2. Correlation index (r) between total organic carbon (in %) and carbohydrate content (mg sugar C per g organic carbon).
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 10-20 cm 0.241 ns 0.358 * – 0.554 ***
2 10-20 cm 0.445 ** 0.215 ns – 0.498 **
3 10-20 cm 0.207 ns – 0.055 ns – 0.319 *
5 10-20 cm 0.063 ns 0.014 ns – 0.236 ns
7 10-20 cm – 0.344 * – –
1 0-10 cm – 0.086 ns – 0.127 ns – 0.398 *
2 0-10 cm 0.370 * – 0.622 *** – 0.008 ns
3 0-10 cm – 0.156 ns 0.124 ns – 0.301 †
5 0-10 cm – 0.087 ns 0.220 ns – 0.208 ns
7 0-10 cm – 0.291 † – –
The most consistent result was a negative relationship of total organic carbon content with the abundance of carbohydrates in LP2, the cellulosic ones. The lower the soil organic matter content, the higher the relative proportion of cellulose. This relationship was consistently negative, albeit it reached significance only in four cases out of eight tested.
For other indicators of carbohydrate abundance, either the sign was inconsistent, or reached significance in less than half the cases; thus they are not useful to detect trends in soil organic matter evolution. This is reflected further in the amounts of extracted carbohydrates, for which we did not detect any significant effect of any treatment.
The LP2 / total carbohydrates ratio (i.e. cellulose to total carbohydrates), an indicator of the richness of fresh plant-derived materials, ranged from about 3.5 % in Field trial 5 at 0-10 cm depth to about 25 % in Field trial 2, 10-20 cm depth. Thus the range of values (= the range in the degree of biochemical evolution of soil organic matter) is quite considerable. Values usually increased with depth: at 10-20 depth soil organic matter is more fresh, less evolved than at soil surface, obviously owing to the input of fresh roots. Again, no consistent effect of the technique against competing vegetation on this ratio was detected. As to the effect of soil conditioner, it was not detected in any case.
4.2.2. Phenolics:
The abundance of phenolics in LP1 is the most promising indicator of biochemical changes in soil (Table 3). The relationship with organic carbon content is consistently negative and always highly significant: the higher the organic carbon content, the lower the relative abundance of phenolics in this fraction. Sometimes the relationship is very high, particularly in semiarid field trials (1 and 2).
Table 3. Correlation index (r) between total organic carbon (in %) and the ratio of phenolics to total carbon (mg phenolic carbon per g of total organic carbon).
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 0-10 cm 0.051 ns – 0.748 *** – 0.184 ns
2 0-10 cm 0.281 ns – 0.795 *** – 0.593 ***
3 0-10 cm 0.392 ** – 0.414 ** – 0.099 ns
5 0-10 cm 0.017 ns – 0.422 ** – 0.001 ns
7 0-10 cm – 0.290 † – –
1 10-20 cm – 0.428 ** – 0.704 *** – 0.218 ns
2 10-20 cm 0.371 * – 0.708 *** – 0.575 ***
3 10-20 cm 0.043 ns – 0.710 *** – 0.179 ns
5 10-20 cm – 0.168 ns – 0.450 ** 0.191 ns
7 10-20 cm – 0.294 † – –
For other fractions the relationship is less clear (LP 2), or inconsistent (WS). In the hot-water extract the sign of the relationship was inconsistent (either positive or negative), thus not useful as indicator of biochemical changes.
The amounts of phenolics in the first hydrolysate (LP1), given in mg of phenolic carbon per gram of total organic carbon, ranged from 87 (Field trial 1, 0-10 cm) to 270 (Field trial 3, 10-20 cm). In the other extracts values were lower: usually less than 100 in LP 2, and less than 5 mg in WP. Differences associated to the treatment against competing vegetation were detected in some cases (e.g. Field trial 5 for the WS pool and LP 1, Field trial 2 for WS and LP 2, etc). In contrast, the addition of soil conditioners had no detectable effects.
4.2.3. Carbohydrate / Phenolic carbon ratio
The ratio between carbohydrate and phenolic carbon in the several labile pools (WS, LP1 and LP2) may serve as a complementary indicator for biochemical changes during decomposition. This index shows the proportion in these pools between easily decomposable substrates (in particular, carbohydrates) and substrates resistant to decomposition (phenolics as the most representative).
Table 4. Correlation index (r) between total organic carbon (in %) and the sugar carbon / phenolic carbon ratio.
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 0-10 cm – 0.116 ns 0.642 *** – 0.585 ***
2 0-10 cm 0.432 ** 0.765 *** – 0.329 †
3 0-10 cm – 0.166 ns 0.174 ns – 0.067 ns
5 0-10 cm 0.026 ns 0.205 ns – 0.101 ns
7 0-10 cm 0.216 ns – –
1 10-20 cm – 0.295 † 0.711 *** – 0.375 *
2 10-20 cm – 0.162 ns – 0.264 ns 0.291 †
3 10-20 cm –0.217 ns 0.362 * – 0.243 ns
5 10-20 cm 0.167 ns 0.296 † – 0.154 ns
7 10-20 cm 0.033 ns – –
The carbohydrate carbon / phenolic carbon varies depending on the pool. It is lowest in LP 2 (cellulosic hydrolysate), in which it ranges from about 0.1 (in Field trial 1) to almost 0.4 (in Field trial 3). The ratio usually increases with depth. In LP 1 the ratio ranges around 1-1.5 but differences between plots are noteworthy (e.g. values are unusually low for the field trial 3, < 0.5). Finally values are highest for the WS extract, the most easily decomposable pool, in which may be as high as 18 (Field trial 1).
The carbohydrate C / phenolic C ratio was never significantly affected by the application of soil conditioner. However it was sometimes significantly affected by the treatment against competing vegetation.
The relationship of this ratio with total organic carbon is almost always positive, and often significant (Table 4). This ratio is meant to reflect the biochemical quality of the main easily extractable fraction of soil organic matter, hence its quality as a substrate for soil microbial activity. The overall positive relationship with total organic carbon implies that the biochemical quality of this extractable pool will decrease as soil organic matter decomposes.
The biochemical quality of the second hydrolysate follows the opposite path; it is expected to increase with soil organic matter decomposition (negative relationship in most cases). However the number of significant correlations is lower, and therefore is less useful as indicator of biochemical change. Finally, the behaviour of the carbohydrate / phenolic carbon ratio in the water-soluble compartment seems largely affected by site.
4.2.4. Biochemical fractionation of soil organic matter: an overall view
Several of the studied parameters are good indicators of biochemical changes related to soil organic matter decomposition, and in spite of the short time of our experiment (less than two years of effective time) contrasted trends related to weeding treatments were already detected. We must expect that further soil samplings (foreseen in upcoming years) will allow for a more exhaustive description about how these changes affect soil biochemistry on the medium term.
A main result of our analyses is that the behaviour of many of the studied parameters depends on the site. The behaviour of the sugar / phenolics ratio for the WS pool, for instance, is not unique; the relative abundance of phenolics in WS pool also behaves differently from one site to another. Nevertheless, some of the studied parameters behave in a consistently similar way everywhere. The most clear is the abundance of phenolic compounds in LP 1, apparently the most promising indicator of biochemical changes with decomposition obtained in the biochemical fractionation protocole we applied.
In contrast, the addition of soil conditioner does not apparently result in biochemical changes in soil organic matter, relative to the control pits without any conditioner. This was somewhat unexpected, for this soil conditioner involves organic components which may serve as carbon source for the soil microflora (fungi and bacteria), and thus should have affected soil biochemistry somehow. The lack of any significant difference with the corresponding controls suggests that the expectable effects on the microbial activity of the soil conditioner are restricted to the very place where the conditioner was applied, i.e. the interface between the seedling root system and the surrounding soil.
4.3. Detection of specific compounds - Biochemical evolution of soil samples: study through TMAH-GC-MS
The thermochemolysis with tetramethylammonium hydroxyde, coupled with gas chromatography and mass spectrometry, was chosen as a technique for a global characterization of the soil samples, owing to the very high number of samples to be studied. This technique gives a global panoramic view about the chemical composition of the soil organic matter, and through the use of specific indicators, allows for a comparative evaluation of its biochemical evolution.
4.3.1. Fatty acids (FA) signature
Whereas plants produce FAs of all lengths, microbes produce virtually only short-chain FAs (< 20 carbons). Thus the ratio short to total FAs is an indicator of biochemical evolution of soil organic matter, more specifically the degree of microbial reworking.
In our soils, FA signatures are very high: 0.94 (Field trial 5), or 0.93 (Field trial 3). I.e. the very most of fatty acids (almost 95%) are short-chained. This points to a highly evolved lipidic pool, dominated by microbial-derived products. Whereas in Field trial 5 we did not detect any effect of sampling, in Field trial 3 the FA signature clearly increased with time: the setup of the experiment in Field trial 3 apparently accelerated this biochemical evolution. The FA signature was not affected by any treatment whatsoever.
4.3.2 Carbohydrate signature
While plants produce many structural pentoses, microbes produce very small amounts of them. The proportion between hexoses and pentoses (galactose + mannose ) / (arabinose + xylose) is a measure of the persistence of relatively undegraded, plant-derived tissue structures.
Values obtained in the soil samples of our experiment ranged between 16.8 and 2.3. They were highly variable, thus, which is not so strange taking into account that the presence of recently dead roots in a given soil sample may push this ratio to high values. Some effect of mulch type may be detected sometimes (e.g. in Field trial 5 in the first sampling, in the absence of soil conditioner); but the lack of consistency of these differences suggest that these effects were spurious. When considered all data altogether, no significant difference due to any treatment was detected. In Field trial 3, a significant effect of time was detected: the carbohydrate signature significantly decreased from the first to the second sampling.
4.3.3 Ratio ramified FAs / long-chain FAs
Ramified fatty acids are produced only by microbes. On the other hand, long-chain FAs (> 20 C) are produced only by plants. Thus the ratio between both may be a very sensitive indicator of biochemical evolution: the higher the ratio, the higher the degree of microbial reworking.
In our samples, the ratio ranges from about 0.9 (lowest value observed in Field trial 3) to 5.1 (highest value observed, in Field trial 5). No consistent effect of any treatment was observed. However the effect of sampling was clear and significant; the ratio increases with time at all sites, which indicates an active microbial reworking.
4.3.4 Phenolic compounds indicators
Most phenolic compounds in soil organic matter originate from lignin, the main polyphenolic polymer in plants. The biodegradation of lignin involves its depolymerization, but also oxidative processes by which their phenolic monomers are transformed: the aldehyde forms are oxidized to acidic forms. Within a given family of phenolic compounds (guaiacyl, syringyl), an increase in the acidic / aldehyde ratio is to be expected during lignin degradation.
No such an increase was observed for the guaiacyl phenolics; for siringyl phenolics, instead, a clear decrease was observed in Field trials 5. Thus apparently the degree of lignin oxidation decreased there: this is a surprising result, to be confirmed in future samplings. Alternatively, it could be due to the release into the soil of dead tissues, root-derived, rich in fresh and relatively undecomposed lignin.
4.3.5. Overall view
We detected signs of biochemical evolution with time in our samples. Overall such a detection shows how TMAH-GC-MS technique is more sensitive than the biochemical fractionation for the detection of microbial-driven evolution of soil organic matter, even when (as shown previously) the variability in soil organic matter content hampers the direct detection of organic matter mineralization.
The lack of any significant effect of neither soil conditioner presence nor groundcover type on the biochemical composition of SOM as studied by TMAH-GC-MS, however, suggests that, at least apparently, the differences in water availability and/or thermal regime in soil originated by the several groundcover / weeding techniques types do not generate contrasting paths in the biochemical evolution of soil organic matter, at least in the term studied in this project (< 2 years of effective study). We cannot discard that in future samplings more relevant differences between treatments could be observed.
4.4. Environmental implications
The lack of strong, significant differences in the biochemical features of soil organic matter relative to the controls indicates that neither the tested weeding techniques nor the soil conditioner application release into the soil organic matter any deleterious compound in detectable amounts. The natural soil biochemistry seems not affected, leaving aside a (probable, to be confirmed in future samplings) acceleration of SOM decomposition due to the increased water availability.
In fact, a main observation in the TMAH-GC-MS study was the lack of any detectable signal of extraneous compounds which could be attributed to any plastic or synthetic material used in the groundcovers or in the soil conditioner. These components do not penetrate into the soil to a detectable level: if present, they are retained by the groundcover itself, or – in the case of compounds derived from the soil conditioner – they are restricted to the very perimeter of the seedling root system.
This observation has obvious implications relative to the safety of the applied treatments. No potentially toxic compounds have been detected in soil organic matter, during these two years of the SUSTAFFOR project.
5. Main results related to groundcover durability / degradability study
5.1. Degradation of the full plate biodegradable groundcover (DTC)
5.1.1. Artificial weathering
Since thicker materials were tested the more aggressive QUV-B illumination (shorter wavelength, more aggressive UV light) was chosen. Tests were performed up to 2000 hours.
A first observation is that there is a drastic reduction of the strain percentage after a first period in the Q-UV chamber. This reduction is not due to a real degradation effect but is due to a (re)crystallisation process. Immediately after the production the bioplastic largely remains amorphous but as function of time and especially at raised temperatures the polymer will crystallise. This results in a reduction of strain; the material becomes stiffer and somewhat more brittle. Since flexibility is most important during installation the increased stiffness will be of limited importance.
A second observation is that due to the very aggressive UV-B light, also a severe reduction in tenacity is observed. The material retains ± 30% of its original strength after 2000 hours in the QUV-B test. Still the product keeps its full integrity and therefore its functional potential.
5.1.2. Weathering in field conditions
Similar observations are made for the strain at break during field weathering tests. After the first sampling (6 months after installation) a sharp drop in percentage of strain is observed again and can be assigned to the recrystallization of the polymer. This has however no real effect on the performance of the material.
In contrast to the artificial weathering under QUV-B conditions, it is observed that the tenacity properties are hardly reduced during the field tests. Only a minor reduction in tenacity is observed after 18 months in the fields. Via extrapolation it is to be expected that the effective lifetime of these groundcovers will probably be above 5 years certainly if only degradation by light is taken into account. Only a time dependent important increase in microbiological attack could speed up the degradation. After 18 months in the field, there is no proof for such in infestation found yet. The differences observed between climate zones are limited and not statistically relevant.
So it is concluded that the injection moulded bioplate groundcover, resist degradation under real weathering conditions very well and it is likely that the material will retain its functionality up to 5 years or even more.
5.2. Degradation of the groundcover made of a biofilm with injection moulded rim (DTC)
The rim material is similar to the one used for the bioplate, so durability properties are the same as well and were not evaluated again. In the following tests we concentrate on the properties of the commercial biofilm used as mulch material.
5.2.1. Artificial weathering
For this thin film material QUV-A tests were performed.
The properties of the original biofilm are strongly resembling the once of a reference PE-foil that can be used as groundcover. However in this case a severe drop in properties is observed as function of the artificial weathering in the QUV-A test conditions. After 1000 hours QUV-A the elongation at break is reduced to 25%. After 2000 hours these film materials are so brittle that they are difficult to handle and are even damaged when preparing samples for testing. Further testing is becoming impossible although the intrinsic tenacity was only reduced by 50%. Based on these results it can already be expected that the film will have an insufficient resistance for
long term usage.
5.2.2. Weathering in field conditions
Field tests are acknowledging that the selected commercial biofilm has a limited and insufficient durability. After 1 year most of the film material was either damaged or was so weak that mechanical tests could hardly be performed.
Therefore it should be concluded the selected biofilm can maximum survive 1 year in field tests and is not appropriate to be used for groundcover application in forestation where several years of retained functionality is requested. Alternative biofilms, differing in composition, are available in the market with a much longer durability. The possibility of combining a biofilm with an injection moulded biopolymer rim still can be maintained if an appropriate biofilm with a high durability is selected.
5.3. Degradation of the groundcover made of woven jute treated with bioresin (La Zeloise)
5.3.1. Artificial weathering
For the Jute materials both reference jute fabric without additional treatment, as well as the novel developed bioresin treated groundcover were evaluated in the artificial weathering test. Due to the aggressive conditions a fast drop in mechanical properties of the materials is observed. The novel bioresin treated material, shows a considerably improved stability, as can be observed in figure 2. Due to the initial high tenacity of the Jute fabric the resin treated material still has a sufficient tenacity to retain its functional integrity.
5.3.2. Weathering in field conditions
Due to influence of water, illumination and microorganisms, jute has a limited durability when used in the fields. In southern countries like Spain the lifetime of a standard jute groundcover is often not more than 1 year. In the trials of the project, although a fast reduction in tenacity is observed for the jute based groundcover, the material retained its integrity thanks to the initial high strength of the fabric. The groundcovers were still largely intact after 18 months unless damages were made by wildlife (e.g wild boar). The tenacity after 18 months is still of the same order or even higher than the original strength of groundcovers based on PE-film (± 40 N). So the material keeps its functionality, if no external forces are put on the material. Nevertheless it can be expected that the material, will lose its functionality during the third season. Therefor we can conclude that bioresin treated jute fabric will resists biodegradation during 2, maximum 3 years, in function of the climate circumstances.
5.4. Degradation of the groundcover made of recycled rubber (EcoRub)
5.4.1. Artificial weathering
Since it is expected that the material has an extremely long lifetime, artificial durability tests were performed with the more aggressive QUV-B test conditions. As can be expected for a rubber material, the product has a high elongation at break, a rather low e-modulus and a high tenacity. Although some fluctuations are observed only a limited tendency for a reduction in elongation at break and tenacity is observed after 2000 h of aggressive Q-UVB treatment. Since under these harsh conditions only a minor reduction in properties is observed we can already expect by extrapolation that such materials well be extremely durable.
5.4.2. Weathering in field conditions
No or only minor fluctuations in properties like tenacity and elongation modulus can be observed. Also strain is hardly influenced by the field tests after 18 months. The limited variations are largely based on variation in between samples and cannot be assigned to significant differences due to variations in function of time or in between climate zones.
It is concluded that after 18 months, the rubber groundcovers have fully kept their original properties and no significant deterioration of properties can be observed. Long-term extrapolation is difficult to make based on a 18 months field trial but in combination with the minor changes observed in the 2000 h tests under QUV-B conditions , it can be expected that the rubber mats will survive extremely well, and will last for probably more than 10 or even 15 years in outdoor applications. This implies that the material could be reused in several consecutive plantation trials or can be used as a permanent groundcover in for instance urban landscaping applications.
6. Main conclusions about each novel technique
6.1. Innovative soil conditioner (TCU+20G, TCU+40g, TCU+80g):
- The innovative soil conditioner had a positive effect especially in sites limited by the poor and light soil (Semiarid and Montane conditions), especially where water deficit is severe (the former, field trials 1 and 2). In these conditions, this technique improved survival and aerial and subterranean growth rates, as well as water status. In Montane conditions the most relevant positive effect was detected on tree growth.
- In rich sites, with fertile and heavy soil and well provided with water this technique did not have in general a remarkable effect, and only survival rate in Field trial 4 was improved.
- The innovative formulation led to results in general similar to the commercial version of TerraCottem Universal, indicating that it represents an interesting alternative to it. Moreover, it provided generally better results than the alternative soil conditioner tested in Field trial 4 (Hydrogel and Peat).
- The dose prescribed for small to medium sized seedlings (40 g/tree) seem to be the most cost-effective, provided that in general it leads to better results than the lower dose (20 g/tree) and generally not worse than in the case of the higher dose (80 g/tree).
6.2. Biodegradable full plate biopolymer groundcover (FULLPLATE)
- This technique was only tested in Field trials 7 and 8, and not for all variables. This technique provided in general results similar to those from BIOPOLYMER.
- This product seems to have an adequate durability, estimated in around 5 years.
6.3. Biodegradable framed biopolymer groundcover (BIOPOLYMER)
- This technique proved being an interesting option for increasing above and belowground growth in all the conditions tested, compared to NoWeeding trees, to CommHerbicide, to CommBiofilm and, to a lesser extent, to CommPE. This product also led to an increase in soil moisture in highly productive conditions, compared to NoWeeding and to CommHerbicide, and compared to CommBiofilm in the limiting conditions of Field trial 7.
- It can be accepted that this technique has a performance (tree fitness, soil moisture) similar an often superior than the commercial alternatives.
- The only limitation of this technique is the need to fuse the frame to a more resistant biofilm than the version utilized in these field trials, in order to guarantee an acceptable durability.
6.4. Biodegradable woven jute groundcover (JUTE)
- This technique provided results superior than NoWeeding in both limiting and productive sites, with regard to aerial and belowground tree growth. It also increased tree water status in productive conditions.
- The results (tree performance, soil moisture) were similar and often superior to alternative techniques to control competing vegetation: compared to Commherbicide, this technique resulted in higher tree aerial and belowground growth, although the effects with regard to soil moisture and tree water status are not clear. Finally, this technique resulted in higher tree belowground and aerial growth than CommBiofilm in most sites, and also increased soil moisture in semiarid conditions.
- The durability of this technique can be limiting in the case of highly aggressive conditions (high level of UV radiation, sunshine, wind and weed development), with an expected service life of around 3 years. In less aggressive conditions it could have sufficient durability, thanks to the resin treatment.
6.5. Recycled rubber groundcover
- Compared to NoWeeding, this technique resulted in increased tree growth (both aerial anb belowground) in all the conditions tested. Moreover, it led to enhanced soil moisture in areas with severe water deficit (semiarid sites).
- The results were similar and often superior to alternative techniques to control competing vegetation, leading to higher aerial and belowground growth rates than CommHerbicide in productive sites and, less evidently, than CommPE and CommBiofilm in limiting and productive conditions, respectively. It led to higher soil moisture compared to CommHerbicide and to CommBiofilm in most sites, but to lower soil moisture compared to CommPE in general.
- The durability of this technique is expected to reach 15 years, which is an excellent figure for long-term applications including landscaping and gardening.
7. Economic study on the potential interest of soil conditioners and groundcovers in tree planting
7.1. The cost analysis
In the framework of the preparation of the Technical Guide “Soil conditioners and groundcovers for sustainable and cost-efficient tree planting in Europe and the Mediterranean”, done in the framework of Sustaffor project, a cost analysis on the use of the novel techniques and reference techniques was performed. The aim was to assess the potential of these techniques if the choice of the tending operations and plantation techniques depends only on economical criteria, not considering the environmental advantages brought by the novel techniques.
The assumptions of the models were based on real practical data from the use of the techniques (installation productivity rates) and published costs. Different tree planting scenarios were considered, with regard to site accessibility and, in the case of techniques to control competing vegetation, site productivity.
The accessibility scenarios, considered for all techniques, were:
- Flat, easily accessible site. Each round trip to the site for the staff installing or applying the techniques takes 40 minutes.
- Moderate slope (10-20%), intermediately accessible site: each round trip takes 80 minutes and the productivity rate for all activities is reduced compared to the previous scenario.
- Steep slope (30-50%), poorly accessible site: each round trip takes 120 minutes and the productivity rate for all activities is further reduced.
In the cost analysis of techniques aiming at controlling competing vegetation three different levels of site productivity were considered, involving a variable number of required weeding interventions:
- High productivity: weeding is applied twice in years 1, 2, 3 and 4, and once in year 5.
- Medium productivity: weeding is applied once in years 1, 2, 3, 4 and 5.
- Low productivity: weeding is applied once in years 2 and 5.
In chapters 7.2. and 7.3. we present more detailed information from the overall service costs of the different techniques, subject to the different scenarios.
7.2. Cost analysis of techniques aiming at mitigating drought impact
The techniques considered were the application of one and two emergency irrigations and the use of soil conditioner at two doses: 40 g/tree and 100 g/tree. The conclusions of the analysis were the following:
- In all cases, the application of a soil conditioner at the dose prescribed for small to medium sized seedlings (40 g/tree) is cheaper than one emergency irrigation. The difference becomes more evident as accessibility gets intermediate or poor. Only when planting a large number of trees in easily accessible sites the unitary cost of one irrigation is similar to the cost of soil conditioning application at this dose.
- The application of soil conditioner at 100 g/tree dose (prescribed for large seedlings) is more expensive than one emergency irrigation, although for a low number of trees in areas with intermediate to poor accessibility the cost is similar.
- In all cases the application of two emergency irrigations is the most expensive technique.
- Soil conditioning is much less dependent on labour costs than emergency irrigation. The application costs of soil conditioning at the indicated doses vary less than 30% between 12 €/h and 24 €/h labour costs, while the figure rises up to 70% in the case of emergency irrigation.
- The preference for soil conditioning over emergency irrigation becomes more evident as labour costs increase (24 €/h), with the 100 g/tree dose comparable to 1-time irrigation in small plantings at intermediate accessibility sites. However, with cheap labour costs (12 €/h) soil conditioning at the 40 g/dose results in similar costs to one irrigation in easily accessible areas.
- Thus, soil conditioner is an economically feasible alternative to emergency irrigation.
7.3. Cost analysis of techniques aiming at controlling competing vegetation
The techniques considered were the following: mechanical weeding with man-operated tools, chemical weeding (both repeated, reference techniques), plastic groundcover (reference technique), Long-lasting groundcover at two retail price levels (4.5 and 6 €) and biodegradable groundcover at two retail price levels (2 and 3 €). The conclusions of the cost analysis were the following:
- In low productivity sites, where the number of weeding interventions required is low (two or less), mulching is not a suitable option.
- In medium productivity sites, with an expected need for annual weeding during the first five years, herbicide application is the cheapest option although in poorly accessible sites the results are somewhat similar to plastic mulching and to 2 € biodegradable groundcover. In the case that the use of herbicide is restricted, the use of plastic mulching is cheaper than mechanical weeding. The cost of using the 2 € biodegradable or the 4.5 € long-lasting mulch is similar to mechanical weeding in sites with good accessibility, and lower in intermediate to poorly accessible sites. In the latter, even the 3 € biodegradable mulch leads to costs similar to mechanical weeding.
- In highly productive sites, requiring frequent weeding interventions, mulching is the cheapest option. Only the most expensive units (6 € long-lasting and 3 € biodegradable) in easily accessible sites have costs similar to herbicide application.
- The cost of utilizing 4.5 € long-lasting mulches leads to results similar to 2 € biodegradable groundcovers in easily accessible sites, while in intermediate sites the biodegradable option is cheaper. The 6 € long-lasting groundcover provides lower costs than the 3 € biodegradable mulch.
- The attractiveness of biodegradable mulches depends largely on their retail costs. A retail cost of 2 € becomes comparable to 0.9 € plastic mulching in intermediate access sites, and the cost differences are even smaller for poorly accessible sites. The biodegradable units with a retail price of 3 € are not competitive with plastic mulching, according to the analysis. It should be stressed that this analysis does not take into account the environmental and social advantages of the biodegradable groundcovers, which are increasingly taken into account in tree planting.
- The cost of using groundcovers is much less dependent on labour costs than recurrent weeding techniques. The increase in costs of using biodegradable mulches when increasing labour costs from 12 to 24 €/h amounts to 20% while in the case of mechanical and chemical mulching the increases are 65% and 75%, respectively. Both reusable and plastic mulching correspond to increases of around 50% when considering the mentioned rise in labour costs.
- In low productivity conditions mulching remains as an economically unsuitable option compared to chemical or mechanical weeding at any labour cost.
- In medium productivity conditions plastic mulching shows intermediate costs falling between mechanical and chemical weeding at all labour costs, while the economic feasibility of other techniques vary considerably:
* With a high dependence on site accessibility, the cheapest labour costs (12 €/h) makes mechanical weeding falling to lower, similar or higher costs in sites with good, intermediate and poor accessibility (respectively) compared to both 2 € biodegradable mulching and 4.5 € long-lasting mulching.
* With high labour costs (24 €/h) the cost of chemical weeding is lower, similar or higher in sites with good, intermediate and poor accessibility (respectively) as compared to 2 € biodegradable mulching. At this labour cost, the 3 € biodegradable mulch is an alternative to mechanical weeding in sites with intermediate (similar costs) and poor (lower costs) accessibility.
- In high productivity conditions mechanical weeding is the most expensive technique at all labour cost levels. Plastic mulching is cheaper than herbicide application in all cases, while 2 € biodegradable mulching is also cheaper than herbicide application except in easily accessible sites for the lowest labour cost level.
- Among mulching techniques, the use of plastic groundcover leads to the best economic results at the low labour cost level (12 €/h), followed by 4.5 € long-lasting mulching. However, at the highest labour cost level (24 €/h) plastic mulching results in costs similar to or higher than 2 € biodegradable mulching in intermediate and poor accessibility sites, respectively.
- It can be concluded that both biodegradable and long-lasting groundcovers are an economically feasible alternative to reference weeding techniques under certain circumstances.
8. References
Grasset L., Rovira P. & Amblès A. 2009. TMAH-preparative thermochemolysis for the characterization of organic matter in densimetric fractions of a mediterranean forest soil. Journal of Analytical and Applied Pyrolysis, 85, 435-441.
Nelson D.W. & Sommers L.E. (1996): Total carbon, organic carbon, and organic matter. In: D.L. Sparks (ed), Methods of Soil Analysis, Part 3: Chemical Methods. 3rd. Ed. SSSA Book Series nº 5. Madison, USA. pp. 961-1010.
Rovira P., Duguy B. & Romanyà J. 2012. Long-term effects of wildfires on the biochemical quality of soil organic matter: a study on mediterranean shrublands. Geoderma 179-180, 9-19.
Potential Impact:
1. Potential impact
The potential impact of the project is related to the opportunities (technical and socio-environmental, and resulting market ones) that the novel techniques developed during the project imply.
1.1. Technical and socio-environmental opportunities
The novel techniques developed during the project represent new alternatives for mitigating the negative effects of drought and competing vegetation, two of the main threats to tree planting in our conditions, for all types of tree planting projects.
- The new soil conditioner is applied at the moment of planting and represents an alternative to repeated emergency irrigations that result in a massive use of water and fossil fuels.
- The new biodegradable groundcovers are also applied right after planting, allowing optimizing the labour and time resources. These techniques are an alternative to repeated and polluting weeding interventions such as mechanical (i.e. utilizing hand-operated or tractor-pulled machinery) and chemical (using herbicides) weeding, and to plastic mulching, which must be removed at the end of its service life and is built on non-renewable raw materials.
- The new long-lasting groundcover is also an alternative to repeated weeding interventions, and offers the possibility of long-term (e.g. 15 years) use in a single place, or can be reutilized in different areas in shorter periods of time.
As shown in the summary of project results, these techniques have proven to be highly performing, with results similar and often superior to reference (often less sustainable) techniques. Moreover, all of them have areas of application where they are economically cheaper than the reference techniques, and thus there is a market gap where these techniques can be promoted.
Therefore, these techniques and especially the new soil conditioner and the new biodegradable groundcovers are particularly interesting for the following cases:
- Hardly accessible areas: sites located far from populated areas and/or in uneven land or steep slopes, where the application or most reference techniques relying on repeated interventions (emergency irrigation, mechanical or chemical weeding) are expensive to apply.
- Areas where the use of machinery (noise, vulnerable soil or vegetation, etc), plastic mulches or herbicides is restricted by legal, ecological or social constraints: protected areas, parks and gardens, sites with high visual impact, etc.
- Minimal management schemes: areas where it is possible to apply reference techniques (emergency irrigation, mechanical / chemical weeding) but it is intended to reduce their number and intensity because of practical purposes.
- Managers that are open to invest more resources at the beginning of the project if it allows minimizing the time and resources invested during the following years.
- Small tree planting projects, where the unitary cost of any tending operation is high.
1.2. Market opportunities for each novel technique (exploitation of results)
The above mentioned technical and socio-environmental advantages result in market opportunities comprising all the depicted situations, in a range of different types of tree planting: protective forestry (forest landscape restoration, protection of soil and water resources, biodiversity conservation), productive forestry (timber, biomass, cork, nuts, game...) fruit tree planting, landscaping, home gardening, tree nurseries, etc.
The main market opportunities of each novel technique are the following:
1.2.1. New soil conditioner
1.2.1.a Cost level
Price similar to current best-available soil conditioner (Terracottem Universal)
1.2.1.b Key market messages
- Polyacrylamide-free soil conditioner.
- Proprietary mixture of more than twenty components each from different groups all assisting in the plant growth processes in a synergetic way.
- Biodegradable with no toxic degradation products. Expected extended lifetime of ± 8 year.
- 1-time application during planting of trees, avoiding repetitive irrigation during drought periods.
- Proven improved survival rate and growth performance (up to factor 3) for planted trees in soils with poor water and nutrient holding capacity, especially when subject to seasonal water deficit.
- High water absorption capacity and water and nutrient available for the tree offered by the “TerraCottem Universal Plus formulation”.
- Scientifically supported field trials proving the performance;
1.2.1. c Main target markets
- Re/afforestation: all types of productive and protective plantations.
- Urban and private landscaping.
- Nursery production.
1.2.2. Biopolymer-based groundcover, full plate (dimensions foreseen: 50x50 cm)
1.2.2.a Cost level
Intermediate, similar or slightly higher than other biodegradable groundcovers.
1.2.2.b Key market messages
- Fully biobased
- Biodegradable with no toxic degradation products; no removal costs or remaining long-term litter.
- Expected minimum performance service life of ± 5 years for the biopolymer full plate and for biofoil with injection moulded biopolymer rim if biofoil is selected appropriately
- No need for mechanical or chemical weeding (reduced maintenance costs)
- The foil or plate reduces transmission of air and water (humidity).
- Complete blockage of weed growth.
- Easy to install if the design of the plate is appropriately adapted.
- Colour can be selected; dark colours tend to accumulate heat, light colours reflect the sunlight.
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Scientifically supported field trials prove the performance superior to unweeded trees, generally better than herbicide application and similar to standard plastic mulching.
1.2.2. c Main target markets
- Re/afforestation: due to raised cost level and limited size only applicable for plantations with trees of a high cost range and slow growth, requiring at least 5 years without significant weed competence
- Potential for productive plantations and urban landscaping
1.2.3. Biopolymer-based frame groundcover (DTC)
The company producing the framed biopolymer groundcover (DTC) has decided, for the moment, not putting this product in the market, until finding a suitable commercial layer to which fusing the frame.
1.2.4. Biodegradable woven jute treated with bio-resin
1.2.4.a Cost level
Similar to commercially available biodegradable films, which is approximately the double of a polyethylene film.
1.2.4.b Key market messages
- Fully biobased (both resin and fibre).
- Biodegradable with no toxic degradation products (degrades within ± 3 years, depending on the site conditions).
- Expected extended service life of ± 3 years. Material fully disintegrates and acts as organic compost. Avoids removal costs or remaining long term litter.
- Offers ecologic and economic alternative for chemical & mechanical weeding
- No need for mechanical or chemical weeding (reduced maintenance costs)
- Permeable to air and water at the root zone. Proven positive impact on root growth
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Easy to install.
- Natural aesthetic look, easily “integrates” in the natural environment.
- Size and shape can be changed on the demand of client
1.2.4.c Main target markets
- High application potential in re/afforestation, both productive and protective
- Urban landscaping and areas with high visual pressure
- Weed control only required during first 3 years: fast-growing trees, possibility to perform further weeding interventions.
1.2.5. Long-lasting groundcover made of recycled rubber (dimensions foreseen: 40 cm diameter)
1.2.5.a Cost level
High, around 4 times higher than polyethylene film
1.2.5.b Key market messages:
- Fully produced from recycled materials (offering a second life to rubber wastes).
- Durable material with expected lifetime of at least of up to 15 years under outdoor conditions, and to be reused during several plantation cycles. After useful lifetime, the groundcover should be recovered from the field and reused in new plantations (unless long-term prevention of weed growth should be guaranteed for longer e.g. trees in an urban environment).
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Closed foil or plate reduces soil water evaporation.
- Complete blockage of weed growth, due to its dense structure.
- Easy to install, self-laying potential due to density of 2.9 kg/m².
- Black colour prevents penetration of light and results in accumulation of heat underneath the plant.
1.2.5.c Main target markets
- Landscaping for long-term suppression of weed growth near the stem of a tree (thus it can be an excellent complement to mechanical weeding or mowing, avoiding tree damage).
- Reusable pot discs (small sizes) for nursery applications
2. Dissemination activities
2.1. Objectives of dissemination
The dissemination activities performed during the project have followed a range of objectives:
- Raise awareness about innovative techniques for more efficient and sustainable tree planting, alternative to the limited current options. The target groups are the society in general, practitioners and managers, companies, researchers and policy makers.
- Create a space for open discussion among managers and technicians about the need for developing new methods for tending and managing tree planting projects
- Introduce the novel techniques, their rationale, performance and opportunities
- Increase the capacity of the SMEs participating in the project for exploiting commercially their products from an eco-innovation prospective
2.2. List of Sustaffor dissemination activities
The main dissemination activities were the following:
2.2.1. Webpage: the webpage is the basic infrastructure for project presentation and dissemination of results and outcomes, worldwide. It is programmed in both English and Spanish. The address is www.sustaffor.eu. It has been updated regularly with the main events and preliminary results of the project, and has been disseminated in all the public events where a Sustaffor partner has participated. It is expected to keep it online during at least 5 years.
2.2.2. Brochure: an 8-pages brochure was prepared in both electronic and paper versions (2,000 units), introducing the project concept, aims, novel techniques, partners and experimental activities. The paper version was distributed in all the activities where a Sustaffor partner has participated. An additional version of the electronic version was produced in Spanish. Moreover, the electronic version of the brochure was updated at the end of the project, with a new 12-pages format including a summary of the results of the field trials and a final page with the conclusions.
2.2.3. Roll-up: a roll-up summarizing the project was provided to each SME, to be utilized in all the commercial fairs where they participate.
2.2.4. Final seminar: the project and its main outcomes were presented on December 16th, 2015 in Solsona (Spain). The audience included members of the Catalan and Andorran public administration, forest, agriculture and gardening companies and forest and agriculture owners. Professor Jordi Cortina, Head of the European Chapter of the Society for Ecological Restoration was invited as guest speaker.
2.2.5. Individual novel techniques leaflets: a 2-page leaflet was produced for each company, where the main technical and environmental advantages of each novel technique are presented. These documents have a clear commercial orientation. They are produced in electronic and paper format, in English, Spanish, French and Polish.
2.2.6. Video-presentation: A 4.5 minutes video has been produced for the broad dissemination of Sustaffor activities and results. This video has been located in the project webpage and has been provided to all the partners for its dissemination.
2.2.7. Newsletters: five periodic electronic newsletters, with 5 to 12 pages each, were produced and sent by e-mail to the professional distribution list of each partner.
- Newsletter 1: Sustaffor project launched! (February 2014)
- Newsletter 2: Sustaffor field trials accomplished! (May 2014)
- Newsletter 3: Sustaffor field trials monitoring (March 2015)
- Newsletter 4: Some preliminary results from the first vegetative period (July 2015)
- Newsletter 5: Sustaffor comes to an end...here are some of the main conclusions (December 2015)
2.2.8. On-field workshops: taking place in the field trials, these half-day technical meetings allowed introducing and discussing the concept and aims of the project to end-users and managers, as well as the experimental design, available results and how to install and manage the novel techniques. The two on-field workshops were:
- Reforestació de terrenys agrícoles a mínim cost (June 2015)
- Noves tècniques de plantació d?arbres: sostenibilitat i eficiència (December 2015)
2.2.9. Trade fairs: the SMEs have presented their involvement in an EU-funded research project, as well as the novel techniques developed, in seven different trade fairs of national and international level. Most of them were performed by the SMEs commercializing the products (Ceres and Terrezu). The fairs were:
- Gardenia 2014 (Poznan, Poland, February 2014)
- Green if Life 2014 (Warsaw, Poland, August 2014)
- International Gardening Days 2014 (Goluchow, Poland, September 2014)
- GreenExpo 2014 (Gent, Belgium, September 2014)
- Gardenia 2015 (Poznan, Poland, February 2015)
- Green if Life 2015 (Warsaw, Poland, August 2015)
- Bionoain 2015 (Noain, Spain, September 2015)
2.2.10. Training activities: these training are addressed at the SMEs participating in the project and to their commercial partners that they invited to participate. In both cases the training was performed by CTFC staff and guest speakers.
The first training took place in Poznan (Poland) in February 2015, during the international fair “Gardenia”. The topic was “Reforestation in Europe: trends, techniques and economics”. The guest speaker was Francisco Lario, from the Spanish public company TRAGSA.
The second training took place in Navarra (Spain) in October 2015, titled “Performance of Sustaffor novel techniques, labelling, market opportunities”. The guest speakers were Anna Esteve, expert on eco-labelling from the Catalan public administration, and Gregorio Borge, from the Spanish SME Zicla, specialized on the fabrication of eco-friendly products.
2.2.11. Appearances in Mass media_ a set of five press releases addressed to the mass media have been prepared, in order to disseminate the project and its outcomes among the broad public. Moreover, two participations were performed in radio and TV.
Following this link, it is possible to check the TV programme broadcasted in the Catalan TV:
http://www.ccma.cat/tv3/alacarta/programa/Arbres-Solsona/video/5224971/
Following this link, it is possible to check the radio program where Míriam Piqué, project coordinator, was interviewed:
http://www.ccma.cat/catradio/alacarta/informatius-catalunya-radio/el-primer-sector-la-gamba-de-palamos-de-la-barca-a-casa/audio/906343/
2.2.12. Participation in technical conferences: the RTDs have participated in (or submitted communications to) eight high-level technical conferences, either with posters or oral communications. The conferences are held at different geographic and thematic approaches. These technical conferences were:
- EU 1st Textile Flagship Conference (Brussels, October 2014)
- Meeting on European Funding for SME innovation (Solsona, December 2014)
- IV Mediterranean Forest Week (Barcelona, March 2015)
- Euratex 2015 (Brussels, March 2015)
- Reforestation Challenges (Belgrade, June 2015)
- SISEF National Congress (Florence, September 2015)
- III Joint meeting of the Spanish Society of Forest Sciences – Working Group on Afforestation and the Spanish Association of Land Ecology (Lugo, October 2015).
Moreover, an abstract was submitted to the 21st International Symposium on Analytical and Applied Pyrolysis, to be held in Nancy in May 2016.
2.2.13. Technical guide: “Soil conditioners and groundcovers for sustainable and cost-efficient tree planting in Europe and the Mediterranean”. This manual, oriented to final-users and managers, presents the challenge of tree planting in Europe and the Mediterranean and options for tackling drought and competing vegetation, including a cost analysis of various options. A special focus is done in the potential of the novel techniques developed during the project. It has been produced in Spanish (electronic and paper versions), English (electronic) and French (electronic).
2.2.14. Articles in technical journals: during the project, seven technical papers have been produced and published or submitted to different technical journals related to forestry, environmental sciences, landscaping and agriculture, with various geographical scopes. In these articles, the project and its main outcomes and results were presented, addressed to technical public of different background: policy makers, managers, practitioners and companies. Moreover, the publications in the proceedings of the mentioned conferences (2.2.13) are also considered in this group of publications. The list of technical papers is as follows:
- Coello J, Rovira P, Fuentes C, Piqué M. (2016). Eficacia y sostenibilidad en restauración forestal: nuevos acondicionadores y cubiertas del suelo. Proceedings of the III Joint meeting of the Spanish Society of Forest Sciences – Working Group on Afforestation and the Spanish Association of Land Ecology (Lugo, October 2015). Press
- Coello J, Piqué M. (2016). Condicionadors i cobertes del sòl per a plantacions forestals més sostenibles i eficients. Silvicultura (press)
- Coello J, Piqué M, Rovira P, Fuentes C. (2016). Intérêt de l’amendement et du paillage pour les plantations forestières en région méditerranéenne : le projet FP7 Sustaffor. Forêt-Méditerranéene (press)
- Coello J, Cortina J, Valdecantos A, Varela E. (2015). Forest landscape restoration experiences in southern Europe: sustainable techniques for enhancing early tree performance. Unasylva 245 (66): 82-90
- Coello J, Rovira P, Fuentes C, Piqué M. (2015). SUSTAFFOR project: soil conditioners and groundcovers for tree planting (Proyecto SUSTAFFOR: acondicionadores de suelo y acolchados para plantaciones forestales). Navarra Forestal 37: 35-37
- Coello J, Piqué M, Rovira P, Fuentes C. (2015). Innovation in sustainable afforestation techniques (Innovació en tècniques sostenibles de reforestació). Catalunya Forestal 126: 5-10
- Coello J, Fuentes C, Piqué M. (2015). Innovative soil conditioning and mulching techniques for forest restoration in Mediterranean conditions. In: Ivetic V., Stankovic D. (eds.) Proceedings: International conference Reforestation Challenges. 3-6 June 2015, Belgrade, Serbia. Reforesta. 201-210.
2.2.15. SCI journals: three scientific papers (peer-reviewed in indexed journals) have been produced and submitted in December 2015, being addressed at researchers. These publications have been coordinated by CTFC and CNRS, and are based on the results from the field and laboratory trials. The list of papers are as follows:
- Vitone A, Coello J, Piqué M, Rovira P. (2016). Use of soil conditioners and mulching innovative groundcovers in Mediterranean re/afforestations: aerial and belowground effects in hybrid walnut. Submitted to iForest
- Coello J, Fuentes C, Rovira P, Piqué M. (2016). Improving seedling survival and growth in mountain forest restoration: combined effect of mulching and soil conditioners. Submitted to European Journal of Forest Research
- Abdelli G, Al Husseini A, Rovira P, Grasset L. (2016). Thermochemolysis for the simultaneous analysis of the main biomolecular families in soil. application to the mesurement of the impact of inovative renewable practices for reforestation in a climate change context. Submitted to Journal of Analytical and Applied Pyrolysis
List of Websites:
The project webpage is www.sustaffor.eu
Contact details of the coordinator (CTFC):
Project coordinator: Míriam Piqué
Technical manager: Jaime Coello
Administrative and financial coordinator: Dúnia Riu
sustaffor.info@ctfc.cat
Phone: +34 973 481 752
According to FAO (2010), 12 million ha are afforested or reforested yearly worldwide, especially in zones limited by water availability, while in UE27, 100 million trees are planted yearly. The investment on plant establishment is commonly imbalanced with the resources devoted to monitoring and tending operations, resulting in frequent low survival rates, especially in areas suffering from drought. The main causes of failure, besides browsing damage, are drought and competing vegetation. The main current techniques against them imply high economic and environmental costs, with a massive use of fossil fuels, plastics or herbicides.
A group of 6 highly specialized European Small and Medium Enterprises (SMEs – Terrezu, TerraCottem Internacional, La Zeloise, EcoRub, DTC and Ceres) launched a joint project in order to develop new alternatives for increasing the success of tree planting projects, by developing innovative techniques meeting 5 requirements: cost-efficiency, sustained effect, versatility, environmental friendliness and consistent technical features.
This partnership of SMEs launched SUSTAFFOR project (Bridging effectiveness and sustainability in afforestation / reforestation in a climate change context: new technologies for improving soil features and plant performance), for what they contacted 4 Research & Technology Developers in order to evaluate the performance of novel techniques in laboratory and field trials: CTFC, EDMA (ES), CENTEXBEL (BE) and CNRS (FR).
The aim of SUSTAFFOR was to conceive, produce, develop and thoroughly evaluate (at laboratory and field level) novel techniques aiming at improving AF/RF projects from an environmental, technical and economic point of view, and to explore synergies between them. The novel techniques include:
- A new soil conditioner: a mix of products aiming at improving soil conditions, especially water retention capacity where roots grow during the first years, including hydro-absorbent polymers free of polyacrylamide, fertilizer & root growth precursors. This technique aims at mitigating the impact of drought in young plantations, being a one-time alternative to recurrent emergency irrigations.
- Four new groundcovers: these layers are installed in the soil around the tree stem, mitigating the negative effect of competing vegetation and soil water evaporation. The four models include three fully biodegradable versions, based on new biopolymers and on jute fibres treated with organic resin for enhanced durability. The fourth groundcover is a long-lasting (15 years) unit based on recycled rubber. These techniques are an alternative to recurrent and unsustainable weeding options, i.e. herbicide application and mechanical weeding, as well as to plastic mulching.
These techniques were tested in field and laboratory trials in order to ascertain their effect at tree, soil and micro-site level, and compared to reference techniques. Field testing consisted on eight trials distributed across a wide range of conditions (Semiarid, Mediterranean continental, Mediterranean humid, Montane) in NE Spain, representative of most conditions in Europe and the Mediterranean.
The new soil conditioner improved significantly tree performance in areas limited by poor and sandy soils (Semiarid and Montane), especially when limited by water deficit (Semiarid). However, in highly productive sites with rich soils the effect was negligible.
The new groundcovers showed an outstanding performance in terms of tree fitness and soil moisture compared to untreated trees, especially in the most productive sites (Mediterranean continental and humid). The results of these techniques were in general superior to those obtained by herbicide application, and were similar to commercially available plastic groundcovers.
For the moment, there are no major effects detected on the variables related to soil organic matter dynamics.
The new techniques proved to be a feasible alternative (both technically and economically) to current techniques applied against drought and competing vegetation in tree planting, bringing environmental benefits.
Project Context and Objectives:
1. The challenge of tree planting
Tree planting is a major challenge worldwide, mobilizing a vast amount of resources, with a wide range of objectives, often combined in the same space and time:
- productive: forest goods including timber, fruit, fuelwood, game, cork, non-timber forest products, etc.
- protective: especially soil (mitigation of wind and runoff erosion), water (less sediments, higher quality, promotion of infiltration and aquifer recharge) and biodiversity (habitat for flora and wildlife species).
- social: landscape, recreation, prevention of damages on crops or on human health linked to reduced erosion and improved water quality.
According to FAO Global Forest Resources Assessment 2010, an area of 12 million ha is reforested yearly worldwide, a large proportion of which corresponds to zones where primary production is limited by water availability (arid, semiarid and Mediterranean conditions – meaning more than 40% of Earth land surface). In the case of Europe, around 3 million ha of agricultural land only have been afforested in 1990 – 2010, apart from additional several thousand hectares corresponding to ecological restoration of degraded land, artificial regeneration of forests, gardening, landscape plantations (e.g. besides roads or infrastructures), etc. According to UNEP, around 100 million trees are planted yearly in UE27. The global estimation of the area suitable for restoration, where afforestation has a major role, is 2 billion hectares (Laestadius, 2011).
2. Tending operations in tree planting projects
These massive investments for plant establishment are commonly imbalanced with the resources devoted to monitoring and tending operations on the newly planted areas, resulting on frequent partial or total failure of these tree planting projects. The tending operations aim especially at mitigating the negative effect of two factors:
- Drought (especially in areas limited by water availability): the negative effect of drought can be exacerbated by factors including a light soil texture, high temperatures and wind. This event is hardly foreseeable and can occur at any moment and any site. In the framework of climate change, with an expected rise in temperatures and a more uneven distribution of the precipitation, especially in Mediterranean areas, drought events are expected to become increasingly severe.
- Competing vegetation (especially in medium to highly productive sites): because of their fast and vigorous growth, weeds can outcompete newly established trees and shrubs by impeding their access to water, nutrients and light. This unwanted vegetation also hide the planted trees, which pose a difficulty to the maintenance and monitoring activities.
Both negative factors are, besides wildlife damage, the main threats in our conditions, being particularly negative for newly established trees with an underdeveloped root system and thus incapable of reaching a large volume of soil.
The final effect of these two factors, either independently or combined, may range from slight growth reduction, higher sensitivity to pests and diseases, to the mass failure of the tree planting project, leading to major economic losses and social discouragement towards the potential restoration of the area.
3. Traditional versus new approaches of tending operations in tree planting
The traditional approach to tree planting, still applied in most sites in Europe, is to rely on corrective measures against drought and competing vegetation, based on repeated and often unsustainable techniques such as emergency irrigation, herbicide application or mechanical weeding. However, with the increasingly limited resources, the rise of labour costs and equipment and the growing social concern towards sustainability, these practices are more and more inapplicable. If the tree planting project was designed and implemented relaying on the mentioned repeated interventions, and they cannot be ultimately applied, the probability of success of the project is reduced dramatically. For example, Alloza et al (1999) found average success rate of tree planting projects as low as 30%, especially in areas suffering from drought. It is thus necessary to develop new approaches to tree planting, designing the project with the involvement of techniques meeting the following five requirements altogether:
a) Cost-effectiveness: the techniques must be effective against the negative impact of drought and competing vegetation, with a clear increase in tree performance compared to the non-application. This effect must come at the lowest cost possible to be applicable. The cost must refer to the whole cycle of the technique: acquisition, installation / application and disposal.
b) Sustained and cumulative synergic effect on plant fitness (survival and growth) over the first years of plantation, until tree establishment is successful (at least 4-5 years). The use of long-lasting preventive measures is prioritized by most managers of tree planting projects, as allowing a better planning of the investment.
c) Versatility: the technique must be valid in a wide range of climatic and soil conditions and for multiple purposes: any activity implying tree or shrub plantation, both individually and combined with other techniques.
d) Environmental friendliness: the social concern and the level of environmental impact of human activities are resulting in a legal framework more and more restrictive with regard to the techniques and materials that can be utilized. Thus, there is a growing need for sustainable techniques, considering the whole lifetime: raw materials, production, application/utilization and disposal. Some social and environmental requirements of growing importance are: avoidance of toxicity for soil, water and air, low visual impact, use of locally produced materials for reducing low carbon footprint, etc.
e) Well-known technical features: a commercial product should have well-known and features regarding composition, durability and degradability, as well as foreseeable performance, in order to ease its labeling and use prescription
4. Most common techniques applied to mitigate drought impact on tree planting projects
The main techniques aiming at reducing the negative impact of drought in tree planting projects in Europe are two:
- Special soil preparation, including water harvesting and micro-catchments. This technique pretends to modify micro-physiography to concentrate runoff, and/or to perform a deep soil preparation (up to 80 cm depth). This is a preventive measure with very variable level of cost and environmental impact depending on the particular technique an area.
- Artificial water application: depending on the context of the tree planting project (especially, the accessibility of the site) water can be applied with pre-installed drippers (easily accessible sites) or with water wagons. In both cases, the techniques imply high application costs, a massive investment of labour and a noticeable environmental impact.
As an alternative or complement to both types of techniques, the last years have witnessed the development of soil conditioners. This product is mixed with the soil at the planting pit to improve the physical (and often chemical) features at micro-site level, especially, water holding capacity. Apart from organic conditioners (peat, biochar, sawdust) and mineral conditioners (perlite, vermiculite, sand / clay, etc), synthetic options are being more and more utilized by managers. Synthetic soil conditioners include in its composition hydro-absorbent polymers, which are able to store large amounts of water keeping it available for the tree roots and reducing the losses from evaporation and percolation. The main advantages of soil conditioners in general, and synthetic ones in particular, include its simple application (one-time only, during tree planting), versatility and low dosage required. However, the synthetic versions have a drawback, which is the poor social perception of some of the polymers utilized, especially, polyacrylamide.
5. Most common techniques applied to mitigate competing vegetation impact on tree planting projects
The main techniques applied to control competing vegetation in tree planting projects are:
- Mechanical weeding: consisting on destroying competing vegetation with man-operated tools or machines (e.g. brush cutter) or with tractor-operated devices (plough, flail mower). Both cases involve the use of fossil fuels and the risk of damaging the trees (if applied close to the stem) or being ineffective (if applied far from the stem).
- Chemical weeding: application of herbicides to prevent the germination or to suppress competing vegetation. Because of the environmental damages, this technique is strongly regulated with regard to the products and doses that are applicable. Moreover, this practice raises a growing social concern, and its use is being progressively restricted in protected areas and public forests in many countries.
Apart from the mentioned limitations of these techniques, both options imply repeated applications, which are more frequent as the site is more productive. As a result of these limitations, in the last years a technique developed in agriculture is being progressively introduced to tree planting projects: the use of groundcovers. This technique consists on covering the soil besides a tree (or along a row of trees), for impeding the establishment or proliferation of competing vegetation near the stem. The groundcover (also known as “mulch”) has a triple effect: avoids the germination and install of competing vegetation, mitigates soil water evaporation and eases the finding of young seedlings for maintenance and monitoring purposes. There is a wide range of products that can be utilized for this purpose: organic waste or by-products from agricultural or forest operations (straw, chips, bark), stones and layers made of plastic, paper, textiles, cardboard or long-lasting materials. For the moment, the most common material is a thin plastic layer, because of its low retail price, but it has as main drawback the need to remove it from each tree at the end of its service life (5-6 years), which is an expensive intervention. As a result, in the last years new materials are being developed, especially, biodegradable options which allow avoiding the need for removing the groundcover, as well as long-lasting groundcovers which can be utilized in long-term tree planting purposes (e.g. gardening) or reutilized several times.
6. SMEs and RTDs partnerships: collaborating for developing improved solutions for tree planting
The state of the art described makes evident that there is a need for having innovative solutions for avoiding the negative effects of drought and competing vegetation with techniques that meet the five requirements described in the point 3. In this sense, both soil conditioners and biodegradable / long lasting groundcovers seem to be interesting lines to explore, both individually and combined: as the soil conditioners improve site features at micro-site level, it is expected that competing vegetation might also favour from this enhancement. Therefore, the combination of new generation synthetic soil conditioners and groundcovers may lead to a synergic manner to mitigate the negative effect of both drought and competing vegetation. This is the leading principle and the origin of Sustaffor project.
A group of specialized SMEs producing soil conditioners (Terracottem Internacional) and materials which can be utilised for groundcover fabrication (DTC, La Zeloise and EcoRub) were put in contact by two SMEs specialized in eco-innovative solutions for environmental engineering, forest restoration and landcaping: Terrezu and Ceres. This partnership launched SUSTAFFOR project (Bridging effectiveness and sustainability in afforestation / reforestation in a climate change context: new technologies for improving soil features and plant performance). In order to multiply the impact and interest of the new techniques to develop, they contacted several Research and Technology Developers (RTDs), with different functions:
- Forest Sciences Centre of Catalonia, to provide support in aspects such as technical requirements of the new techniques and the assessment of their performance in field conditions, considering a wide range of tree, soil and environmental parameters.
- Edma Innova, to support the settlement of monitoring equipment in the field trials
- CNRS- IC2MP - Environmental and Material Chemistry Institute of Poitiers, to provide a cutting-edge technology and analytic capacity to characterize the effects of the degradation of the innovative techniques in the soil.
- Centexbel, to provide know-how related to the fabrication routes of the groundcovers and to perform degradation tests.
This collaboration of SMEs and RTDs has resulted in the achievement and assessment of novel techniques, tested and characterized in detail, both individually and combined, and compared to reference techniques. The innovative techniques developed during the project are five:
- An innovative soil conditioner, including a new high-performance hydro-absorbent polymer free of acrylamide in an improved mixture of 20+ ingredients (TerraCottem Internacional).
- A 100% biodegradable framed groundcover made of a new biopolymer formulation, fused to a flexible bioplastic sheet (DTC).
- A 100% biodegradable semi-rigid groundcover, made of a new biopolymer formulation (DTC).
- A 100% biodegradable goundcover made of woven jute fibres treated with furan bio-based resin for increased durability (La Zeloise).
- A long-lasting (10-15 years) groundcover based on recycled rubber and anti-UV treated for enhanced durability (EcoRub).
6. Objectives of Sustaffor project
The main objective of SUSTAFFOR is to conceive, produce, develop and on-field validate novel techniques aiming at improving afforestation / reforestation projects from an environmental, technical and economic point of view, as well as to explore the synergies between them.
Moreover there are thematic objectives, described below:
Technical-scientific objectives
- To improve tree water status and soil water retention thanks to the soil conditioner
- To increase the durability and estimate the service life of novel mulching techniques
- To reduce overall service costs of weeding techniques
- To increase and quantify the positive effects on tree fitness, and the synergic effect of combining mulching and soil conditioning techniques
- To improve and quantify the positive effect of novel techniques on key soil physical and chemical features
- To reduce global AF/RF costs during the first 5 years
Commercial objectives
- Strengthen the market position of the participating SMEs
- Exploitation Intellectual Property Rights (IPR) of the novel techniques
- Raise awareness of managers and end-users on the technical and environmental benefits of soil conditioners and biodegradable or multiple-use mulching
Environmental-social objectives
- To use acrylamide-free polymers in soil conditioners
- To reduce the use of plastics, herbicides, water and fossil fuels consumption in the establishment and maintenance of AF/RF projects
Project Results:
The vast quantity of variables gathered and results obtained during the project makes necessary to organize them in a consistent manner. They will be presented below, organized as follows:
1. Description of the experimental design, field trials and variables monitored.
2. Main results for each variable.
3. Main results and conclusions for the different novel techniques developed in the project.
The results are described in general terms, and more detailed information can be found in the attached information and in the publications prepared during the project.
1. Novel techniques, experimental design and variables monitoring
This section describes the novel techniques developed during the project, the treatments considered, the experimental design of the field and laboratory trials and the whole set of variables studied.
1.1. Development and description of the innovative techniques
1.1.1. Novel acrylamide-free soil conditioner (TerraCottem Internacional)
Although it has been proven that the Terracottem soil-conditioner TCU® enhances drastically the growth of plants and has no negative ecological effects, there is still a concern in the market, since the material is partially based on polyacrylamide chemistry.
An intensive reformulation program was started to develop and alternative polyacrylamide-free soil conditioner that still retains or further improves the properties of the reference Terracottem TCU. After primary chemical analysis a dozen formulations were tested in fast bio-screening trials in green-houses to assess the performance as soil-conditioner.
Based on these results a final optimised formulation encoded TCUplus was selected for upscaling trials and supplied for the further afforestation field trials. This final product was produced in appropriate amounts for the planned Sustaffor field trials and after quality controls sent to the coordinator CTFC.
1.1.2. Novel full-plate biodegradable groundcover via injection moulding (DTC)
For the development of novel groundcover system a first route followed is by injection moulding technology. Instead of using petrochemical based polymers such as PP or PE, biopolymers were used. Several polymer types including PLA, PHA, starch-based and blends of them were evaluated, both for processability properties and intrinsic properties of the injection moulded parts including, flexibility, strength and impact resistance.
Finally a special designed biopolymer blend was defined for the final production trials offering the best performance both in processability and in properties.
A special mould was designed in order to produce in a single step a groundcover of 40 by 40 cm, specially adapted to facilitate installation. It was also possible to combine 4 groundcovers to create larger model of 80 by 80 cm.
1.1.3. Novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (DTC)
A support structure made of biopolymers was injection moulded directly on a biodegradable biopolymer film. Although the film part may have a lower durability than the injection moulded part, the advantages are that a lightweight and economic structure is obtained, that still can easily be installed and fixed to the ground due to the semi-rigid rim.
1.1.4. Novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (La Zeloise).
Groundcovers made of jute fibres are commercially available and can already be used as groundcover. However their durability especially in warm and humid environment is limited. As a result, La Zeloise has used a novel approach by applying a bioresin that acts as a preservative and extends the lifetime of the product. The bioresin formulation along with the application process required further optimisation to get optimal performance of the groundcover. Also the impact on mechanical properties and stiffness was examined and brought under control by selection of formulation, process methodology and applied concentration. Due to the raised stiffness of the fabric, the groundcovers are easier to handle during installation around the tree. The materials are not only fully biobased but offer as well a full biodegradability after an extended lifetime of about 3 to 5 years. The bioresin treated fabric show also improved properties against flammability.
Since production is performed in full width via roll to roll impregnation, drying, curing groundcovers can be produced in a flexible way in all varieties of sizes.
1.1.5. Novel long-lasting groundcover made of recycled rubber (EcoRub)
The use of recycled materials to build groundcovers can offer large ecological benefits. Ecorub produces a range of different articles based recycled rubber offering a second life to materials that normally will be burned or deposited.
Based on their technology, a rubber mat was created to be used as groundcover. The material is not biodegradable but instead it can be used for a long time (10-15 years). For the Sustaffor project a thickness of 1.5 mm was selected offering an appropriate balance in strength, weight, handling and installation possibilities, as avoiding the need for being removed at the end of its service life.
1.2. Techniques tested and experimental design.
The performance of these novel soil conditioners and groundcovers were tested in a range of eight outdoor field trials. In order to assess their performance, they were compared to reference techniques, i.e. those currently applied for the same purpose. Moreover, the different types of techniques were combined to conform a range of experimental treatments.
1.2.1. Techniques aiming at minimizing drought negative impact
The techniques aiming at minimizing drought negative impact on tree planting were, for seven of the field trials:
- The described novel soil conditioner (1.1.1) at the prescribed dose (40 g/tree). This technique is coded “TCU+40g” hereinafter.
- The described novel soil conditioner (1.1.1) at a lower dose (20 g/tree), coded “TCU+20g” hereinafter.
- The described novel soil conditioner (1.1.1) at a higher dose (80 g/tree), coded “TCU+80g” hereinafter.
- A reference commercial soil conditioner TerraCottem Universal at the prescribed dose (40 g/tree), coded “TCUStd40g” hereinafter.
- Control (no application of soil conditioner), coded “NoSC” hereinafter.
In the remaining field trial (numbered 4) involving trees mycorrhized with edible fungi, a different group of techniques were applied to mitigate drought negative effects:
- The described novel soil conditioner (1.1.1) at the prescribed dose (40 g/tree).
- A reference commercial soil conditioner consisting only on hydrogel (hydroabsorbent polymer alone) at a dose of 50 g/tree, coded “CommHydrogel” hereinafter.
- A reference commercial organic soil conditioner consisting on peat, at a dose of 360 g/tree, coded “CommPeat” hereinafter.
- Control (no application of soil conditioner).
1.2.2. Techniques aiming at minimizing competing vegetation negative impact
The techniques chosen were, for seven of the field trials, the following:
- The described novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (1.1.3) coded “BIOPOLYMER” hereinafter.
- The described novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (1.1.4) coded “JUTE” hereinafter.
- The described novel long-lasting groundcover made of recycled rubber (1.1.5) coded “RUBBER” hereinafter.
- A reference commercial biodegradable woven film, coded “CommBiofilm” hereinafter.
- A reference commercial plastic (polyethylene) film, treated anti-UV, coded “CommPE” hereinafter.
- A reference commercial herbicide (glyphosate) application, every spring, coded “CommHerbicide” hereinafter.
- Control (no application of any technique against competing vegetation), coded “NoWeeding” hereinafter.
Moreover, in two of the field trials (numbered 7 and 8), the described novel full-plate biodegradable groundcover via injection moulding (1.1.2) was also tested, coded FULLPLATE. The limitations in the production process made that no further units were available for the rest of the field trials.
In the remaining field trial, numbered 4, the assessed techniques aiming at controlling competing vegetation were the following:
- The described novel biodegradable groundcover consisting on a biopolymer frame fused to a commercially available biofilm (1.1.3).
- The described novel biodegradable groundcover made of woven jute fibres treated with bioresin for enhanced durability (1.1.4).
- The described novel long-lasting groundcover made of recycled rubber (1.1.5).
- A reference commercial plastic (polypropylene) woven mat, treated anti-UV, coded “CommPP” hereinafter.
- A reference commercial herbicide (glyphosate) application, every spring.
- A reference mechanical weeding (hoe) application, every spring, coded “CommMechanical” hereinafter.
- Control (no application of any technique against competing vegetation).
1.2.3. Experimental treatments
The experimental treatments are combinations of the different techniques utilized to control the negative impact of drought and of competing vegetation. The combinations are the following (see codes above):
For seven of the field trials:
- All the techniques applied to mitigate drought effects combined with CommPE
- All the techniques applied to control competing vegetation combined with TCU+40
- All the techniques applied to control competing vegetation combined with NoSC
In total, 17 treatments (19 in the case of field trials 7 and 8) were installed in each field trial. Each of these treatments was applied to 30 trees, distributed following a full random block design, with 6 blocks per field trial composed of 5 trees from each treatment.
In the case of field trial 4, the treatments were:
- All the techniques applied to mitigate drought effects combined with CommPP
- All the techniques applied to mitigate drought effects combined with NoWeeding
- All the techniques against competing vegetation combined with TCU+40
In total, 13 treatments were installed at 12 trees each. The treatments were organized following a full random block design, with 12 blocks composed of 1 tree from each treatment.
The total number of experimental trees was 3,846.
1.3. Field trials
The eight field trials were deployed in four strongly contrasting conditions located in northeast Spain, representative of most conditions in Europe and the Mediterranean:
1.3.1. Semiarid bioclimate with light soil (Field trials 1 and 2): located in Mequinenza municipality (Saragossa province), in conditions severely limited by water availability linked with poor precipitation regime (370 mm annual precipitation, 70 of which during summer), high temperatures (15ºC mean annual temperature, 30ºC mean temperature of the warmest month), a light soil (loamy-sandy texture) a steep slope (40-70%) and, in the case of field trial number 1, a south-facing aspect. These field trials, located in a forest area burnt in 2005, were planted with Aleppo pine (Pinus halepensis). Because of the poor productivity of the site, the techniques applied to control competing vegetation were 40x40 cm, and it was not necessary to apply the treatment CommHerbicide.
1.3.2. Mediterranean continental bioclimate with rich soil (Field trials 3 and 4): located in Solsona municipality (Lleida province), in conditions limited by slight to moderate summer drought. The site is very productive, located in two flat former agricultural fields on fertile soils, rich and with moderately heavy texture (loamy-clayish). Mean annual precipitation is 685 mm (185 of which during summer) and mean annual temperature is mild (12 ºC). These trials were planted with hybrid walnut (Juglans x intermedia) and holm oak (Quercus ilex) mycorrhized with black truffle (Tuber melanosporum). The techniques applied to control competing vegetation were 80x80 cm.
1.3.3. Mediterranean humid bioclimate with rich soil (Field trials 5 and 6): located in Banyoles municipality (Girona province), in very productive conditions slightly limited by punctual summer drought events. The field trials are located in two flat former agricultural fields on fertile soils, rich and with moderately heavy texture (loamy-silty). Mean annual precipitation is 870 mm (215 of which during summer) and mean annual temperature is warm (14 ºC). These trials were planted with hybrid walnut (Juglans x intermedia) and stone pine (Pinus pinea). The techniques applied to control competing vegetation were 80x80 cm.
1.3.4. Montane bioclimate with poor, light soil (Field trials 7 and 8): located in Fontanals de Cerdanya municipality (Girona province), in conditions limited by a light textured soil (loamy-sandy), low temperatures (7.5ºC mean annual temperature, 0ºC mean temperature of coldest month) and north aspect, and by a moderate slope (30% in average). Mean annual precipitation is 885 mm (270 of which during summer). These trials were planted with European ash (Fraxinus excelsior) and birch (Betula pendula). Because of the poor productivity of the site, the techniques applied to control competing vegetation were 40x40 cm, and it was not necessary to apply the treatment CommHerbicide.
1.4. Monitoring
The following variables have been monitored between April 2014 and October 2015, totalling 2 vegetative periods:
1.4.1. Tree related variables: the variables most related to tree performance were monitored:
1.4.1.a Survival and vegetative status: assessed by direct observation at the end of each vegetative period, for all trees.
1.4.1.b Tree aerial growth: basal diameter and height measured with digital calliper and measuring tape, respectively, at the moment of planting and at the end of each vegetative period, for all trees. Tree volume is calculated as a cone with the tree basal area and the height of the tree. Tree growth of a given year is obtained as the difference between the initial and the final volume.
1.4.1.c Tree biomass allocation: six trees per treatment were pulled up at the end of the first vegetative period for calculating the dry biomass of different tree organs: fine roots (< 2mm diameter), coarse roots (> 2mm diameter), stem, needles (in the case of pine). This work was done in field trials 1, 2 and 3.
1.4.1.d Tree water status: six randomly selected trees per treatment were monitored four times during summers of 2014 and 2015 for determining the level of water-related stress. The methods applied were Relative Water Content in the case of pine (percentage of water present on the needles with respect to saturated content) and leaf water potential (strength with which the tree retains the water in the leaf tissues), measured for broadleaved species with Schölander chamber). These variables were measured in field trials 1, 2, 3, 5 and 7.
1.4.1.e Tree nutrient status: six randomly selected trees per treatment were monitored two times during summers of 2014 and 2015 for assessing their nutrient status. The method utilized was a SPAD-meter, a proxy of the chlorophyll content, and thus an indication of the nitrogen availability in the trees. This variable was measured in field trials 3, 4, 5 and 7.
1.4.2. (Micro-)environmental variables: the most relevant variables occurring at (micro-)site level affecting tree performance have been assessed.
1.4.2.a Soil moisture: measured in three trees per treatment in each field trial, seven times per year, between spring and autumn, at two different depths: 0-20 cm i 20-40 cm. The method has been a TDR probe inserted in pre-installed tecanate tubes. This variable was measured in field trials 1, 2, 3, 4, 5 and 7.
1.4.2.b Soil temperature: measured in a continuous basis in three trees per weeding treatment, through thermometers with built-in dataloggers, installed at two different depths: 5 cm and 15 cm. This variable was measured in field trials 1, 2, 3, 4, 5 and 7.
1.4.2.c Weather: a network of meteorological stations were installed in field trials 1, 2, 3, 5 and 7. These stations made a continuous recording of the most important weather variables: temperature, air humidity, precipitation, wind speed and direction, total radiation and UV radiation.
1.5. Soil variables
The most relevant variables related to soil organic matter dynamics were monitored in order to determine how they were affected by the different experimental treatments.
Although it was initially foreseen to analyse also total nitrogen, extractable ammonium, extractable nitrate and extractable phosphorus it was finally discarded in light of poor expectations of detecting relevant changes. Instead the study focused on:
1.5.1. Soil organic carbon: it was measured as an indicator of soil microbial activity. As a result of the (expected) increase in soil water retention and probably also changes in soil thermal regime due to the application of soil conditioners and/or groundcovers, we may expect an increase in soil microbial activity. This should result in an acceleration of soil organic matter decomposition, owing to the saprophyte regime of most soil biota. We looked for differences in soil organic carbon associated to either the presence of soil conditioner or the different groundcovers; a consistently lower value obtained for controls would mean that decomposition is enhanced. Organic carbon was analysed by dichromate oxidation, following the modified Mebius’ method (Nelson & Sommers, 1996).
1.5.2. Biochemical fractionation of soil organic matter: the aim was to detect changes in the structure of the soil organic matter stock. Since the decomposability of soil organic matter is the result of such a structure, these changes should precede the decomposition itself. The acid hydrolysis procedure of Rovira et al. (2012) was applied. By this method soil organic matter in ground soil samples is submitted to three consecutive extractions: (i) with hot K2SO4 0.5 M solution (water-soluble fraction, WS); (ii) with hot 2.5 M H2SO4 (labile pool 1, LP 1); and (iii) with cold 13M H2SO4, then diluted to 1M and boiled for 3 h (labile pool 2, LP 2). The unhydrolyzed residue is taken as the recalcitrant fraction. The liquid extracts and hydrolysates were analyzed for carbohydrates and phenolics.
The method is based upon standard methods to quantify polysaccharides in plants. The second hydrolysate (LP 2) matches the operational definition of cellulose, and therefore the ratio LP2 / total equals to the cellulose to total carbohydrates ratio. It has been shown that in soil samples this ratio decreases with decomposition. High values for this ratio may be interpreted as signs of abundance of fresh plant-derived materials.
1.5.3. Detection of specific organic compounds in the soil organic matter, as indicators of the degree of microbial reworking, and therefore of an accelerated or retarded biochemical evolution. Soil samples were subject to thermochemolysis with TMAH (tetramethylammonium hydroxide) in the presence of methanol, under N2 atmosphere at 450ºC. This treatment breaks polymers onto their monomeric composers, which are methylated and removed by a N2 stream. The released compounds are collected in cold (0 ºC) trichloromethane, concentrated and transferred to a vial, dried and redissolved in dichloromethane, then injected into a Hewlett-Packard gas chromatograph-mass spectrometer system. Identification of compounds was done from the mass spectra by comparison with published spectra and own data.
Data analysis focused on the detection and quantification of several groups of substances: fatty acids, sugars, and phenolics. For all these substances, there are several indices useful for evaluating the degree of microbial reworking and biochemical evolution.
The sampling was performed in field trials 1, 2, 3, 5 and 7, organized in three campaigns: March 2014, prior to planting (initial soil features, Sampling 0), October 2014 (after 6 months, Sampling 1) and June 2015 (after 14 months, Sampling 2). In each campaign, six samples were collected from each treatment and field trial, at two different soil depths: 0-10 cm and 10-20 cm. These six samples were finally grouped in three composite samples, each made by pooling two of them, chosen randomly. In total there are three composite samples per treatment and depth.
1.4. Groundcover durability / degradability study
Standardised mechanical tests are performed for the different groundcovers, to characterize their properties and how they are modified over time: tenacity, modulus at break and elongation. They are measured on a drawbench on a strip of woven textile, foil or plastic or rubber plate, according the respective standards: ISO 527 for the rubber and plastic plates (standard punched tensile bars; width 10 mm), ISO 13934 for the textiles and foils (test specimen width 25 mm).
These tests were applied to groundcover samples subjected to both artificial and real weathering:
- Artificial weathering: samples were put in Q-UV test chambers according to the standard ISO 4892-3. Materials were subjected to UV-A and/or UV-B illumination, according to the expected durability performance. Rubber or thick plastic plates are usually tested using the more aggressive UV-B light, in order to reduce treatment time to observe some degradation effects.
- Weathering in field conditions: ten samples from each groundcover were installed in April 2014 in areas annex to the field trials 1, 5 and 7. About 6, 12 and 18 months after installation samples were retrieved from the testing fields and the mentioned mechanical properties were analysed to evaluate the degradation.
2. Main results related to tree performance variables
2.1. Tree survival and vegetative status, at the end of 2015 vegetative period:
2.1.1. Field trial 1: 77% alive & healthy, 2% alive with vegetative problems; 21% dead
The trees with soil conditioner resulted in higher survival rates (77%) than those without it (63%). The survival rate was increased with soil conditioner dosage 71% for TCU+20g, 75% for TCU+40g and 79% for TCU+80g.
Likewise, those with any technique to control competing vegetation showed higher survival rates (80% in average) than those without (66%). JUTE and RUBBER groundcovers achieved the highest survival rates (86% and 87%, respectively), while CommPE led to poorest survival (70%) among the different groundcovers.
2.1.2. Field trial 2: 87% alive & healthy, 0% alive with vegetative problems; 12% dead
The use of soil conditioner led to higher survival rates (92%) than in the case of not using this technique (85%). There was not a clear trend in survival rates depending on the dosage.
However, trees with any technique to control competing vegetation showed slightly lower survival rates (84% in average) than those without them (92%). BIOPOLYMER groundcover led to highest survival rate (90%) among the different groundcovers, while RUBBER (77%) was the only one with survival rates below 80%.
2.1.3. Field trial 3: 87% alive & healthy, 9% alive with vegetative problems; 4% dead
There were no major effects of the application of soil conditioner or of techniques aiming at mitigating the negative effects of competing vegetation.
2.1.4. Field trial 4: 86% alive & healthy, 9% alive with vegetative problems; 6% dead
The use of soil conditioners slightly increased survival rates (95%) compared to NoSC (92%). The different soil conditioning treatments had very different results between them: CommHydrogel led to survival rates of 86%, while both TCU+40g and CommPeat resulted in 96% survival rates.
The use of techniques to control competing vegetation was positive to survival rate, compared to not using them (98% vs 88%). Among them, CommMechanical provided the poorest results (88% survival), while all the others avoided mortality.
2.1.5. Field trial 5: 92% alive & healthy, 8% alive with vegetative problems; 0% dead
The lack of mortality in these field trials makes impossible to compare among treatments.
2.1.6. Field trial 6: 89% alive & healthy, 5% alive with vegetative problems; 7% dead
Soil conditioners did not affect survival rates in this field trial. Similarly, the use of techniques against competing vegetation did not have a decisive impact on survival rates compared to untreated trees. However, the different techniques led to contrasting results: BIOPOLYMER groundcover resulted in full survival (100%), while CommHerbicide and CommBiofilm led to poorest survival results (90% and 83%, respectively).
2.1.7. Field trial 7: 23% alive & healthy, 71% alive with vegetative problems; 7% dead
Most of vegetative problems were caused by the wildlife, despite the perimetric fence installed in the site. The survival rate is very high in any case, averaging 93%.
The use of soil conditioner was positive to survival rate, which was increased from 90% to 95% with the use of this technique. The effect of the different doses were not remarkable.
There was no effect of applying techniques to control competing vegetation on the survival rates, either compared with untreated trees or compared among them.
2.1.8. Field trial 8: 72% alive & healthy, 20% alive with vegetative problems; 8% dead
Like in the case of field trial 7, approximately the half of vegetative problems were caused by wildlife damages.
The use of soil conditioner increased survival rate from 91% (NoSC) to 96%. There was a positive effect with increased dose: survival rates were 90, 97% and 100% for doses of 20, 40 and 80 g/tree, respectively.
Finally, the use of techniques to mitigate competing vegetation impact did not have a major effect on tree survival. However, the different weeding techniques led to different survival rates, with RUBBER, BIOPOLYMER and FULLPLATE leading to highest values (97%, 95% and 94%, respectively) and CommPE, CommBiofilm and JUTE leading to lowest survival rates (88%, 88% and 90%, respectively.
2.2. Tree aerial growth
As the dataset is large and complex to describe as text, we will provide, for each field trial, the significant differences between treatments with regard to tree aerial volume growth. With that aim, we will show the grouping of treatments according to the Duncan test. Different letters (a, b, c) indicate that the treatments are significantly different (p<0.05) being “a” the treatment with the lowest value of growth and “b”, “c”, etc, higher values of growth.
2.2.1. Field trial 1:
The soil conditioner increased tree growth compared to NoSC in both 2014 and 2015, with higher growth rates as the dose is increased: NoSC (“a” in 2014, “a” in 2015); TCUStd40g and TCU+20 g (b, ab) and finally TCU+40g and TCU+80 g (b, b).
Similarly, treatments to control competing vegetation in general also increased tree growth: NoWeeding (a, a) in front of CommPE (ab, b), JUTE (b, ab) and BIOPOLYMER (b, b).
2.2.2. Field trial 2:
The positive effect of soil conditioner on tree growth was noticeable and consistent, with all formulations and doses providing significantly higher rates than NoSC in both 2014 and 2015. There were no significant differences between the different products and doses.
In the case of the treatments to control competing vegetation, the gain in tree growth was less remarkable, although present for most techniques: NoWeeding (a, ab) led to the worst results, not improved by BIOPOLYMER (abc, a), CommPE (abc, bc) or RUBBER (ab, bc). However, CommBiofilm (bc, bc) and especially JUTE (c, c) did improved notable the results of NoWeeding.
2.2.3. Field trial 3:
The soil conditioner did not have a significant effect of tree growth at this field trial.
However, the techniques to control competing vegetation had a remarkably positive effect: all the techniques had superior aerial growth results than NoWeeding in both 2014 and 2015, with the only exception of CommBiofilm in 2015, which led not statistically higher growth rate than Noweeding.
2.2.4. Field trial 4:
The soil conditioner did not have a significant effect of tree growth at this field trial.
Some of the techniques to control competing vegetation improved the results of NoWeeding (a, a): CommPP in 2015 (ab, b), BIOPOLYMER in 2014 (b, ab) and RUBBER both years (b, b).
2.2.5. Field trial 5:
The soil conditioner did not have a significant effect of tree growth at this field trial. However, the techniques aimed at controlling competing vegetation had a remarkable effect: all of them increased tree growth both years (b, b) compared to NoWeeding (a, a), with the only exception of CommBiofilm in 2015 (b, ab).
2.2.6. Field trial 6:
Like in the previous field trial, the soil conditioner did not have a significant effect of tree growth, while the techniques to control competing vegetation led in general to results superior to NoWeeding (a, a), and with noticeable differences between them: CommHerbicide (ab, bc), CommBiofilm (bc, ab), BIOPOLYMER and RUBBER (c, bcd), JUTE (c, cd) and CommPE (c, d).
2.2.7. Field trial 7:
The soil conditioner significantly increased tree growth in 2014, but not in 2015. The growth of trees with NoSC (a) was not significantly worse than TCU+20g (ab), but the other doses and formulations showed better results: TCUstd40g (bc) and TCU+40g and TCU+80g (c).
On the contrary, the different treatments to control competing vegetation did not have an influence on tree aerial growth.
2.2.8. Field trial 8:
Soil conditioning did not have an effect on tree aerial growth, unlike some techniques against competing vegetation: NoWeeding (ab, a) resulted in lower tree growth rates than CommPE (c, b) and than BIOPOLYMER in 2014 (c, ab).
2.3. Tree biomass allocation
Like in the case of tree aerial growth, only the significant differences between treatments will be shown. As mentioned before, this variable was only measured in field trials 1, 2 and 3.
2.3.1. Field trial 1
Root biomass and Total biomass were increased thank to the soil conditioner when applied in doses of 40 g/tree (in both formulations) and 80 g/tree. The lower dose (20 g/tree) did not lead to significantly higher root biomass (ab) than NoSC (a), in both variables.
In the case of the techniques to control competing vegetation, BIOPOLYMER also led to higher root biomass than NoSC.
2.3.2. Field trial 2
Neither the soil conditioners nor the techniques to control competing vegetation had a decisive effect on biomass allocation in this field trial.
2.3.3. Field trial 3
The soil conditioner did not have an influence on biomass allocation. However, the use of techniques to control competing vegetation led to gains in fine, coarse and total root biomass, as well as in aerial and total tree biomass. Compared to NoWeeding, JUTE, BIOPOLYMER and RUBBER increased the results of all the mentioned components, without major differences between these treatments. These treatments also provided higher results than CommHerbi for fine, coarse and total root biomass and for total tree biomass, and than CommPE for fine and total root biomass. CommBiofilm increased coarse and total root biomass, as well as total tree biomass, compared to NoWeeding.
2.4. Tree water status
As mentioned above, this variable was measured in field trials 1, 2, 3, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment.
In the field trial 1, all types and dosages of soil conditioner led to significantly higher needle relative water content than NoSC, although no remarkable differences were found between the different soil conditioner applications. The different techniques against to control competing vegetation did not have a decisive effect on tree water status.
In the field trial 3, both JUTE and CommBiofilm (c) increased the results of tree water status compared to CommHerbicide and CommPE (a) and to NoWeeding and BIOPOLYMER (ab).
In the other field trials where tree water status was monitored the different treatments did not have a decisive influence.
2.5. Tree nutrient status
As mentioned above, this variable was measured in field trials 1, 2, 3, 4, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment. The significant differences found between treatments did not follow a consistent trend in any of the field trials.
3. Main results related to (micro-)environmental variables
3.1. Soil moisture
As mentioned above, this variable was measured in field trials 1, 2, 3, 4, 5 and 7. The analysis of the data refers to the whole dataset for each field trial, and is not done for each measuring moment.
The only case where significant differences between treatments were found were:
- Field trial 1, 0-20 cm depth: BIOPOLYMER (bc), JUTE and RUBBER (c) increased soil moisture at this depth, compared to NoWeeding (a). CommPE (abc) and CommBiofim (ab) led to intermediate results. Likewise, in 20-40 cm depth, CommPlastic (b) led to higher soil moisture than NoWeeding, CommBiofilm, BIOPOLYMER and JUTE (a).
- Field trial 2, 20-40 cm depth: all the techniques to control competing vegetation increased soil moisture compared to NoWeeding (a). CommPE and RUBBER (c) led to higher soil moisture at this depth than CommBiofilm, BIOPOLYMER and JUTE (b).
- Field trial 5, 20-40 cm depth: BIOPOLYMER (b) resulted in higher soil moisture than NoWeeding, RUBBER and JUTE (a).
- Field trial 7, 0-20 cm depth and 20-40 cm depth: BIOPOLYMER resulted, in both cases, to higher soil moisture than CommBiofilm.
4. Main results related to soils features
4.1. Soil organic carbon
The average values for total organic carbon in the different field trials ranged from 1.02 to 2.07%. Values were usually slightly lower as depth increased. Even when in some cases (Field trial 7) the values of sampling 2 were consistently lower than in sampling 1, usually differences between the two samplings were too small and not statistically significant. Thus it is not possible to state a true decrease in organic carbon content, and therefore we cannot reliably quantify soil organic matter decomposition.
The soil conditioner did not have a significant effect on soil organic carbon content in any of the samplings or field trials.
In the case of techniques applied to control competing vegetation, few differences were found: Field trial 1, sampling 2, all depths; Field trial 3, sampling 2, 10-20 cm depth and Field trial 5, sampling 2, 0-10 cm depth. Often, the organic carbon content was lowest under JUTE. These effects, however, were not consistent enough to state that a given type of mulch results in the highest enhancement of microbial activity.
Table 1. Organic carbon content (% w/w). Average values for different sites, at two depths, and two samplings. The asterisk (*) indicates that significant differences were found linked to the technique for controlling competing vegetation.
0-10 cm depth 10-20 cm depth
Field trial Sampling 1 Sampling 2 Sampling 1 Sampling 2
Field trial 1 1.16 ± 0.34 1.02 ± 0.33 * 0.94 ± 0.35 0.95 ± 0.33 *
Field trial 2 1.50 ± 0.51 1.38 ± 0.38 1.45 ± 0.49 * 1.27 ± 0.45
Field trial 3 1.49 ± 0.13 1.62 ± 0.13 1.16 ± 0.10 1.42 ± 0.13 *
Field trial 5 1.51 ± 0.11 1.46 ± 0.18 * 1.23 ± 0.09 1.31 ± 0.20
Field trial 7 1.89 ± 0.56 2.07 ± 0.68 1.42 ± 0.62 1.78 ± 0.60
Since the pits were maintained mostly free of any input of organic matter, we expected a decrease in SOM, because SOM decomposition was the main (not to say the unique) process occurring in the plantation pits. The fact that no consistent decrease between samplings 1 and 2 was detected (Table 1) suggests that the within-plot spatial variability in SOM content hampered the detection of such a decrease. However it suggests also that the decomposition rate of SOM in the experimental plots is low enough to be confident that no substantial losses have to be expected as a consequence of the establishment of the plantation, a problem observed in many sites.
4.2. Biochemical fractionation of soil organic matter
4.2.1. Carbohydrates:
The relationship between carbohydrate content and total organic matter (measured by organic carbon) was highly variable, and strongly site-dependent (Table 2). Thus, the correlation between organic carbon content and relative richness in carbohydrates (in either WS, LP1 or LP2 pools; see 1.5.2 for a description of these fractions) was either positive or negative, depending on site and position within the soil profile.
Table 2. Correlation index (r) between total organic carbon (in %) and carbohydrate content (mg sugar C per g organic carbon).
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 10-20 cm 0.241 ns 0.358 * – 0.554 ***
2 10-20 cm 0.445 ** 0.215 ns – 0.498 **
3 10-20 cm 0.207 ns – 0.055 ns – 0.319 *
5 10-20 cm 0.063 ns 0.014 ns – 0.236 ns
7 10-20 cm – 0.344 * – –
1 0-10 cm – 0.086 ns – 0.127 ns – 0.398 *
2 0-10 cm 0.370 * – 0.622 *** – 0.008 ns
3 0-10 cm – 0.156 ns 0.124 ns – 0.301 †
5 0-10 cm – 0.087 ns 0.220 ns – 0.208 ns
7 0-10 cm – 0.291 † – –
The most consistent result was a negative relationship of total organic carbon content with the abundance of carbohydrates in LP2, the cellulosic ones. The lower the soil organic matter content, the higher the relative proportion of cellulose. This relationship was consistently negative, albeit it reached significance only in four cases out of eight tested.
For other indicators of carbohydrate abundance, either the sign was inconsistent, or reached significance in less than half the cases; thus they are not useful to detect trends in soil organic matter evolution. This is reflected further in the amounts of extracted carbohydrates, for which we did not detect any significant effect of any treatment.
The LP2 / total carbohydrates ratio (i.e. cellulose to total carbohydrates), an indicator of the richness of fresh plant-derived materials, ranged from about 3.5 % in Field trial 5 at 0-10 cm depth to about 25 % in Field trial 2, 10-20 cm depth. Thus the range of values (= the range in the degree of biochemical evolution of soil organic matter) is quite considerable. Values usually increased with depth: at 10-20 depth soil organic matter is more fresh, less evolved than at soil surface, obviously owing to the input of fresh roots. Again, no consistent effect of the technique against competing vegetation on this ratio was detected. As to the effect of soil conditioner, it was not detected in any case.
4.2.2. Phenolics:
The abundance of phenolics in LP1 is the most promising indicator of biochemical changes in soil (Table 3). The relationship with organic carbon content is consistently negative and always highly significant: the higher the organic carbon content, the lower the relative abundance of phenolics in this fraction. Sometimes the relationship is very high, particularly in semiarid field trials (1 and 2).
Table 3. Correlation index (r) between total organic carbon (in %) and the ratio of phenolics to total carbon (mg phenolic carbon per g of total organic carbon).
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 0-10 cm 0.051 ns – 0.748 *** – 0.184 ns
2 0-10 cm 0.281 ns – 0.795 *** – 0.593 ***
3 0-10 cm 0.392 ** – 0.414 ** – 0.099 ns
5 0-10 cm 0.017 ns – 0.422 ** – 0.001 ns
7 0-10 cm – 0.290 † – –
1 10-20 cm – 0.428 ** – 0.704 *** – 0.218 ns
2 10-20 cm 0.371 * – 0.708 *** – 0.575 ***
3 10-20 cm 0.043 ns – 0.710 *** – 0.179 ns
5 10-20 cm – 0.168 ns – 0.450 ** 0.191 ns
7 10-20 cm – 0.294 † – –
For other fractions the relationship is less clear (LP 2), or inconsistent (WS). In the hot-water extract the sign of the relationship was inconsistent (either positive or negative), thus not useful as indicator of biochemical changes.
The amounts of phenolics in the first hydrolysate (LP1), given in mg of phenolic carbon per gram of total organic carbon, ranged from 87 (Field trial 1, 0-10 cm) to 270 (Field trial 3, 10-20 cm). In the other extracts values were lower: usually less than 100 in LP 2, and less than 5 mg in WP. Differences associated to the treatment against competing vegetation were detected in some cases (e.g. Field trial 5 for the WS pool and LP 1, Field trial 2 for WS and LP 2, etc). In contrast, the addition of soil conditioners had no detectable effects.
4.2.3. Carbohydrate / Phenolic carbon ratio
The ratio between carbohydrate and phenolic carbon in the several labile pools (WS, LP1 and LP2) may serve as a complementary indicator for biochemical changes during decomposition. This index shows the proportion in these pools between easily decomposable substrates (in particular, carbohydrates) and substrates resistant to decomposition (phenolics as the most representative).
Table 4. Correlation index (r) between total organic carbon (in %) and the sugar carbon / phenolic carbon ratio.
Field trial Depth Fraction: WS Fraction: LP 1 Fraction: LP 2
1 0-10 cm – 0.116 ns 0.642 *** – 0.585 ***
2 0-10 cm 0.432 ** 0.765 *** – 0.329 †
3 0-10 cm – 0.166 ns 0.174 ns – 0.067 ns
5 0-10 cm 0.026 ns 0.205 ns – 0.101 ns
7 0-10 cm 0.216 ns – –
1 10-20 cm – 0.295 † 0.711 *** – 0.375 *
2 10-20 cm – 0.162 ns – 0.264 ns 0.291 †
3 10-20 cm –0.217 ns 0.362 * – 0.243 ns
5 10-20 cm 0.167 ns 0.296 † – 0.154 ns
7 10-20 cm 0.033 ns – –
The carbohydrate carbon / phenolic carbon varies depending on the pool. It is lowest in LP 2 (cellulosic hydrolysate), in which it ranges from about 0.1 (in Field trial 1) to almost 0.4 (in Field trial 3). The ratio usually increases with depth. In LP 1 the ratio ranges around 1-1.5 but differences between plots are noteworthy (e.g. values are unusually low for the field trial 3, < 0.5). Finally values are highest for the WS extract, the most easily decomposable pool, in which may be as high as 18 (Field trial 1).
The carbohydrate C / phenolic C ratio was never significantly affected by the application of soil conditioner. However it was sometimes significantly affected by the treatment against competing vegetation.
The relationship of this ratio with total organic carbon is almost always positive, and often significant (Table 4). This ratio is meant to reflect the biochemical quality of the main easily extractable fraction of soil organic matter, hence its quality as a substrate for soil microbial activity. The overall positive relationship with total organic carbon implies that the biochemical quality of this extractable pool will decrease as soil organic matter decomposes.
The biochemical quality of the second hydrolysate follows the opposite path; it is expected to increase with soil organic matter decomposition (negative relationship in most cases). However the number of significant correlations is lower, and therefore is less useful as indicator of biochemical change. Finally, the behaviour of the carbohydrate / phenolic carbon ratio in the water-soluble compartment seems largely affected by site.
4.2.4. Biochemical fractionation of soil organic matter: an overall view
Several of the studied parameters are good indicators of biochemical changes related to soil organic matter decomposition, and in spite of the short time of our experiment (less than two years of effective time) contrasted trends related to weeding treatments were already detected. We must expect that further soil samplings (foreseen in upcoming years) will allow for a more exhaustive description about how these changes affect soil biochemistry on the medium term.
A main result of our analyses is that the behaviour of many of the studied parameters depends on the site. The behaviour of the sugar / phenolics ratio for the WS pool, for instance, is not unique; the relative abundance of phenolics in WS pool also behaves differently from one site to another. Nevertheless, some of the studied parameters behave in a consistently similar way everywhere. The most clear is the abundance of phenolic compounds in LP 1, apparently the most promising indicator of biochemical changes with decomposition obtained in the biochemical fractionation protocole we applied.
In contrast, the addition of soil conditioner does not apparently result in biochemical changes in soil organic matter, relative to the control pits without any conditioner. This was somewhat unexpected, for this soil conditioner involves organic components which may serve as carbon source for the soil microflora (fungi and bacteria), and thus should have affected soil biochemistry somehow. The lack of any significant difference with the corresponding controls suggests that the expectable effects on the microbial activity of the soil conditioner are restricted to the very place where the conditioner was applied, i.e. the interface between the seedling root system and the surrounding soil.
4.3. Detection of specific compounds - Biochemical evolution of soil samples: study through TMAH-GC-MS
The thermochemolysis with tetramethylammonium hydroxyde, coupled with gas chromatography and mass spectrometry, was chosen as a technique for a global characterization of the soil samples, owing to the very high number of samples to be studied. This technique gives a global panoramic view about the chemical composition of the soil organic matter, and through the use of specific indicators, allows for a comparative evaluation of its biochemical evolution.
4.3.1. Fatty acids (FA) signature
Whereas plants produce FAs of all lengths, microbes produce virtually only short-chain FAs (< 20 carbons). Thus the ratio short to total FAs is an indicator of biochemical evolution of soil organic matter, more specifically the degree of microbial reworking.
In our soils, FA signatures are very high: 0.94 (Field trial 5), or 0.93 (Field trial 3). I.e. the very most of fatty acids (almost 95%) are short-chained. This points to a highly evolved lipidic pool, dominated by microbial-derived products. Whereas in Field trial 5 we did not detect any effect of sampling, in Field trial 3 the FA signature clearly increased with time: the setup of the experiment in Field trial 3 apparently accelerated this biochemical evolution. The FA signature was not affected by any treatment whatsoever.
4.3.2 Carbohydrate signature
While plants produce many structural pentoses, microbes produce very small amounts of them. The proportion between hexoses and pentoses (galactose + mannose ) / (arabinose + xylose) is a measure of the persistence of relatively undegraded, plant-derived tissue structures.
Values obtained in the soil samples of our experiment ranged between 16.8 and 2.3. They were highly variable, thus, which is not so strange taking into account that the presence of recently dead roots in a given soil sample may push this ratio to high values. Some effect of mulch type may be detected sometimes (e.g. in Field trial 5 in the first sampling, in the absence of soil conditioner); but the lack of consistency of these differences suggest that these effects were spurious. When considered all data altogether, no significant difference due to any treatment was detected. In Field trial 3, a significant effect of time was detected: the carbohydrate signature significantly decreased from the first to the second sampling.
4.3.3 Ratio ramified FAs / long-chain FAs
Ramified fatty acids are produced only by microbes. On the other hand, long-chain FAs (> 20 C) are produced only by plants. Thus the ratio between both may be a very sensitive indicator of biochemical evolution: the higher the ratio, the higher the degree of microbial reworking.
In our samples, the ratio ranges from about 0.9 (lowest value observed in Field trial 3) to 5.1 (highest value observed, in Field trial 5). No consistent effect of any treatment was observed. However the effect of sampling was clear and significant; the ratio increases with time at all sites, which indicates an active microbial reworking.
4.3.4 Phenolic compounds indicators
Most phenolic compounds in soil organic matter originate from lignin, the main polyphenolic polymer in plants. The biodegradation of lignin involves its depolymerization, but also oxidative processes by which their phenolic monomers are transformed: the aldehyde forms are oxidized to acidic forms. Within a given family of phenolic compounds (guaiacyl, syringyl), an increase in the acidic / aldehyde ratio is to be expected during lignin degradation.
No such an increase was observed for the guaiacyl phenolics; for siringyl phenolics, instead, a clear decrease was observed in Field trials 5. Thus apparently the degree of lignin oxidation decreased there: this is a surprising result, to be confirmed in future samplings. Alternatively, it could be due to the release into the soil of dead tissues, root-derived, rich in fresh and relatively undecomposed lignin.
4.3.5. Overall view
We detected signs of biochemical evolution with time in our samples. Overall such a detection shows how TMAH-GC-MS technique is more sensitive than the biochemical fractionation for the detection of microbial-driven evolution of soil organic matter, even when (as shown previously) the variability in soil organic matter content hampers the direct detection of organic matter mineralization.
The lack of any significant effect of neither soil conditioner presence nor groundcover type on the biochemical composition of SOM as studied by TMAH-GC-MS, however, suggests that, at least apparently, the differences in water availability and/or thermal regime in soil originated by the several groundcover / weeding techniques types do not generate contrasting paths in the biochemical evolution of soil organic matter, at least in the term studied in this project (< 2 years of effective study). We cannot discard that in future samplings more relevant differences between treatments could be observed.
4.4. Environmental implications
The lack of strong, significant differences in the biochemical features of soil organic matter relative to the controls indicates that neither the tested weeding techniques nor the soil conditioner application release into the soil organic matter any deleterious compound in detectable amounts. The natural soil biochemistry seems not affected, leaving aside a (probable, to be confirmed in future samplings) acceleration of SOM decomposition due to the increased water availability.
In fact, a main observation in the TMAH-GC-MS study was the lack of any detectable signal of extraneous compounds which could be attributed to any plastic or synthetic material used in the groundcovers or in the soil conditioner. These components do not penetrate into the soil to a detectable level: if present, they are retained by the groundcover itself, or – in the case of compounds derived from the soil conditioner – they are restricted to the very perimeter of the seedling root system.
This observation has obvious implications relative to the safety of the applied treatments. No potentially toxic compounds have been detected in soil organic matter, during these two years of the SUSTAFFOR project.
5. Main results related to groundcover durability / degradability study
5.1. Degradation of the full plate biodegradable groundcover (DTC)
5.1.1. Artificial weathering
Since thicker materials were tested the more aggressive QUV-B illumination (shorter wavelength, more aggressive UV light) was chosen. Tests were performed up to 2000 hours.
A first observation is that there is a drastic reduction of the strain percentage after a first period in the Q-UV chamber. This reduction is not due to a real degradation effect but is due to a (re)crystallisation process. Immediately after the production the bioplastic largely remains amorphous but as function of time and especially at raised temperatures the polymer will crystallise. This results in a reduction of strain; the material becomes stiffer and somewhat more brittle. Since flexibility is most important during installation the increased stiffness will be of limited importance.
A second observation is that due to the very aggressive UV-B light, also a severe reduction in tenacity is observed. The material retains ± 30% of its original strength after 2000 hours in the QUV-B test. Still the product keeps its full integrity and therefore its functional potential.
5.1.2. Weathering in field conditions
Similar observations are made for the strain at break during field weathering tests. After the first sampling (6 months after installation) a sharp drop in percentage of strain is observed again and can be assigned to the recrystallization of the polymer. This has however no real effect on the performance of the material.
In contrast to the artificial weathering under QUV-B conditions, it is observed that the tenacity properties are hardly reduced during the field tests. Only a minor reduction in tenacity is observed after 18 months in the fields. Via extrapolation it is to be expected that the effective lifetime of these groundcovers will probably be above 5 years certainly if only degradation by light is taken into account. Only a time dependent important increase in microbiological attack could speed up the degradation. After 18 months in the field, there is no proof for such in infestation found yet. The differences observed between climate zones are limited and not statistically relevant.
So it is concluded that the injection moulded bioplate groundcover, resist degradation under real weathering conditions very well and it is likely that the material will retain its functionality up to 5 years or even more.
5.2. Degradation of the groundcover made of a biofilm with injection moulded rim (DTC)
The rim material is similar to the one used for the bioplate, so durability properties are the same as well and were not evaluated again. In the following tests we concentrate on the properties of the commercial biofilm used as mulch material.
5.2.1. Artificial weathering
For this thin film material QUV-A tests were performed.
The properties of the original biofilm are strongly resembling the once of a reference PE-foil that can be used as groundcover. However in this case a severe drop in properties is observed as function of the artificial weathering in the QUV-A test conditions. After 1000 hours QUV-A the elongation at break is reduced to 25%. After 2000 hours these film materials are so brittle that they are difficult to handle and are even damaged when preparing samples for testing. Further testing is becoming impossible although the intrinsic tenacity was only reduced by 50%. Based on these results it can already be expected that the film will have an insufficient resistance for
long term usage.
5.2.2. Weathering in field conditions
Field tests are acknowledging that the selected commercial biofilm has a limited and insufficient durability. After 1 year most of the film material was either damaged or was so weak that mechanical tests could hardly be performed.
Therefore it should be concluded the selected biofilm can maximum survive 1 year in field tests and is not appropriate to be used for groundcover application in forestation where several years of retained functionality is requested. Alternative biofilms, differing in composition, are available in the market with a much longer durability. The possibility of combining a biofilm with an injection moulded biopolymer rim still can be maintained if an appropriate biofilm with a high durability is selected.
5.3. Degradation of the groundcover made of woven jute treated with bioresin (La Zeloise)
5.3.1. Artificial weathering
For the Jute materials both reference jute fabric without additional treatment, as well as the novel developed bioresin treated groundcover were evaluated in the artificial weathering test. Due to the aggressive conditions a fast drop in mechanical properties of the materials is observed. The novel bioresin treated material, shows a considerably improved stability, as can be observed in figure 2. Due to the initial high tenacity of the Jute fabric the resin treated material still has a sufficient tenacity to retain its functional integrity.
5.3.2. Weathering in field conditions
Due to influence of water, illumination and microorganisms, jute has a limited durability when used in the fields. In southern countries like Spain the lifetime of a standard jute groundcover is often not more than 1 year. In the trials of the project, although a fast reduction in tenacity is observed for the jute based groundcover, the material retained its integrity thanks to the initial high strength of the fabric. The groundcovers were still largely intact after 18 months unless damages were made by wildlife (e.g wild boar). The tenacity after 18 months is still of the same order or even higher than the original strength of groundcovers based on PE-film (± 40 N). So the material keeps its functionality, if no external forces are put on the material. Nevertheless it can be expected that the material, will lose its functionality during the third season. Therefor we can conclude that bioresin treated jute fabric will resists biodegradation during 2, maximum 3 years, in function of the climate circumstances.
5.4. Degradation of the groundcover made of recycled rubber (EcoRub)
5.4.1. Artificial weathering
Since it is expected that the material has an extremely long lifetime, artificial durability tests were performed with the more aggressive QUV-B test conditions. As can be expected for a rubber material, the product has a high elongation at break, a rather low e-modulus and a high tenacity. Although some fluctuations are observed only a limited tendency for a reduction in elongation at break and tenacity is observed after 2000 h of aggressive Q-UVB treatment. Since under these harsh conditions only a minor reduction in properties is observed we can already expect by extrapolation that such materials well be extremely durable.
5.4.2. Weathering in field conditions
No or only minor fluctuations in properties like tenacity and elongation modulus can be observed. Also strain is hardly influenced by the field tests after 18 months. The limited variations are largely based on variation in between samples and cannot be assigned to significant differences due to variations in function of time or in between climate zones.
It is concluded that after 18 months, the rubber groundcovers have fully kept their original properties and no significant deterioration of properties can be observed. Long-term extrapolation is difficult to make based on a 18 months field trial but in combination with the minor changes observed in the 2000 h tests under QUV-B conditions , it can be expected that the rubber mats will survive extremely well, and will last for probably more than 10 or even 15 years in outdoor applications. This implies that the material could be reused in several consecutive plantation trials or can be used as a permanent groundcover in for instance urban landscaping applications.
6. Main conclusions about each novel technique
6.1. Innovative soil conditioner (TCU+20G, TCU+40g, TCU+80g):
- The innovative soil conditioner had a positive effect especially in sites limited by the poor and light soil (Semiarid and Montane conditions), especially where water deficit is severe (the former, field trials 1 and 2). In these conditions, this technique improved survival and aerial and subterranean growth rates, as well as water status. In Montane conditions the most relevant positive effect was detected on tree growth.
- In rich sites, with fertile and heavy soil and well provided with water this technique did not have in general a remarkable effect, and only survival rate in Field trial 4 was improved.
- The innovative formulation led to results in general similar to the commercial version of TerraCottem Universal, indicating that it represents an interesting alternative to it. Moreover, it provided generally better results than the alternative soil conditioner tested in Field trial 4 (Hydrogel and Peat).
- The dose prescribed for small to medium sized seedlings (40 g/tree) seem to be the most cost-effective, provided that in general it leads to better results than the lower dose (20 g/tree) and generally not worse than in the case of the higher dose (80 g/tree).
6.2. Biodegradable full plate biopolymer groundcover (FULLPLATE)
- This technique was only tested in Field trials 7 and 8, and not for all variables. This technique provided in general results similar to those from BIOPOLYMER.
- This product seems to have an adequate durability, estimated in around 5 years.
6.3. Biodegradable framed biopolymer groundcover (BIOPOLYMER)
- This technique proved being an interesting option for increasing above and belowground growth in all the conditions tested, compared to NoWeeding trees, to CommHerbicide, to CommBiofilm and, to a lesser extent, to CommPE. This product also led to an increase in soil moisture in highly productive conditions, compared to NoWeeding and to CommHerbicide, and compared to CommBiofilm in the limiting conditions of Field trial 7.
- It can be accepted that this technique has a performance (tree fitness, soil moisture) similar an often superior than the commercial alternatives.
- The only limitation of this technique is the need to fuse the frame to a more resistant biofilm than the version utilized in these field trials, in order to guarantee an acceptable durability.
6.4. Biodegradable woven jute groundcover (JUTE)
- This technique provided results superior than NoWeeding in both limiting and productive sites, with regard to aerial and belowground tree growth. It also increased tree water status in productive conditions.
- The results (tree performance, soil moisture) were similar and often superior to alternative techniques to control competing vegetation: compared to Commherbicide, this technique resulted in higher tree aerial and belowground growth, although the effects with regard to soil moisture and tree water status are not clear. Finally, this technique resulted in higher tree belowground and aerial growth than CommBiofilm in most sites, and also increased soil moisture in semiarid conditions.
- The durability of this technique can be limiting in the case of highly aggressive conditions (high level of UV radiation, sunshine, wind and weed development), with an expected service life of around 3 years. In less aggressive conditions it could have sufficient durability, thanks to the resin treatment.
6.5. Recycled rubber groundcover
- Compared to NoWeeding, this technique resulted in increased tree growth (both aerial anb belowground) in all the conditions tested. Moreover, it led to enhanced soil moisture in areas with severe water deficit (semiarid sites).
- The results were similar and often superior to alternative techniques to control competing vegetation, leading to higher aerial and belowground growth rates than CommHerbicide in productive sites and, less evidently, than CommPE and CommBiofilm in limiting and productive conditions, respectively. It led to higher soil moisture compared to CommHerbicide and to CommBiofilm in most sites, but to lower soil moisture compared to CommPE in general.
- The durability of this technique is expected to reach 15 years, which is an excellent figure for long-term applications including landscaping and gardening.
7. Economic study on the potential interest of soil conditioners and groundcovers in tree planting
7.1. The cost analysis
In the framework of the preparation of the Technical Guide “Soil conditioners and groundcovers for sustainable and cost-efficient tree planting in Europe and the Mediterranean”, done in the framework of Sustaffor project, a cost analysis on the use of the novel techniques and reference techniques was performed. The aim was to assess the potential of these techniques if the choice of the tending operations and plantation techniques depends only on economical criteria, not considering the environmental advantages brought by the novel techniques.
The assumptions of the models were based on real practical data from the use of the techniques (installation productivity rates) and published costs. Different tree planting scenarios were considered, with regard to site accessibility and, in the case of techniques to control competing vegetation, site productivity.
The accessibility scenarios, considered for all techniques, were:
- Flat, easily accessible site. Each round trip to the site for the staff installing or applying the techniques takes 40 minutes.
- Moderate slope (10-20%), intermediately accessible site: each round trip takes 80 minutes and the productivity rate for all activities is reduced compared to the previous scenario.
- Steep slope (30-50%), poorly accessible site: each round trip takes 120 minutes and the productivity rate for all activities is further reduced.
In the cost analysis of techniques aiming at controlling competing vegetation three different levels of site productivity were considered, involving a variable number of required weeding interventions:
- High productivity: weeding is applied twice in years 1, 2, 3 and 4, and once in year 5.
- Medium productivity: weeding is applied once in years 1, 2, 3, 4 and 5.
- Low productivity: weeding is applied once in years 2 and 5.
In chapters 7.2. and 7.3. we present more detailed information from the overall service costs of the different techniques, subject to the different scenarios.
7.2. Cost analysis of techniques aiming at mitigating drought impact
The techniques considered were the application of one and two emergency irrigations and the use of soil conditioner at two doses: 40 g/tree and 100 g/tree. The conclusions of the analysis were the following:
- In all cases, the application of a soil conditioner at the dose prescribed for small to medium sized seedlings (40 g/tree) is cheaper than one emergency irrigation. The difference becomes more evident as accessibility gets intermediate or poor. Only when planting a large number of trees in easily accessible sites the unitary cost of one irrigation is similar to the cost of soil conditioning application at this dose.
- The application of soil conditioner at 100 g/tree dose (prescribed for large seedlings) is more expensive than one emergency irrigation, although for a low number of trees in areas with intermediate to poor accessibility the cost is similar.
- In all cases the application of two emergency irrigations is the most expensive technique.
- Soil conditioning is much less dependent on labour costs than emergency irrigation. The application costs of soil conditioning at the indicated doses vary less than 30% between 12 €/h and 24 €/h labour costs, while the figure rises up to 70% in the case of emergency irrigation.
- The preference for soil conditioning over emergency irrigation becomes more evident as labour costs increase (24 €/h), with the 100 g/tree dose comparable to 1-time irrigation in small plantings at intermediate accessibility sites. However, with cheap labour costs (12 €/h) soil conditioning at the 40 g/dose results in similar costs to one irrigation in easily accessible areas.
- Thus, soil conditioner is an economically feasible alternative to emergency irrigation.
7.3. Cost analysis of techniques aiming at controlling competing vegetation
The techniques considered were the following: mechanical weeding with man-operated tools, chemical weeding (both repeated, reference techniques), plastic groundcover (reference technique), Long-lasting groundcover at two retail price levels (4.5 and 6 €) and biodegradable groundcover at two retail price levels (2 and 3 €). The conclusions of the cost analysis were the following:
- In low productivity sites, where the number of weeding interventions required is low (two or less), mulching is not a suitable option.
- In medium productivity sites, with an expected need for annual weeding during the first five years, herbicide application is the cheapest option although in poorly accessible sites the results are somewhat similar to plastic mulching and to 2 € biodegradable groundcover. In the case that the use of herbicide is restricted, the use of plastic mulching is cheaper than mechanical weeding. The cost of using the 2 € biodegradable or the 4.5 € long-lasting mulch is similar to mechanical weeding in sites with good accessibility, and lower in intermediate to poorly accessible sites. In the latter, even the 3 € biodegradable mulch leads to costs similar to mechanical weeding.
- In highly productive sites, requiring frequent weeding interventions, mulching is the cheapest option. Only the most expensive units (6 € long-lasting and 3 € biodegradable) in easily accessible sites have costs similar to herbicide application.
- The cost of utilizing 4.5 € long-lasting mulches leads to results similar to 2 € biodegradable groundcovers in easily accessible sites, while in intermediate sites the biodegradable option is cheaper. The 6 € long-lasting groundcover provides lower costs than the 3 € biodegradable mulch.
- The attractiveness of biodegradable mulches depends largely on their retail costs. A retail cost of 2 € becomes comparable to 0.9 € plastic mulching in intermediate access sites, and the cost differences are even smaller for poorly accessible sites. The biodegradable units with a retail price of 3 € are not competitive with plastic mulching, according to the analysis. It should be stressed that this analysis does not take into account the environmental and social advantages of the biodegradable groundcovers, which are increasingly taken into account in tree planting.
- The cost of using groundcovers is much less dependent on labour costs than recurrent weeding techniques. The increase in costs of using biodegradable mulches when increasing labour costs from 12 to 24 €/h amounts to 20% while in the case of mechanical and chemical mulching the increases are 65% and 75%, respectively. Both reusable and plastic mulching correspond to increases of around 50% when considering the mentioned rise in labour costs.
- In low productivity conditions mulching remains as an economically unsuitable option compared to chemical or mechanical weeding at any labour cost.
- In medium productivity conditions plastic mulching shows intermediate costs falling between mechanical and chemical weeding at all labour costs, while the economic feasibility of other techniques vary considerably:
* With a high dependence on site accessibility, the cheapest labour costs (12 €/h) makes mechanical weeding falling to lower, similar or higher costs in sites with good, intermediate and poor accessibility (respectively) compared to both 2 € biodegradable mulching and 4.5 € long-lasting mulching.
* With high labour costs (24 €/h) the cost of chemical weeding is lower, similar or higher in sites with good, intermediate and poor accessibility (respectively) as compared to 2 € biodegradable mulching. At this labour cost, the 3 € biodegradable mulch is an alternative to mechanical weeding in sites with intermediate (similar costs) and poor (lower costs) accessibility.
- In high productivity conditions mechanical weeding is the most expensive technique at all labour cost levels. Plastic mulching is cheaper than herbicide application in all cases, while 2 € biodegradable mulching is also cheaper than herbicide application except in easily accessible sites for the lowest labour cost level.
- Among mulching techniques, the use of plastic groundcover leads to the best economic results at the low labour cost level (12 €/h), followed by 4.5 € long-lasting mulching. However, at the highest labour cost level (24 €/h) plastic mulching results in costs similar to or higher than 2 € biodegradable mulching in intermediate and poor accessibility sites, respectively.
- It can be concluded that both biodegradable and long-lasting groundcovers are an economically feasible alternative to reference weeding techniques under certain circumstances.
8. References
Grasset L., Rovira P. & Amblès A. 2009. TMAH-preparative thermochemolysis for the characterization of organic matter in densimetric fractions of a mediterranean forest soil. Journal of Analytical and Applied Pyrolysis, 85, 435-441.
Nelson D.W. & Sommers L.E. (1996): Total carbon, organic carbon, and organic matter. In: D.L. Sparks (ed), Methods of Soil Analysis, Part 3: Chemical Methods. 3rd. Ed. SSSA Book Series nº 5. Madison, USA. pp. 961-1010.
Rovira P., Duguy B. & Romanyà J. 2012. Long-term effects of wildfires on the biochemical quality of soil organic matter: a study on mediterranean shrublands. Geoderma 179-180, 9-19.
Potential Impact:
1. Potential impact
The potential impact of the project is related to the opportunities (technical and socio-environmental, and resulting market ones) that the novel techniques developed during the project imply.
1.1. Technical and socio-environmental opportunities
The novel techniques developed during the project represent new alternatives for mitigating the negative effects of drought and competing vegetation, two of the main threats to tree planting in our conditions, for all types of tree planting projects.
- The new soil conditioner is applied at the moment of planting and represents an alternative to repeated emergency irrigations that result in a massive use of water and fossil fuels.
- The new biodegradable groundcovers are also applied right after planting, allowing optimizing the labour and time resources. These techniques are an alternative to repeated and polluting weeding interventions such as mechanical (i.e. utilizing hand-operated or tractor-pulled machinery) and chemical (using herbicides) weeding, and to plastic mulching, which must be removed at the end of its service life and is built on non-renewable raw materials.
- The new long-lasting groundcover is also an alternative to repeated weeding interventions, and offers the possibility of long-term (e.g. 15 years) use in a single place, or can be reutilized in different areas in shorter periods of time.
As shown in the summary of project results, these techniques have proven to be highly performing, with results similar and often superior to reference (often less sustainable) techniques. Moreover, all of them have areas of application where they are economically cheaper than the reference techniques, and thus there is a market gap where these techniques can be promoted.
Therefore, these techniques and especially the new soil conditioner and the new biodegradable groundcovers are particularly interesting for the following cases:
- Hardly accessible areas: sites located far from populated areas and/or in uneven land or steep slopes, where the application or most reference techniques relying on repeated interventions (emergency irrigation, mechanical or chemical weeding) are expensive to apply.
- Areas where the use of machinery (noise, vulnerable soil or vegetation, etc), plastic mulches or herbicides is restricted by legal, ecological or social constraints: protected areas, parks and gardens, sites with high visual impact, etc.
- Minimal management schemes: areas where it is possible to apply reference techniques (emergency irrigation, mechanical / chemical weeding) but it is intended to reduce their number and intensity because of practical purposes.
- Managers that are open to invest more resources at the beginning of the project if it allows minimizing the time and resources invested during the following years.
- Small tree planting projects, where the unitary cost of any tending operation is high.
1.2. Market opportunities for each novel technique (exploitation of results)
The above mentioned technical and socio-environmental advantages result in market opportunities comprising all the depicted situations, in a range of different types of tree planting: protective forestry (forest landscape restoration, protection of soil and water resources, biodiversity conservation), productive forestry (timber, biomass, cork, nuts, game...) fruit tree planting, landscaping, home gardening, tree nurseries, etc.
The main market opportunities of each novel technique are the following:
1.2.1. New soil conditioner
1.2.1.a Cost level
Price similar to current best-available soil conditioner (Terracottem Universal)
1.2.1.b Key market messages
- Polyacrylamide-free soil conditioner.
- Proprietary mixture of more than twenty components each from different groups all assisting in the plant growth processes in a synergetic way.
- Biodegradable with no toxic degradation products. Expected extended lifetime of ± 8 year.
- 1-time application during planting of trees, avoiding repetitive irrigation during drought periods.
- Proven improved survival rate and growth performance (up to factor 3) for planted trees in soils with poor water and nutrient holding capacity, especially when subject to seasonal water deficit.
- High water absorption capacity and water and nutrient available for the tree offered by the “TerraCottem Universal Plus formulation”.
- Scientifically supported field trials proving the performance;
1.2.1. c Main target markets
- Re/afforestation: all types of productive and protective plantations.
- Urban and private landscaping.
- Nursery production.
1.2.2. Biopolymer-based groundcover, full plate (dimensions foreseen: 50x50 cm)
1.2.2.a Cost level
Intermediate, similar or slightly higher than other biodegradable groundcovers.
1.2.2.b Key market messages
- Fully biobased
- Biodegradable with no toxic degradation products; no removal costs or remaining long-term litter.
- Expected minimum performance service life of ± 5 years for the biopolymer full plate and for biofoil with injection moulded biopolymer rim if biofoil is selected appropriately
- No need for mechanical or chemical weeding (reduced maintenance costs)
- The foil or plate reduces transmission of air and water (humidity).
- Complete blockage of weed growth.
- Easy to install if the design of the plate is appropriately adapted.
- Colour can be selected; dark colours tend to accumulate heat, light colours reflect the sunlight.
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Scientifically supported field trials prove the performance superior to unweeded trees, generally better than herbicide application and similar to standard plastic mulching.
1.2.2. c Main target markets
- Re/afforestation: due to raised cost level and limited size only applicable for plantations with trees of a high cost range and slow growth, requiring at least 5 years without significant weed competence
- Potential for productive plantations and urban landscaping
1.2.3. Biopolymer-based frame groundcover (DTC)
The company producing the framed biopolymer groundcover (DTC) has decided, for the moment, not putting this product in the market, until finding a suitable commercial layer to which fusing the frame.
1.2.4. Biodegradable woven jute treated with bio-resin
1.2.4.a Cost level
Similar to commercially available biodegradable films, which is approximately the double of a polyethylene film.
1.2.4.b Key market messages
- Fully biobased (both resin and fibre).
- Biodegradable with no toxic degradation products (degrades within ± 3 years, depending on the site conditions).
- Expected extended service life of ± 3 years. Material fully disintegrates and acts as organic compost. Avoids removal costs or remaining long term litter.
- Offers ecologic and economic alternative for chemical & mechanical weeding
- No need for mechanical or chemical weeding (reduced maintenance costs)
- Permeable to air and water at the root zone. Proven positive impact on root growth
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Easy to install.
- Natural aesthetic look, easily “integrates” in the natural environment.
- Size and shape can be changed on the demand of client
1.2.4.c Main target markets
- High application potential in re/afforestation, both productive and protective
- Urban landscaping and areas with high visual pressure
- Weed control only required during first 3 years: fast-growing trees, possibility to perform further weeding interventions.
1.2.5. Long-lasting groundcover made of recycled rubber (dimensions foreseen: 40 cm diameter)
1.2.5.a Cost level
High, around 4 times higher than polyethylene film
1.2.5.b Key market messages:
- Fully produced from recycled materials (offering a second life to rubber wastes).
- Durable material with expected lifetime of at least of up to 15 years under outdoor conditions, and to be reused during several plantation cycles. After useful lifetime, the groundcover should be recovered from the field and reused in new plantations (unless long-term prevention of weed growth should be guaranteed for longer e.g. trees in an urban environment).
- Preventing weed growth and enhancing growth of planted trees - scientific and statistical proven effects: trees performs better than in the absence of any weeding technique; trees perform better for some variables than mechanical or chemical weeding; results are in general similar to the plastic-based commercial groundcovers; possible synergetic effects with soil conditioner application in areas with soils having a poor water and nutrient retention capacity and subject to water deficit
- Closed foil or plate reduces soil water evaporation.
- Complete blockage of weed growth, due to its dense structure.
- Easy to install, self-laying potential due to density of 2.9 kg/m².
- Black colour prevents penetration of light and results in accumulation of heat underneath the plant.
1.2.5.c Main target markets
- Landscaping for long-term suppression of weed growth near the stem of a tree (thus it can be an excellent complement to mechanical weeding or mowing, avoiding tree damage).
- Reusable pot discs (small sizes) for nursery applications
2. Dissemination activities
2.1. Objectives of dissemination
The dissemination activities performed during the project have followed a range of objectives:
- Raise awareness about innovative techniques for more efficient and sustainable tree planting, alternative to the limited current options. The target groups are the society in general, practitioners and managers, companies, researchers and policy makers.
- Create a space for open discussion among managers and technicians about the need for developing new methods for tending and managing tree planting projects
- Introduce the novel techniques, their rationale, performance and opportunities
- Increase the capacity of the SMEs participating in the project for exploiting commercially their products from an eco-innovation prospective
2.2. List of Sustaffor dissemination activities
The main dissemination activities were the following:
2.2.1. Webpage: the webpage is the basic infrastructure for project presentation and dissemination of results and outcomes, worldwide. It is programmed in both English and Spanish. The address is www.sustaffor.eu. It has been updated regularly with the main events and preliminary results of the project, and has been disseminated in all the public events where a Sustaffor partner has participated. It is expected to keep it online during at least 5 years.
2.2.2. Brochure: an 8-pages brochure was prepared in both electronic and paper versions (2,000 units), introducing the project concept, aims, novel techniques, partners and experimental activities. The paper version was distributed in all the activities where a Sustaffor partner has participated. An additional version of the electronic version was produced in Spanish. Moreover, the electronic version of the brochure was updated at the end of the project, with a new 12-pages format including a summary of the results of the field trials and a final page with the conclusions.
2.2.3. Roll-up: a roll-up summarizing the project was provided to each SME, to be utilized in all the commercial fairs where they participate.
2.2.4. Final seminar: the project and its main outcomes were presented on December 16th, 2015 in Solsona (Spain). The audience included members of the Catalan and Andorran public administration, forest, agriculture and gardening companies and forest and agriculture owners. Professor Jordi Cortina, Head of the European Chapter of the Society for Ecological Restoration was invited as guest speaker.
2.2.5. Individual novel techniques leaflets: a 2-page leaflet was produced for each company, where the main technical and environmental advantages of each novel technique are presented. These documents have a clear commercial orientation. They are produced in electronic and paper format, in English, Spanish, French and Polish.
2.2.6. Video-presentation: A 4.5 minutes video has been produced for the broad dissemination of Sustaffor activities and results. This video has been located in the project webpage and has been provided to all the partners for its dissemination.
2.2.7. Newsletters: five periodic electronic newsletters, with 5 to 12 pages each, were produced and sent by e-mail to the professional distribution list of each partner.
- Newsletter 1: Sustaffor project launched! (February 2014)
- Newsletter 2: Sustaffor field trials accomplished! (May 2014)
- Newsletter 3: Sustaffor field trials monitoring (March 2015)
- Newsletter 4: Some preliminary results from the first vegetative period (July 2015)
- Newsletter 5: Sustaffor comes to an end...here are some of the main conclusions (December 2015)
2.2.8. On-field workshops: taking place in the field trials, these half-day technical meetings allowed introducing and discussing the concept and aims of the project to end-users and managers, as well as the experimental design, available results and how to install and manage the novel techniques. The two on-field workshops were:
- Reforestació de terrenys agrícoles a mínim cost (June 2015)
- Noves tècniques de plantació d?arbres: sostenibilitat i eficiència (December 2015)
2.2.9. Trade fairs: the SMEs have presented their involvement in an EU-funded research project, as well as the novel techniques developed, in seven different trade fairs of national and international level. Most of them were performed by the SMEs commercializing the products (Ceres and Terrezu). The fairs were:
- Gardenia 2014 (Poznan, Poland, February 2014)
- Green if Life 2014 (Warsaw, Poland, August 2014)
- International Gardening Days 2014 (Goluchow, Poland, September 2014)
- GreenExpo 2014 (Gent, Belgium, September 2014)
- Gardenia 2015 (Poznan, Poland, February 2015)
- Green if Life 2015 (Warsaw, Poland, August 2015)
- Bionoain 2015 (Noain, Spain, September 2015)
2.2.10. Training activities: these training are addressed at the SMEs participating in the project and to their commercial partners that they invited to participate. In both cases the training was performed by CTFC staff and guest speakers.
The first training took place in Poznan (Poland) in February 2015, during the international fair “Gardenia”. The topic was “Reforestation in Europe: trends, techniques and economics”. The guest speaker was Francisco Lario, from the Spanish public company TRAGSA.
The second training took place in Navarra (Spain) in October 2015, titled “Performance of Sustaffor novel techniques, labelling, market opportunities”. The guest speakers were Anna Esteve, expert on eco-labelling from the Catalan public administration, and Gregorio Borge, from the Spanish SME Zicla, specialized on the fabrication of eco-friendly products.
2.2.11. Appearances in Mass media_ a set of five press releases addressed to the mass media have been prepared, in order to disseminate the project and its outcomes among the broad public. Moreover, two participations were performed in radio and TV.
Following this link, it is possible to check the TV programme broadcasted in the Catalan TV:
http://www.ccma.cat/tv3/alacarta/programa/Arbres-Solsona/video/5224971/
Following this link, it is possible to check the radio program where Míriam Piqué, project coordinator, was interviewed:
http://www.ccma.cat/catradio/alacarta/informatius-catalunya-radio/el-primer-sector-la-gamba-de-palamos-de-la-barca-a-casa/audio/906343/
2.2.12. Participation in technical conferences: the RTDs have participated in (or submitted communications to) eight high-level technical conferences, either with posters or oral communications. The conferences are held at different geographic and thematic approaches. These technical conferences were:
- EU 1st Textile Flagship Conference (Brussels, October 2014)
- Meeting on European Funding for SME innovation (Solsona, December 2014)
- IV Mediterranean Forest Week (Barcelona, March 2015)
- Euratex 2015 (Brussels, March 2015)
- Reforestation Challenges (Belgrade, June 2015)
- SISEF National Congress (Florence, September 2015)
- III Joint meeting of the Spanish Society of Forest Sciences – Working Group on Afforestation and the Spanish Association of Land Ecology (Lugo, October 2015).
Moreover, an abstract was submitted to the 21st International Symposium on Analytical and Applied Pyrolysis, to be held in Nancy in May 2016.
2.2.13. Technical guide: “Soil conditioners and groundcovers for sustainable and cost-efficient tree planting in Europe and the Mediterranean”. This manual, oriented to final-users and managers, presents the challenge of tree planting in Europe and the Mediterranean and options for tackling drought and competing vegetation, including a cost analysis of various options. A special focus is done in the potential of the novel techniques developed during the project. It has been produced in Spanish (electronic and paper versions), English (electronic) and French (electronic).
2.2.14. Articles in technical journals: during the project, seven technical papers have been produced and published or submitted to different technical journals related to forestry, environmental sciences, landscaping and agriculture, with various geographical scopes. In these articles, the project and its main outcomes and results were presented, addressed to technical public of different background: policy makers, managers, practitioners and companies. Moreover, the publications in the proceedings of the mentioned conferences (2.2.13) are also considered in this group of publications. The list of technical papers is as follows:
- Coello J, Rovira P, Fuentes C, Piqué M. (2016). Eficacia y sostenibilidad en restauración forestal: nuevos acondicionadores y cubiertas del suelo. Proceedings of the III Joint meeting of the Spanish Society of Forest Sciences – Working Group on Afforestation and the Spanish Association of Land Ecology (Lugo, October 2015). Press
- Coello J, Piqué M. (2016). Condicionadors i cobertes del sòl per a plantacions forestals més sostenibles i eficients. Silvicultura (press)
- Coello J, Piqué M, Rovira P, Fuentes C. (2016). Intérêt de l’amendement et du paillage pour les plantations forestières en région méditerranéenne : le projet FP7 Sustaffor. Forêt-Méditerranéene (press)
- Coello J, Cortina J, Valdecantos A, Varela E. (2015). Forest landscape restoration experiences in southern Europe: sustainable techniques for enhancing early tree performance. Unasylva 245 (66): 82-90
- Coello J, Rovira P, Fuentes C, Piqué M. (2015). SUSTAFFOR project: soil conditioners and groundcovers for tree planting (Proyecto SUSTAFFOR: acondicionadores de suelo y acolchados para plantaciones forestales). Navarra Forestal 37: 35-37
- Coello J, Piqué M, Rovira P, Fuentes C. (2015). Innovation in sustainable afforestation techniques (Innovació en tècniques sostenibles de reforestació). Catalunya Forestal 126: 5-10
- Coello J, Fuentes C, Piqué M. (2015). Innovative soil conditioning and mulching techniques for forest restoration in Mediterranean conditions. In: Ivetic V., Stankovic D. (eds.) Proceedings: International conference Reforestation Challenges. 3-6 June 2015, Belgrade, Serbia. Reforesta. 201-210.
2.2.15. SCI journals: three scientific papers (peer-reviewed in indexed journals) have been produced and submitted in December 2015, being addressed at researchers. These publications have been coordinated by CTFC and CNRS, and are based on the results from the field and laboratory trials. The list of papers are as follows:
- Vitone A, Coello J, Piqué M, Rovira P. (2016). Use of soil conditioners and mulching innovative groundcovers in Mediterranean re/afforestations: aerial and belowground effects in hybrid walnut. Submitted to iForest
- Coello J, Fuentes C, Rovira P, Piqué M. (2016). Improving seedling survival and growth in mountain forest restoration: combined effect of mulching and soil conditioners. Submitted to European Journal of Forest Research
- Abdelli G, Al Husseini A, Rovira P, Grasset L. (2016). Thermochemolysis for the simultaneous analysis of the main biomolecular families in soil. application to the mesurement of the impact of inovative renewable practices for reforestation in a climate change context. Submitted to Journal of Analytical and Applied Pyrolysis
List of Websites:
The project webpage is www.sustaffor.eu
Contact details of the coordinator (CTFC):
Project coordinator: Míriam Piqué
Technical manager: Jaime Coello
Administrative and financial coordinator: Dúnia Riu
sustaffor.info@ctfc.cat
Phone: +34 973 481 752
