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Linking tree and belowground biodiversity to forest Ecosystem function

Final Report Summary - LINKTOFUN (Linking tree and belowground biodiversity to forest Ecosystem function)

Linking tree and belowground biodiversity to forest Ecosystem function


It has been estimated that over two thirds of terrestrial biodiversity occurs in forests, emphasizing the importance of understanding the main drivers of diversity and of sustaining these ecosystems in the face of rapid climate change. Apart from being a major source of biodiversity and its conservation, European forests are of immense importance to both society and the environment, providing services that include timber and non-timber products, carbon sequestration and biogeochemical cycling, water catchment protection, climate regulation, landscape benefits and protection against avalanche, flooding and landslides. One of the important ecosystem services provided by forests is carbon sequestration: soil contains twice as much C compared to the atmosphere and two-three times more than the amount stored in the vegetation biomass. Soil C may comprise as much as 85% of the terrestrial C stock in boreal forests, 60% in temperate forests and 50% in tropical rain forests. The size of the C pools in forest soils is related to the amounts of C entering the systems through the remains of roots, mycorrhizal hyphae, microbial biomass, leaf and needle litter and to the loss of C through respiration or leaching of dissolved organic carbon. There is a growing recognition that biodiversity and the underlying complexity of ecological processes in forest ecosystems are of central importance to each of the functions attributed to forests; it is also understood that forest ecosystem resilience and adaptive capacity in the face of climate change is strongly linked to biodiversity.
The LINKTOFUN project focused on comparisons between natural forest ecosystems, managed forests, and plantation mixtures. The project attempted to link forest biodiversity to ecosystem function in a number of forest types. The work carried out to meet the major scientific objectives of LINKTOFUN have been supported by three grants to investigate forest disturbance and soil carbon dynamics, and one major grant to investigate the role of tree and mycorrhizal biodiversity in soil carbon dynamics in Ethiopian forests. Work in Ethiopia permitted a rare opportunity to work on natural forests with a high tree biodiversity. Three projects to investigate forest disturbance and soil carbon dynamics supported work carried out at sites in the calcareous Alps, and at the high instrumented sites at Zöbelboden and Rosalia. Work investigating the ecological function of mycorrhizal communities was carried out at a tree line site in the Austrian Alps. A tree biodiversity manipulation site (B-Tree) was established as part of the Tree Diversity Network (
In the work in Ethiopia funded by the CARBOPART project, five sites were established along a climatic gradient in Amhara region in North Ethiopia. In this gradient the annual precipitation varies 900 to 2200 mm per year, and the mean annual temperature from 15 to 27 ºC. At each site C inputs into soil via leaves and fine roots in relation to tree biodiversity was investigated. High interspecific variability in leaf traits among woody species coexisting naturally in Ethiopian highland forest ecosystems was shown. Strong relationship between the most important leaf morphology trait (specific leaf area) and leaf chemical composition (nitrogen and phosphorus concentration) were found. Especially deciduous and evergreen species differed in important leaf traits like N and P concentrations and leaf toughness. Morphological traits of absorptive roots showed significant difference between species but less traits differed significantly in the 0-5 mm diameter roots. Specific root length and specific root area of absorptive roots were significantly different between functional groups. Chemical traits such a lignin content differed between species and some functional groups. The results indicate that root traits of woody species in diverse Afromontane dryland forest differ widely between species.
Ectomycorrhizal community structure was determined at a tree line sites and a potassium addition experiment in the Austrian alps. At a tree line site, the ectomycorrhizal community structure was determined on Picea abies and Pinus mugo. The activity of a number of enzymes was determined on the dominant ectomycorrhizas for each tree species. In soil, the activity of a range of enzymes was determined from soil under the tree species and under Rhododendron hirsutum. The ectomycorrhizal community structure differed between Pinus mugo and Picea abies at the higher elevation site, but also between the higher and lower elevation Picea abies sites. At the higher altitude Picea abies site, the ectomycorrhizal community was dominated by Cortinarius sp., whereas at the lower elevation site the community was dominated by Russula. In Pinus mugo the dominant species were Amanita muscaria and Russula orchroleuca. The community structure of the ectomycorrhizal community of Picea abies and Pinus mugo differed strongly, but the average activity of surface enzymes of the ectomycorrhizal communities was similar. Our results suggest that different combinations of species and types of mycorrhizal fungi support a similar ecosystem function in soils. In a literature review the structural traits of ectomycorrhizal communities of three important tree species in European forests, namely Fagus sylvatica, Picea abies and Pinus sylvestris were investigated. A common pattern in the community structure was a small number of abundant taxa and a large number of rare taxa. Root colonising taxa appear to be selected from a larger taxa pool in the soil. Host tree species is the most important factor for shaping the ectomycorrhizal community. Superimposed upon the filtering effect of the host tree are factors such as soil properties, temperature and precipitation. Rarity occurs as low abundance at one site, and low frequency across numerous sites. We suggest that rare taxa are maintained by the high dynamics of the root system through root turnover, with exchange of C for nutrients further acting as a mechanism of functional selection.
Estimation of soil CO2 efflux was carried out at two sites in the calcareous Alps supported by the Startclim and the C-Alps project. The sites are dominated by spruce (Picea abies) and beech (Fagus sylvatica). Spruce stands at the site were affected by large windthrows in 2007 and 2009, thus providing a pseudo-chronosequence to allow investigation of temporal changes after disturbance. It was shown that the activity of the roots and fungi on the 2007 windthrow had recovered to levels found in the intact forest. Thus suggests that measures to re-vegetate windthrows more rapidly may prevent soil C loss. Along the chronosequence, structural equation modelling revealed that soil temperature, soil moisture, SOM properties, and plant community composition explained 90% of the in soil respiration. While no direct interactions among plants and SOM properties could be determined, plants significantly affected soil microclimate. Our results show that soil heterotrophic respiration dominated soil respiration after forest windthrow. Since fresh litter inputs were marginal and average C losses from soil heterotrophic respiration and SOC stocks were in the same order of magnitude, this study demonstrates that post-windthrow declines in SOC stocks were driven by a temperature-related increase in soil heterotrophic respiration.

Prof Douglas Godbold, Institute of Forest Ecology, Universität für Bodenkultur, Vienna, Austria.