The cork oak forests of the north west zone of the mediterranean basin are often degraded, invaded by shrubs and susceptible to fire. Their renovation is possible by mechanical shrub clearing eventually associated with grazing animals to control shrub regrowth.
The objective of the project is to compare the effects of three management techniques of cork oak forest on forest productivity, on fire prevention and on forest regeneration. The techniques are:
shrub clearing, pasture seeding and animal grazing;
control, without shrub clearing or animal grazing
The project studied 2 agrosylvopastoral treatments (shrub clearance with or without grazing) and their influence on production, fire protection and the regeneration of cork oak forests in southern France, northern Spain and Sardinia. The sylvopastoral treatments were found to have a strong positive influence on the longitudinal growth of the tree, although this influence seemed to decrease after a few years. The evolution of the vegetation after the shrub clearance was found to be very dynamic and the effects of clearance have almost disappeared after 5 to 7 years. The efficiency of the undergrowth control by grazing varied according to the grazing animal species and management by the farmer. The regeneration rate of cork oaks was decreased in grazed plots compared to the untouched plot, but it was still found well sufficient for regeneration. Moreover, when the number of regeneration units decreased the units were found to be more vigorous.
A total of 8 or 10 typical sites were chosen in representative areas: Pyrenees Orientales (France), Catalonia (Spain), Sardinia (Italy). On each site the three management techniques are tested on the same homogeneous forest. Data from the three techniques will be grouped under 5 chapters.
Cork yield and cork quality:
cork yield directly measured after removal or estimated;
quality estimated on cork samples based on 4 criteria: cork thickness, porosity, density, sanitary status.
Cork growth and physiology:
longitudinal growth by measurement of growth segments;
radial growth by dendrometry and automatic analysis of rings on wood and cork samples;
biomass return to the soil (leaves, branches, acorns);
mineral state of the leaves by foliar analysis.
Phytosanitary state (fungus and insects).
distribution of seedling and forest structuration by diameter;
testing of individual plastic shelters for young plantations associated with animal grazing.
Estimation and evolution of shrub stratum biomass and structure:
This aspect is linked to fire protection.
Expected results concern renovation of cork oak forests, improvement of cork oak production and fire protection of approximately 200,000 ha of mediterranean forests. Data on growth, production, mineral nutrition, will provide a base for a biological assessment of the three techniques and enable the identification of the different factors involved in cork production in the short term.
Fire protection and forest regeneration are the key points of oak production in the long term. Analysis of the genetic variability of the cork oak will constitute the basis of selection of promising varieties.
Funding SchemeCSC - Cost-sharing contracts
07029 Tempio Pausania Sassari