Conservation and recovering of cork oak forests. First results of cooperation between Sardinia (Italy) and Tunisia

Cork is an important natural resource for the economy of southern European and North African countries. In these areas, large productive cork oak forests are declining and cork quality is deteriorating due to both the exploitation intensification and the lack of proper management. Therefore, the identification and the study of the degradation factors in Sardinian and Tunisian corkgrowing areas may contribute to provide information on the planning strategies to follow in order to recover the degraded areas. This was, with special attention to the state of soil conservation, the aim of several research projects coordinated by the chair of Geopedology at Cagliari University. Their objectives were achieved with: the identification of representative study areas; their geological, morphological, pedological, climatic, and vegetation survey; the study of land use change and its relationships with forest degradation, the planning of strategies for the recovering of the degraded areas. Four study sites were selected: two in Tunisia (Tabarka and Nefza delegations), and two in Sardinia (Planargia and Gallura). Similar degradation problems, linked to the decay of existing cork oak forests, to the scarcity or absence of renovation and to soil erosion, were observed in the four areas. In each site, test plots were selected on the basis of vegetation cover, lithology and morphological aspects, and the following investigations performed: floristic and vegetation survey; soil survey with description of soil profiles; humus forms; cork oak renovation along transects; cork oak dendrometry. The anthropic activity was assessed by the modification of the forest vegetation structure and, when degradation occurred, by the degree of soil erosion and soil baring. Anthropic activities plaid a main role in cork oak stands degradation process. Major causes are fire, ploughing and overgrazing. Soil erosion, loss of organic matter, absence or reduction of plant regeneration, and loss of vegetation cover are the main processes acting in those areas. The cooperation carried out between Mediterranean countries must be encouraged to increase the knowledge about conservation and recovering strategies for all natural resources.