Functional reactions of mediterranean sclerophyllous ecosystems to clearing impact.

Clearing brings about disturbances with manifold effects on vegetation. The authors analyse the consequences of these disturbances on soil, and on the Quercus ilex and Arbutus unedo nutrients. On calcareous soils, these distu rbances cause significant decreases in the carbon ratio, the humic compound s concentration, and the cation exchange capacity. On siliceous soils, only the humic compounds concentration decreases significantly. The nutrients c oncentrations and seasonal dynamics are disturbed differently according to the species and the substrate. Only a significant decrease of nitrogen is o bserved in Quercus ilex on siliceous soils, whereas Arbutus unedo shows, in addition, significant variations in phosphorus, magnesium and calcium on c alcareous soils.