Proposal for a parametrization of site conditions in the Mitrakos' indices.

The influence of slope gradient and exposure, of altitude and of distance from the sea on the winter and summer stresses sustained by the Mediterranean vegetation have been parametrized. An example of vegetation changes driven by the variation of any of such environmental factors is reported, and a mathematical formula is proposed to determine a monthly value to add to or subtract from the drought stress and cold stress values, estimated by the Mitrakos' index, in order to better approximate reality. Values obtained in such way can be used in synecology and phytosociology to express in a synthetic-correlative way the ecological valence of plant communities with respect to the main physiognomical features of their growing sites.