EFFECT OF VEGETATION CLEARING ON THE BRYO PHYTE POPULATION OF CERTAINTREE AND SHRUB AREAS THROUGHOUT THE CALCAREOUS RANGE OF THE CENTRAL SECTION OF THE FRENCH DEPARTMENT OF VAR

A study of the effects of vegetation clearing on the bryophyte layer o f two Pinus halepensis forests, a white oak grove and a Rosmarinus off icinalis - Erica multiflora garrigue in the central part of the depart ement Var (calcareous substratum). Vegetation clearing entails a sharp diversity increase in the bryoflora on fire breaks, which is characte rized by a large number of acrocarpous, photophilous and frequently ni trophilous or nitrotolerant mosses. Qualitative analysis of the data ( FAC) shows that vegetation clearing is followed by a local enrichment of the substrate in ammoniacal and nitric nitrogen, and a general impo verishment in organic carbon. The more complete the suppression of tre es or shrubs, the stronger is the impoverishment in organic carbon.