Article

Processing (FAC) of 80 bryophytoecological relevés from the north-westem border of tbe Maures massif (Var, France, siliceous bed-rock) shows that the main factors determining bryodiversity within the domain of lawns of the Tuberarietea guttatae Rivas-Goday 1957 are tbe degree of substratum stability and second1y the edaphic humidity. Three communities of bryophytes have been distiRguished : the thermo-hygrophilous association with Campylopus pilifer and Bryum alpinum Hébrard 1970 corro Hébrard, Loisel & Jauffret, on the bottom of bowls on rocky flags, the dense and more xerophilous formations with Pleurochaete squarrosa and the diffuse and fugacious community witb Archidium alternifolium, Entosthodon obtusus and Riccia michelii which occurs in c\earings within scrubs and on the edge oftracks. A crossing of the bryofloristical data and some mesologic and edaphic variables revealed that the discriminant factors are the cover values of bryophytes and therophytes, the slope, the degree ofisolation ofthe relevés and tbe depth ofthe soil, the percentage ofbare soil, the number of species of bryophytes and the surface of the habitats. Thus, the bryophytic cover increases with tbe value of the slope and of the cover of tberophytes, whereas the number of species of bryophytes decreases in isolated habitats of reduced surface (bowls with Campylopus pilifer). FinaIly, the adequation between the communities of bryophytes and the edaphic variables is bado