Search for factors responsible for maintaining the rich bryoflore in terricole isolated habitats

Quantitative analysis based on 93 bryophytoecological releves and on exhaus tive inventories from six forest structures (dense stands of Quercus ilex o r Quercus suber) of different surfaces, isolated within the vineyard near P ierrefeu-du-Var, the outlying contact zones I (shrubby vegetation) and i (h erbaceous vegetation) and the neighbouring vineyards. The results show that the contact zones take a rather limited reserve part in the maintenance of the global richness in terricolous bryophytes (RGB) of the forest structur es, because the former are richer in photophilous and nitratophilous taxa t han the latter. For what concerns the richness in terricolous forest bryoph ytes (RBF), the contact zones at the Defens-du-Becasson (northern exposure, surface = 77 617 m(2)) are particularly humid and shady. They house a nota ble number of hygrosciophilous and xerosciophilous forest bryophytes. Their role in the maintenance of the RBF of the forest zone is consequently more important than in the other studied stations which correspond to islets an d hedges of more reduced surface (13 115 to 1165 m(2)), located in a dry en vironment. (C) 2001 Adac/Editions scientifiques et medicales Elsevier SAS.