Functional responses of calcareous grassland sites to agrarian and ecological factors in the French pre-Alpine region

The identification of functional groups in calcareous grasslands of souther n Vercors (Rhone-Alpes, France) is investigated through relationships betwe en biological traits of the species and agro-ecological factors. Community patterns are determined by (i) the level of edaphic stress (oligotrophy and xericity) and (ii) the regime and the intensity of agropastoral management (grazing and mechanical cutting). In such grasslands submitted to regular disturbance, life traits related to dispersal and regeneration processes ha ve greater importance for the differentiation of species than morphological traits, and Grime's adaptative strategies are the best predictors of speci es ordination on agro-ecological gradients (e.g., stress and disturbance). A classification of species in functional groups based on the same life tra its and similar responses to disturbances is proposed, and its role in defi ning adequate conservation management of calcareous grassland by low-intens ity livestock farming is discussed. The functional role of grazing is empha sized by the relationship between species dominance or rarity and their lev els of consumption and dispersion by sheeps. In calcareous grassland commun ities, dominant species are the most palatable and the most dispersed by sh eeps, while rarer species depend on other dispersal modes, such as seed rai n or mowing machinery.