The relationship between plant species richness and productivity on a watershed in southern French Alps was studied. Few studies have considered looking at previous land use when determining the relationship between species richness and biomass. The results indicate that productivity is a decreasing log-linear function of succession age. At a landscape level, the overall relationship between specific richness and productivity was found to be a log-linear function, as well as at a local scale, thus not in conformity with hump-back relationship usually presented. Moreover for the same level of productivity, the ancient forests would contain more species than the recent forests. In grasslands and shrubland, limiting resources and microtopography control the species richness. The peak of richness observed in grasslands for a productivity between 100 and 200 g.m-2 indicated that grassland and shrub communities are probably unsaturated. Broadly it appears that the grazing has no overall effect on productivity nor on species richness per m2 level. However sward dominance by Brachypodium pinnatum makes fall both the productivity and the specific richness. Therefore consequences for biodiversity conservation is questionable.