Management of grazed ecosystems in extensified conditions: Relevance of functional ecology and research prospects, applied to moist middle mountains

According to the situations encountered in extensified breeding farms, thre e important pieces of ecological knowledge allow to understand grassland ec osystem dynamics, in order to settle sustainable pasture management in both production and environmental aims. i) The interaction between vegetation a nd herbivores must be considered as well as the long term adaptation betwee n vegetation status and stocking rate, or as the instantaneous modulation o f grassland production and structure under herbivore predation. ii) The dyn amics of botanical composition must be represented in terms of sensitivity and resilience to perturbations or to management changes, which condition p rimary phytomass production and accumulation. Extensifying grassland manage ment induces reversible effects on the seasonal dynamics of the phytomass, but cumulative negative effects on botanical composition. Species strategie s are involved in the dynamics of the spatial structure and diversity of th e vegetation. iii) The management of the nitrogen cycle allows to manipulat e in a long term the soil nitrogen supplying capacity, for improving the pe rennity of sowed swards, or making easier the control of the phytomass unde r low stocking rates. The implications for N leaching are discussed. (C) El sevier/Inra.