Biodiversity and grass production in grasslands liable to flooding: an attempt to simulate production

The alluvial Saone Valley (France) is designed as a special area of nature conservation. Permanent grasslands in this area are special ecosystems as far as their use is concerned: conservation of biodiversity, protection of water resources, flooding management, forage supplies. The prediction of grass production in these grasslands is studied in order to evaluate the impacts on grass production of a measure considered for the conservation of habitats (cutting delay) The botanical composition observed in 15 patche s from 2001 to 2004 showed high number of species, according to grassland management and topographical localisation. The dates of flowering spread out from mid-May for the earliest to mid-July for the latest. Moreover, the botanical composition can vary between years as a function of the climate and especially the duration of flooding. It is an ability of these natural grasslands to adapt to climatic conditions. We attempt to estimate the production of these grasslands with the crop model STICS adapted for grass production. The simulations have to be improved by taking into account the variation of botanical composition during the first growth, the particular conditions of mineralization of organic matter in the soil and a better characterisation of flooding duration.