Grassland ecotopes of the upper Meuse as references for habitats and biodiversity restoration: A synthesis

The river valley of the French upper Meuse and its floodplain, constitutes a relatively natural ecosystem which still contains many endangered species of high conservation value. For example, several birds (Crex crex, Numenius arquata) as well as plant species (Gratiola officinalis, Inula britannica, Teucrium scordium, Ranunculus lingua and Mentha pulegium) which have declined seriously in France in recent times are found in the upper Meuse floodplain. Phytosociological studies and water level measurements have shown that the floristic diversity is mainly influenced by hydrological fluctuations and agricultural practices. The plant communities are structured along a topographical gradient in the high water bed reflecting the duration of floods and the ground water table depth. Agricultural practices have influenced the vegetation changes by selecting species adapted to particular management practices (e.g., fertiliser use, grazing, cutting regime). The data collected in this study from the upper Meuse as enabled 13 grassland and wetland ecotopes to be defined which are correlated with different environmental factors. Fertiliser use, grazing and reduction in the frequency of the cutting lead to a lower species richness because they encourage competitive species. However, it is also demonstrated, that maximum biodiversity is not always synonymous with high conservation value because some impoverished ecosystems, e.g., sedges and tall forb formations, may contain endangered plant and bird species. Knowledge of the boundaries between the different plant communities enables likely changes in floristic composition after modification of one or more site factors to be forecasted. Such factors include, water table depth and flood frequency, cutting regime, fertiliser use and grazing pressure. Thus, the definition of these ecotopes, corresponding to correlations between water regime, agricultural practice and vegetation composition, could lead to the establishment of guidelines for water and agricultural managements that could be involved in restoration projects.