Restauration de pelouses steppiques de Haute-Durance après perturbation du sol

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVINInternational audienceLarge-scale ecological disturbance in grassland is increasing worldwide mainly due to land use changes and habitats destruction. The construction of high-voltage transmission lines in our study area, the Haute-Durance valley in the Southern French Alps, involves a degradation of soil and plant communities along transitory access tracks and construction platforms. In such disturbed ecosystems, restoration is limited by a lack of available propagules and low seedling recruitment due to soil degradation and/or strong summer drought. We focus on the restoration of species-rich dry to mesophilic grasslands covering a large part of the construction zone at an altitude of 1000 to 1400 m. Most of these grasslands are Natura 2000 priority habitats such as N6210 "Semi-natural dry grasslands of Festuco-Brometalia and scrubland facies on calcareous substrates" (EU directive habitat 92/43/EEC). We will present the first results of a study analyzing (1) the appropriate reference community for ecological restoration, (2) hay transfer techniques to overcome dispersal limitation (3) soil preparation to facilitate establishment, (4) the required grazing intensity to favour grassland target species and to avoid the spread of ruderals and shrubs. In a second experiment, we test priority effects on plant succession and restoration by manipulating the arrival order of dominant and subordinate plant species. Due to differences in microclimate and soil conditions depending on slope, orientation of slope and bedrock, plant communities may change at relatively small scales. Additionally, management intensity affects species assemblages. The identification of the appropriate reference community is therefore the first crucial step for successful restoration using hay transfer but also to evaluate the success of restoration efforts. We will present results on environmental drivers of plant species composition. Based on these results we will discuss the required match of source and recipient site conditions in order to restore dry grassland communities in Southern French Alps