Predicted effects of climate change on a Mediterranean keystone plant species

Keystone plant species are known to provide various essential ecosystem services. The Mediterranean keystone species Stipa tenacissima improves soil functioning and facilitates the establishment of different plant species, so it is used in restoration programmes. In this paper, we aimed to predict the impacts of climate (aridity) and soil texture (sand content) on the establishment and development of S. tenacissima (number, cover and width of tussocks) and on soil properties underneath S. tenacissima tussocks. This research demonstrated a significant positive effect of S. tenacissima on LFA (landscape function analysis) indices, revealing the importance of this key species in the soil stabilization, water infiltration and nutrient cycling. Similarly, soil nutrient contents (organic carbon and total nitrogen) and enzyme activities (ß-glucosidase and phosphatase) were highly improved underneath S. tenacissima compared to bare ground areas. However, increases of aridity and sand content showed strong negative effects on soil organic carbon, total nitrogen and activities of the hydrolytic enzymes both on bare ground areas and underneath S. tenacissima tussocks. Furthermore, we found that the climate is the main controller of the number of S. tenacissima tussocks, cover and width. Soil sand content influences the colonization of S. tenacissima, as it affects soil water potentials. In general, this study demonstrates the non-sustainability of S. tenacissima under a warmer and drier climate, which will negatively affect its ability to create islands of fertility in South Mediterranean grasslands.