Effects of solar panels and park management on plant functional traits and ecological groups

The growing development of solar parks has resulted in ecosystems with specific environmental conditions including panel shading, rainfall interception by panels and vegetation management, altogether potentially selecting plant species with adapted traits from the local species pool. In this study, we analyzed the functional composition and structure of the vegetation in twenty solar parks of southwestern ( Landes de Gascogne, LAG) and southeastern France ( Provence Alpes Côte d’Azur, PACA), half of the parks being grazed, and the other half being mown. We evaluated differences between the following three microhabitats repeated in four blocks per park: outside panels (never shaded, full rainfall), inter-row (partially shaded, full rainfall) and under panels (constantly shaded, no rainfall). We identified all vascular plant species and estimated their cover and frequency of occurrence. Species means of plant traits and ecological group values were extracted from existing databases. We used RLQ fourth-corner and linear mixed effects models to evaluate links between functional/biological traits and environmental variables, and to examine differences in responses to microhabitats and park management. The microhabitat effect was significant for functional traits, Raunkiær biological types and Ellenberg indicator values. Communities under panels showed traits adapted to cool, humid and shaded conditions. Specific leaf area and leaf dry matter content were lower under panels than outside panels, whereas Rubus -type species were more abundant. Plant communities showed a higher cover of CR and S species under panels than in inter-row or outside panels, according to the CSR model. Trait values and group abundance showed small differences between grazing and mowing but interactions of management and panel effects were significant in several cases indicating that management influences microhabitat effects. Our study demonstrated the strong filtering effects of solar panels on plant community traits. Long-term studies and in-situ trait measurements are needed to better understand solar park effects on plant communities.