Effects of habitat restoration and solar panels on soil properties and functions in solar parks

In the Mediterranean region, the construction of solar parks has strongly increased in order to replace fossil energy sources. However, the use of solar energy for electricity production requires large areas and impacts biodiversity and ecosystem functioning through soil degradation and vegetation destruction. Furthermore, solar panels change the microclimate hampering plant establishment and soil functioning. However, the specific effects of solar panels are still largely unknown. In our study, we tested different ecological restoration techniques (vermicompost addition, sowing of target species and seed material transfer from the reference community) to improve plant establishment and related soil functions. We further analyzed the effects of solar panels and interactions with these restoration techniques. A full factorial randomized block experiment was set up in a solar park in South-eastern France. Soil climatic, chemical (C and N content) and microbiological properties as well as the mesofauna (mites and springtails) were studied. The data were used to analyze trophic interaction networks of the soils. Vermicompost addition resulted in a strong increase in C and N content often used as criteria of chemical soil quality. Seed material transfer and sowing increased the diversity and abundance of the mesofauna and revealed more trophic interactions than the other treatments. Solar panels negatively affected most of the measured variables related to soil biodiversity and functioning. No interactions between the effects of solar panels and restoration treatments were detected for the soil properties. To improve the ecological restoration of soils under solar panels, more specific restoration methods need to be tested such as the use of soil engineer species.