Sharing the light, impact of solar parks on plant productivity, soil microbes and soil organic matter

Solar parks enable renewable energy production at a large scale, thereby reducing greenhouse gas emissions. However, the effects of this change in land use on vegeta tion and soil health are still largely unknown. In this study, we determined the impacts of solar parks on vegetation, soil biota and soil carbon between and below solar panels. We found lower plant and microbial biomass below the panels, while no differences in soil carbon pools were observed. The results stress the urgent need to design future solar parks that prevent soil degradation while still producing the renewable energy needed to combat climate change. Summary • Solar parks, large-scale arrays of photovoltaic panels, are a unique land use and play an important role in the renewable energy transition. However, the solar panels create shade and change the microclimate, potentially affecting plant growth and carbon inputs to the soil. These changes can influence key soil proper ties critical to long-term carbon storage and overall soil health. This study investi gated the impact of commercial solar parks on plant productivity and the colonisation of roots by mycorrhizal fungi, soil organic matter (SOM), soil microbial community biomass and composition and litter decomposition in 17 solar parks with contrasting shading levels across the Netherlands. • Soil samples and plant biomass samples were collected between and below the solar panels. The microclimate (temperature, moisture) was measured continuously over the growing season and cumulative solar irradiation during the growing sea son in relation to the solar panels was modelled. • Results show that above- and below-ground plant biomass as well as mycorrhizal colonisation were significantly lower below than between panels, while we did not find differences for SOM, carbon stocks and hot water extractable carbon. Plant productivity related negatively to the extent of light interception by the panels. Furthermore, fungal and bacterial biomass and the F:B ratio were lower below compared to between the panels while decomposition rates did not differ