Global energy needs drive major environmental changes by degrading ecosystems and increasing atmospheric carbon (C) emissions. Utility-scale solar energy (USSE, typically ≥ 1 MW, with ca. 2 hectares of land disturbance MW-1) is among renewable energy systems with the greatest potential to mitigate climate change. Although the contribution of solar energy to global power production grew ten-fold from 2008-2014, how land-based USSE photovoltaic (PV) arrays impact surface microclimatic features, biodiversity, and plant-soil interactions is essentially unknown. Regular spacing between PV array panels creates a heterogeneous shading and precipitation regime that may promote the formation of a novel patchy landscape and organismal gradient within the USSE array footprints. Quantifying the ecological consequences of PV arrays will help to identify synergies and trade-offs between energy generation, terrestrial conservation goals, and ecosystem impacts.
By regulating species coexistence and population persistence, habitat spatial heterogeneity is a critical regulator of biological communities. For example, spatial patterns of soil biota, and the biotic and abiotic factors that determine this patterning, will influence spatial patterns of decomposition dynamics and plant communities. Therefore, the heterogeneity created by the sitting of PV arrays is expected to have cascading impacts on plant-soil feedbacks through shifts in primary production and decomposition dynamics over the course of the 10-25 year lifespan of USSE arrays in a landscape. However, the development trajectory of landscape heterogeneity with array placement is uncertain. Using a set of three USSE PV arrays situated in fallowed farmland in southern VT, we tested the following questions: i) How do PV arrays impact surface and soil microclimatic conditions, and how do these effects vary seasonally? ii) Do altered abiotic conditions affect plant and soil decomposer community structures and functions? How do these changes impact higher trophic levels, including soil invertebrates? iii)How is soil organic matter content within the array footprint impacted by the competing effects of alterations to biotic and abiotic processes?
We found significant panel effects on ecosystem abiotic and biotic characteristics, but these effects varied seasonally and by site. The panels markedly affected soil temperature and moisture content. Panel presence also affected plant community composition, moisture, biomass, stoichiometry, and soil organic matter content, but no consistent effects on soil decomposer extracellular enzymatic activities or ground-dwelling invertebrate communities were detected. Scaled over space and time with the expansion of solar energy development, these effects may have implications for land management within the footprint of USSE PV arrays.