COS 109-7
Changes to shade and water regimes imposed by solar development affect desert plant performance and community attributes

Thursday, August 14, 2014: 3:40 PM
302/303, Sacramento Convention Center
Karen E. Tanner, University of California, Santa Cruz, Davis, CA
Kara A. Moore, Evolution and Ecology, University of California, Davis, Davis, CA
Bruce M. Pavlik, Restoration Ecology, Royal Botanic Gardens, Kew, United Kingdom

California aims to generate 33% of its electrical power from renewable sources by 2020, spurring large-scale solar development in the state’s desert regions. Changes to shade and water regimes imposed by solar installations may directly or indirectly affect desert plant communities and the density, growth, and fecundity of individual species. Our four-year study employs an experimental approach to these questions, deploying shade panels in desert annual communities and monitoring community and plant response. We compare the performance of annual sunflowers Eriophyllum mohavense (rare) and E. wallacei (common) under the panels, where they are shaded and receive limited rainfall, and in control plots where they receive natural light and rain. We measure performance by tallying the number of individuals of each species, their size, and their seed production. We also measure and compare annual community richness, diversity, and evenness in shade and control plots.


Despite the inherent variability in seasonal performance of desert annual plants, we’ve found clear effects of experimental shading on E. wallacei and its community. Under panels, photosynthetically active radiation is reduced by approximately 85%, and afternoon soil temperatures are on average 11º C cooler. These conditions represent a strong departure from the natural regime that is reflected in species and community response. Density of E. wallacei was lower in shaded plots, suggesting that shade suppressed emergence from the seed bank. In 2013, significantly more plants died before flowering under shade panels, which means that average seed production per plot was reduced in shaded plots. We also found that species richness (the number of different species present) and community abundance (the number of individual plants present) was reduced by panel shade. By taking a rare experimental approach to exploring the effects of solar panels, this work provides insight that can be used by public land agencies as they consider impacts of solar development on rare desert plants and their communities.