Effects of simulated solar arrays on seed dynamics in California desert plant species
Physical and Biological Sciences
Ecology and Evolutionary Biology Senior Thesis
Seed dormancy is an important bet-hedging strategy for annual species in variable environments, allowing persistence through unfavorable periods. Desert annual species are known for complex seed dynamics, with germination and dormancy influenced by environmental factors including soil moisture, temperature, and light availability. These same factors also affect soil microbes, and can stimulate activity of fungal pathogens affecting seed survival in the soil seed bank. Naturally occurring interactions between desert annual seeds and soil microbes may be affected by a renewable energy boom in California’s desert, where large facilities alter natural shade and moisture patterns. If belowground effects differ among species, it could influence seedling emergence aboveground, and ultimately community composition at energy sites. To test whether these shifts in abiotic regimes affect seed dormancy, seed survival, and soil microbial activity, we used experimental panels to alter natural shade and moisture patterns. We asked how treatments affect seed germination rates and seed bank survival for a native annual species pair, one common and one rare. We also tested treatment effect on a widespread, noxious invader of the desert southwest. We found that seed germination was not affected by microhabitats created by experimental panels, or by fungicide treatment intended to reduce soil pathogen activity. We then divided apparently dormant seed between experiments testing for survival and pathogen infection. Microhabitat and fungicide affected seed survival only in the rare endemic. Microhabitat only affected fungal growth on plated invader seed, with higher growth on seed from the shade microhabitat; fungicide treatment did not affect fungal growth for any species. Regardless of microhabitat and fungicide treatment, we observed striking differences in germination across species, with a much higher proportion of seeds germinating for the invader and rare species compared to the common species.
