Kataoka, Natalie Catherine2022-06-022022-06-022022-05https://hdl.handle.net/1794/2718221 pagesFor the past 200 years, non-native species have been anthropogenically introduced in California grasslands, reducing native species abundance and diversity. Trifolium hirtum is a non-native legume commonly used for cattle fodder and cover cropping because of its ability to fix nitrogen via bacterial symbionts. T. hirtum currently coexists with California native legume Trifolium willdenovii in established communities, however, T. hirtum has the potential to outcompete T. willdenovii under increased environmental stress, such as that caused by climate change. Considering how symbiotic rhizobia contribute to these Trifolium species’ ability to coexist or compete with other species, as well as how climate change alters these interactions, is essential for understanding potential impacts on native biodiversity and the response of important forage species to changing climate conditions. I tested 1) how rhizobial symbionts contributed to the survival and growth of a native and non-native legume species. 2) How drought influences the competitive relationships of the two legumes. And 3) how each species responded under interspecific and intraspecific competition. For both non-native T. hirtum and native T. willdenovii, I measured rhizobia nodule mass, seeded background count, weed species counts, and weighed the aboveground biomass of individuals grown under drought and ambient precipitation treatments. On average, there were no differences in the mass of nodules by species, however there was an observed a negative correlation between the biomass and nodule mass of uninoculated background T. willdenovii. Drought positively impacted the biomass of background T. hirtum individuals, however drought treatments negatively affected focal T. hirtum biomass compared to ambient precipitation. Drought had no significant effect on focal T. willdenovii biomass.enCreative Commons BY-NC-ND 4.0-USThesis / Dissertation