Invasive plants have the potential to drastically alter the structure of plant communities in a diversity of ecosystems. The effect of these invasions on native soil remains understudied, and learning more about the soil-mediated impacts of invasions could improve efforts to restore threatened systems. Here, I aimed to determine whether an invasive grass changes soil through abiotic or biotic pathways, and whether these changes reduce native plant growth. Ehrharta erecta, a perennial grass native to South Africa, has invaded 14 counties in California and has been shown to outcompete native plants. To examine how E. erecta impacts soil, I used a soil-conditioning experiment in two distinct phases. In the first phase, I planted 3 native species and E. erecta in both sterile and nonsterile potting soil that had been conditioned by E. erecta. To directly examine impacts of E. erecta on native plants under natural biotic conditions, I performed a second phase using soil collected from the field. In this second phase I planted 3 native species and E. erecta in field soil conditioned by natives and field soil conditioned by E. erecta. During both phases, I measured three aspects of plant health of all species after each stage of growth. I measured growth rate, including leaf area, height, and biomass; soil fertility, including electric conductivity, pH, inorganic nitrogen content, and phosphate content; and percent mycorrhizal colonization.
Results/Conclusions
Preliminary results indicate that E. erecta grows more poorly in soil that has been conditioned by E. erecta itself; an effect which is especially pronounced in sterilized soil. This could indicate a buildup of pathogens in soil where E. erecta has grown, and that restoration efforts should be focused on areas that are not yet fully invaded. Further results from this study will produce more detailed insight into these interactions. These findings will provide knowledge that is important to the conservation of native biodiversity throughout California and to invasion ecology as a whole.