Mycorrhizal fungi perform a variety of ecosystem services, including facilitating plant establishment and improving nutrient uptake by plants. However, little is known about which Southern Californian mycorrhizal fungi facilitate native plant biodiversity in grasslands invaded by Brassica nigra. To compare among restoration sites, soil samples were taken from intact native grasslands (>50% native), manually managed B. nigra plots (30–50% native) highly invaded B. nigra cover (<10–15% native), and introduced B. nigra experimental plots. We predict that B. nigra will inhibit arbuscular mycorrhizal (AMF) colonization of both native forb and grass roots and that introduced B. nigra plots will have the highest AMF community turnover between the dry and wet seasons. These soils were used to assay the AMF community by “baiting” the fungi with native grasses and forbs. After 45 days, the bioassays from each species and soil type were harvested. We extracted and morphotyped AMF spores from each host plant and soil type. Aboveground and belowground plant biomass and shoot height measurements were recorded. Plant roots were stained to assess AMF percent colonization in grass and forb roots. Comparisons among the extant AMF community across these experimental restoration sites were conducted by molecular analyses.
Results/Conclusions
Grass roots were significantly more colonized by AMF than forb roots. Across all treatments, Stipa pulchra roots were colonized by three times as many AMF than the forb Plantago erecta. In addition, S. pulchra produced significantly more above ground biomass than was produced by P. erecta. To date, our research shows that native grassland AMF are more capable of supporting native grass diversity than native grassland forb performance or diversity within this invaded Mediterranean ecosystem. Spores were extracted from all soil treatments and a high diversity of morphotypes was recorded. DNA has been extracted from roots, and comparisons made between restoration strategy, invasion status, and AMF community composition. Wet season monitoring indicates the presence of B. nigra in all experimental plots except the intact native grassland. However, additional samples from the upcoming dry season will enable a comparison between wet and dry season AMF community turnover. In addition, seasonal monitoring will inform future research into the role of these native AMF taxa in providing ecosystem services such as assisting plant establishment in inhospitable environments, drought tolerance, and grassland soil stabilization.