#49

Establishing Native Forbs in Medusahead Dominated Spaces

Stuart Schwab, University of California- Riverside, Department of Botany and Plant Sciences

Darrel Jenerette, UC Riverside, Department of Botany and Plant Sciences; Loralee Larios, UC Riverside, Department of Botany and Plant Sciences

Oak woodlands provide ecosystem services and habitat for many species. Unfortunately, invasive plant species disrupt these habitats and services, reducing plant biodiversity and altering soil microbial communities. Medusahead (Taenitherium caput-medusaea) is one such invasive, reducing forage quality, biodiversity, and increasing fire risks. Medusahead management strategies have been developed to reduce its cover and spread; however, long term success requires establishing another plant community that can initiate return of previous ecosystem services and repel re-invasion. Establishing a native plant community in invaded areas is often hindered by the effects the invader has had on its surroundings, including the accumulation of litter, lack of soil symbionts that native plants are dependent upon, and reductions in native seed availability. We investigated why native species fail to establish focusing on three key mechanisms: inhibition by medusahead litter, lack of soil microbial symbionts, and native seed availability. These mechanisms can hinder the establishment of herbs and other understory vegetation that are compatible with efforts to restore oak woodland vegetation. To assess the importance of these mechanisms in preventing native species establishment, we performed a field experiment at the Sierra Foothills Research Extension Center north of Sacramento, CA. We used plots where litter had been removed, added a commercial inoculant to assess the effects of soil symbionts, and selected four seed mixes focused on early, mid, and late seasonality of native seeds. We collected species composition in 40 plots, for five replicates per treatment, twice during the growing season. Litter removal (ANOVA p<0.0001), and commercial inoculant addition (ANOVA p=0.0027) both reduced medusahead cover. Seeding with inoculant increased diversity (ANOVA p=0.03). Our findings suggest medusahead cover may be reduced through litter removal and inoculations, and that the establishment of a more desirable community may be enhanced through including inoculant with seeding efforts. In our presentation, we will discuss how our research results can be applied to oak woodland restoration projects that strive to restore and enhance historical oak woodland conditions. Addressing the causes of failed native plant establishment driven by invasive species may yield returns in lost ecosystem services and increases in functional habitat.