Abstract
The introduction of invasive plant species has devastated many ecosystems worldwide and led to biodiversity declines. Management and restoration of invaded landscapes costs millions each year with varying levels of success. There are currently many weed management approaches; however, research has shown that relying on single approaches will not control multi-species invasions. Integrated pest management (IPM) focuses on sustainable land management practices to control and prevent a variety of invasive species using a combination of different approaches. In seasonal wetlands like vernal pools, invasive plants alter plant community composition and destabilize hydroregimes, preventing inundation dependent plants and wildlife from establishing. This study evaluated the effects of combining three common weed management approaches, grazing, mowing, and herbicide, on plant community composition, and native and invasive plant cover and richness at the Yolo Bypass Wildlife Area, Sacramento Valley of California, USA. Two major questions investigated were (1) how does the addition of mowing and herbicide influence fall grazing, and (2) how implementation of an IPM approach impacts the current invasive dominated plant community composition. Treatments are defined as grazing alone (G), grazing+mowing (GM), grazing+herbicide (GH), and grazing+herbicide+mowing (GHM). GH and GHM treatments reduced invasive cover by over 95%, while increasing native cover by over 200%. GM treatments reduced invasive cover by 81% and increased native cover by 89%. G alone reduced invasive cover by only 37% and increased native cover by 87%. Reduction of invasive cover resulted in a plant community composition that favored native plants. These results suggest that utilizing an IPM approach will greatly reduce invasive cover compared to fall grazing alone. Encompassing multiple different invasive species can also have a positive effect on native species establishment, and shift plant community composition from invasive-dominated to native-dominated. Combinations of GHM successfully targeted invasive grasses and forbs, resulting in an increase of native forb abundance. Additionally, this study provides justification for incorporating IPM into current land management plans for areas that are dominated by invasive plants.