Evaluating integrated pest management effects on seasonal wetland plant communities

Introduction of invasive plant species has devastated many ecosystems worldwide and led to biodiversity declines. In seasonal wetlands, invasive plants alter community composition, destabilize hydro‐regimes and prevent native species establishment. While there are currently many management approaches, plant functional groups respond differently to each based on phenology and taxonomy. Research has shown that single approaches will not control multi‐species invasions, which is a common occurrence in Mediterranean seasonal wetlands and grasslands. Integrated pest management (IPM) focuses on sustainable land management practices to limit diverse invasive species using a combination of different approaches.

Implementing an IPM approach, this study tested whether combinations of herbicide and mowing, with fall grazing, affected native and invasive plant community composition, cover and richness. We assessed this over 2 years at the Yolo Bypass Wildlife Area, California, USA.

We found that treatments with two or more combined IPM approaches decreased invasive plant cover and richness and promoted a native plant dominated community. However, treatment effects for invasive plant richness and cover did not carry over into the second year and invasive plants re‐established. These results suggest that an IPM approach can greatly reduce invasive cover; however, annual management is needed to sustain native communities.

Synthesis and applications : Our results show that annual invasive plant management is needed to recover and promote native communities. The timing and seasonality of treatment application is also important in determining management success. While fall grazing is conducted annually, this site greatly benefited from the implementation of IPM in the spring to capture plants at vulnerable phenological stages. Using two additional methods (i.e. herbicide and mowing), multiple functional groups were targeted to prevent secondary invasions. These findings provide insight into how management priorities should shift to focus on the depletion of invasive seed banks and prevent reestablishment in areas with multi‐species invasions to promote native plant establishment.