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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Research Project #437527

Research Project: Assessment of Plant Species Invasions to Guide Adaptive Weed Management for Endangered Plant and Tidal Wetland Recovery

Location: Invasive Species and Pollinator Health

Project Number: 2030-22300-032-012-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Feb 1, 2020
End Date: May 14, 2022

This agreement supports scientific research by ARS in partnership with California Department of Parks and Recreation Diablo Range District to optimize comprehensive weed management approaches for tidal wetland and endangered plant population recovery at Southampton Bay Wetland Natural Reserve in the San Francisco Estuary. A previous, related agreement between California Department of Parks & Recreation Bay Area District (DPR) and ARS scientists focused on evaluation of the efficacy of herbicide management targeting invasive perennial pepperweed (Lepidium latifolium) and response of the weed and an endangered plant community to management actions. In a five-year effort, perennial pepperweed was reduced by 85%, resulting in positive growth responses of the endangered plant population. However, the dominance and spread of secondary invasive species (Juncus gerardii, Spartina spp., Apium graveolens, Iris pseudacorus, Symphyotrichum subulatum var squamaturm) challenges habitat enhancement goals. The purpose of this new agreement is to evaluate comprehensive weed management actions for endangered plant conservation and native tidal wetland plant community recovery. Specifically, ARS scientists will alert Park managers to new invasions, determine the spatial and temporal distribution and abundance of six invasive weed species, their relationship to the annual distribution and abundance of a resident endangered plant population, efficacy of cooperator management actions, including direct and indirect effects on target weeds and desirable plant species. Objectives are to 1) conduct annual assessment of the occupied area, distribution and abundance of the 6 invasive weed species and endangered soft bird’s-beak plant populations in the Preserve to delineate stratified management zones for species-specific treatments and endangered species protection zones; and 2) quantitatively evaluate efficacy and plant community response of annual herbicide and/or alternative treatment methods by evaluating changes in distribution and abundance of multiple target weeds and host plant community supporting rare plant populations.

1. Goal: Acquire spatially explicit data to delineate zones for weed management approaches relative to occupied habitat type and proximity to occupied area of endangered plant species. Approach: Annual population censuses will be conducted during 2020-2021 at appropriate phenological stages of target species. Geospatial data will be recorded with GPS units to determine the distribution and occupied area of target weed species and the endangered plant population. Presence of unexpected, new alien species will be documented. Cover classes (trace, low, medium, high) of weed-occupied patches, and exponential cover classes of the endangered plants will be recorded along with data on associated plant community and habitat conditions. GIS-based maps will be prepared showing distribution and cover classes of target weeds and endangered plants. Protection zones based on proximity of endangered species to target weeds for stratified approaches to herbicide applications will be delineated on maps. 2. Goal: Evaluate herbicide and integrated treatment efficacy and plant community response. Approach: Herbicide and other management applications will be directed by DPR staff and implemented by their contractors. To assess efficacy of target weed treatments outside of rare plant protection zones, the ARS team will evaluate success by comparing marsh-wide distribution and abundance of the select target weeds before and after annual treatments using GPS-acquired data and analysis of changes in live occupied-area and species cover.