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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Research Project #443598

Research Project: Invasive Plant Management Strategies for Endangered Plant Recovery and Tidal Wetland Restoration under Changing Environmental Conditions

Location: Invasive Species and Pollinator Health

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

Start Date: Mar 23, 2023
End Date: Dec 14, 2024

This agreement supports scientific research in partnership with the Cooperator to develop and optimize comprehensive weed management approaches for tidal wetland and endangered plant population recovery at Southampton Bay Wetland Natural Preserve at Benicia State Recreation Area in the San Francisco Estuary. A previous, related agreement with the Cooperator focused on evaluation of the efficacy of herbicide management of invasive perennial pepperweed (Lepidium latifolium) and response of soft bird’s-beak (Chloropyron molle), an endangered hemiparasitic plant dependent on a supporting native host plant community, to weed management actions. Pepperweed was successfully reduced to trace levels, and focus shifted to guide adaptive management to curtail the spread of six secondary invasive weed species in the wetland to support recovery of the endangered plants, and endangered bird populations that have begun to re-establish in the marsh. Cooperators have identified a need for continued research support to address long-term outcomes with ecological succession, and emerging management challenges in the context of changing environmental conditions, including new weed invasions and sea level rise. 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 spatial-specific treatments to protect and enhance habitat for endangered plant and bird species; and report detections of new invasive plant species to facilitate rapid management response; and 2) Quantitatively evaluate efficacy and plant community response of annual herbicide and cultural integrated weed management methods specific to each target weed species through marsh-wide assessment of pre- and post- treatment changes in the distribution and abundance of target weeds, endangered plants, and the native host plant community. Assist Cooperator if needed/feasible, with design and implementation of pilot-scale tests of integrated methods for improved efficacy in changing environments.

1. Marsh-wide surveys will be conducted to 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. Where/when marsh entry is permitted, two annual population censuses will be conducted at appropriate phenological stages of target weed and focal endangered plant species. Geospatial data will be recorded with GPS units to determine the distribution and occupied area of all focal populations. 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. Presence, distribution and abundance of unexpected, new alien species will be documented. GIS-based maps will be prepared showing distribution and cover classes of target weeds, new invasive weeds, and endangered plants. Occupied area of all studied taxa will be determined, and frequency of plant associates in the rare plant host community will be quantified. Rare plant protection zones based on proximity of endangered species to target weeds for stratified management approaches will be established. Plant community composition of occupied patches of rare plants will be analyzed. Maps and analyses will be provided to the Cooperator. 2. Assessment of herbicide and integrated treatment efficacy and plant community response will be conducted during two annual treatment seasons. Foliar herbicide spay applications outside of rare plant protection zones will be implemented by the Cooperator and/or their pesticide applicators with assisted entry guided by project ornithologist contractors. In 2023, management treatments to weeds within 1-meter of rare plant stands will be hand-applied in experimental plots by qualified scientists. To assess efficacy of marsh-wide target weed treatments, 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. If feasible, new integrated management methods for control of black rush (Juncus gerardii) designed to avoid impacts to rare plant seedlings will be experimentally-implemented and evaluated. 3. The Cooperator will be alerted to potential risks posed by newly detected alien plant species, and rapid response management options will be discussed in project management team meetings.