Location: Invasive Species and Pollinator Health
Project Number: 2030-22000-029-24-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Apr 26, 2017
End Date: Mar 31, 2019
This agreement supports scientific research by ARS in partnership with California Department of Parks and Recreation Bay Area 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 Dept. of Parks & Recreation (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 patens, Apium graveolens, Iris pseudacorus) has increased. 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 determine the spatial and temporal distribution and abundance of primary invasive weed species, their relationship to the annual distribution and abundance of a resident endangered plant population, efficacy of management options for previously untreated weed species, and direct and indirect effects associated with management actions. Objectives are to 1) conduct annual assessment of the occupied area, distribution and abundance of 5 invasive weed species (perennial pepperweed, wild celery, black rush, salt meadow cordgrass, yellow flag iris) 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; 2) implement and evaluate a field experiment to test surfactant – herbicide combinations to identify treatment options that optimize efficacy for control of invasive black rush while minimizing undesirable non-target plant community responses; and 3) evaluate efficacy and plant community response of annual herbicide treatments by evaluating changes in distribution and abundance of multiple target weeds and plant community succession.
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 2017-2018 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: Conduct a field experiment to evaluate surfactants for efficacious treatment of black rush (Juncus gerardii). Approach: Experimental treatments randomly assigned will include 3 patch size classes reflecting differences in occupied area of established clones X 3 herbicide treatments (A: 2% Glyphosate + 1% Agridex; B: 2% Glyphosate + 2% Competitor; and C: Control) X 4 replicates for a total of 36 plots. Herbicide will be applied by DPR contractor. ARS will acquire and analyze pre- and post- treatment data. At peak summer growth, soil salinity and redox potential will be measured to assess variation in physical stress conditions among plots. Percent cover of live plant species will be determined by point intercept method in fixed 1-m2 quadrat frames, with quadrat subsamples increasing from 1 to 3 for the 3 size class plots. Differences among treatments will be analyzed using a repeated measures GLM statistical model for weed response to treatments. 3. Goal: Evaluate herbicide treatment efficacy and plant community response. Approach: Where invasive Spartina patens co-occurs with endangered plants, marked plots will be established, and density of the endangered plants and relative abundance of all live plant species present will be recorded before and 1 month after herbicide treatment. To assess efficacy of target weed treatments outside of rare plant protection zones, success will be evaluated 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 cover. To assess plant community dynamics, species composition will be measured in randomly assigned, replicated plots (10m X 4m) established in discrete microhabitat types. Plot measurements will include relative abundance, species richness, and origin (native, alien) of all plant species following weed treatment actions. Data will be analyzed with ANVOCA for repeated measures, and/or rank clock and rank abundance statistics.