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United States Department of Agriculture

Agricultural Research Service


Location: Exotic and Invasive Weeds Research

2010 Annual Report

1a. Objectives (from AD-416)
1) Assess the marsh-wide abundance, distribution and habitat/community characteristics of invasive Lepidium latifolium and endangered Cordylanthus mollis ssp. mollis, before and after implementation of weed management control strategies. 2) Assess weed treatment efficacy, plant community succession, and non-target effects across environmental gradients within the marsh. 3) In pilot scale experiments, test alternative approaches for weed control in sensitive areas where invasive weeds directly interact with vulnerable endangered plants. 4) Conduct demographic-based research to evaluate weed response to management actions, and to diagnose causes of poor population performance of native plants, and provide biologically based data for integrated weed management strategies and endangered plant recovery.

1b. Approach (from AD-416)
• GPS technology will be used to record geospatial data on population size, distribution, and habitat conditions of target weeds and endangered plants at Southampton Bay Natural Preserve, Benicia, CA. Random control and treatment plots will be stratified within by discrete within-marsh hydrogeomorphic settings that correlate with observed phenological differences in Lepidium latifolium growth. Baseline evaluation will include evaluation of L. latifolium stem density, biomass and plant community associates, and sediment physico-chemical characteristics. Post-treatment evaluations will track changes in weed density, biomass and community succession to evaluate efficacy of management actions, and the need for adaptive change in approach. A life table response experiment (LTRE) will be conducted to evaluate weed demography and the direct response of soft bird’s-beak to Lepidium alternative weed control approaches. C. mollis ssp. mollis individuals in 0.25m-2 plots within Lepidium invaded subpopulations (treatment plots) will be tagged, and survivorship and life stage transitions will be recorded. At the end of the annual life cycle, fecundity of C. mollis will be quantified. Management option impacts on C. mollis population growth rates and survivorship will be compared. Results will be directly applicable to weed control strategies, conservation management, ecological restoration and endangered plant recovery efforts. Documents Reimbursable with DOi- Fish & Wildlife. Log 39319.

3. Progress Report
The agreement was established in support of Objective 1 of the in-house project, the goal being to develop effective weed control efforts that facilitate the recovery of soft bird’s-beak (Chloropyron molle), a federally listed endangered tidal marsh plant and its native plant community associates that are directly impacted by invasion of exotic perennial pepperweed (Lepidium latifolium) . We collected baseline data on pepperweed and rare plant distribution, abundance and demography and established rare plant protection zones prior to initiation of herbicide applications by California Dept of Parks & Recreation. We designed a life table response experiment to evaluate demographic response of the rare plants to weed management actions. We established 54 stratified-random plots that include 288 tagged rare plants, and evaluated seedling density and survivorship. To evaluate the efficacy of herbicide applications to pepperweed, repeated measures of live weed biomass, cover and non-target effects were evaluated from 24 plots stratified by inundation frequency. Seasonal measurements in field experiments and laboratory analyses of plant and environmental samples are in progress.

4. Accomplishments

Last Modified: 10/20/2017
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