Location: Exotic and Invasive Weeds Research2011 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.
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 (C. mollis), a federally listed endangered tidal marsh plant that is directly impacted by perennial pepperweed (L. latifolium). In FY11, ARS scientists from Davis, California, tracked the phenological development of pepperweed to determine optimal time for herbicide applications. They assessed the distribution, abundance and habitat characteristics of pepperweed and soft bird’s-beak before and after annual weed management. In experimental plots, they collected live biomass and stem density data to evaluate efficacy of alternative management methods (hand spraying or hand wicking herbicides, and hand weeding). With FWS and preserve managers, ARS scientists from Davis, California, developed an adaptive management plan due to the unexpected establishment and nesting of endangered birds in FY11. Weed control actions and research elements were modified to avoid impacts while still accomplishing project objectives. In FY11, they tagged 336 rare plants in treatments with and without pepperweed or management, and with herbicide treatments to evaluate demographic responses and parameterize a model for management of endangered plant recovery.