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United States Department of Agriculture

Agricultural Research Service

Research Project: Landscape-Level Assessment and Management of Invasive Weeds and Their Impacts in Agricultural and Natural Systems

Location: Exotic and Invasive Weeds Research

2012 Annual Report

1a.Objectives (from AD-416):
Objective 1: Determine invasive weed species growth, development, reproduction, population dynamics and spread across complex landscapes. Objective 2: Develop predictive models of invasive species interactions at population, community and landscape scales, addressing interactions with other species, variation of biological responses to physical processes, and resultant impacts on ecosystem function. Objective 3: For weeds such as yellow starthistle, pennywort, saltcedar, Eurasian watermilfoil, Brazilian waterweed, curlyleaf pondweed, giant reed, water primrose, and water hyacinth, develop adaptive management models using remote sensing products, spatially explicit biological data and other tools to aid in assessing the impact and management of invasive species on natural resources, ecological processes, and forage production and quality. Objective 4: Integrate landscape ecology into decision support and assessment tools for farmers, ranchers and land/water resource managers.

1b.Approach (from AD-416):
To address this research area we propose to partner with other research groups specializing in spatial technology (e.g. NASA-Ames) to develop a better understanding of large-scale weed invasions and related ecological issues. Such an effort is expected to provide new methods to improve management of these problems at the spatial scales necessary to develop economic and sustainable land use practices that optimize overall ecosystem processes. In parallel with these approaches, we also see an increasing overlap of agriculture, urban and natural area activities that often affect one another, with little thought given to developing management technologies that address wider resource management goals. The research proposed in this project aims to begin assessing the invasive species crisis and these wider interacting issues, by linking conventional weed science approaches with new ecosystem management tools through partnerships between USDA-ARS, NASA and appropriate university colleagues. Although the funds specified in this project are exclusively USDA-ARS funds, supporting ARS scientists, the proposal itself has been written jointly with colleagues from different agencies as direct collaborators to provide a holistic melding of basic biological research with landscape level tools such as area-wide remote sensing, spatial characterization of environmental heterogeneity and synthesis of ecological understanding through area-wide data collection and modeling. Specific tools such as satellite and aerial-based remote sensing, parallel processing computing and network-based environmental prediction will form the basis of jointly planed and implemented studies. This work will have the goal of shedding new light on invasive species management in the context of wider scope issues, such as overall integrated vegetation and natural resources management, while facilitating sustainable ecosystem processes. Thus our goal is to develop, apply, assess and make available new landscape level tools for the management of agricultural, natural and urban ecosystems, as they relate to invasive plant management and related activities in representative western watersheds.

3.Progress Report:
Substantial progress was made towards evaluation of variation in dispersal phenology, propagule deposition and dormancy traits that influence colonization of Ludwigia hexapetala and plant community composition. ARS scientists worked cooperatively with Sonoma County Water Agency biologists to expand field research sites in the Laguna de Santa Rosa tributary and in the upper, middle, and lower mainstem reaches of the Russian River watershed. Data collection was initiated to assess vegetation, river channel complexity, and other environmental variables to explain variation in Ludwigia hexapetala abundance and elucidate environmental conditions associated with successful colonization and the impact of the weed invasion. Field data collection was repeated in 2012 on the spatial variation in phenological development and dispersal of L. hexapetala propagules, and greenhouse trails on the buoyancy and viability of seed capsules was completed. Field monitoring and assessment yellow starthistle growth and development has been completed across multiple wide-area landscapes and is being evaluated to assess this weed’s growth and development under differing ecological conditions. Additionally, the growth, development and reproduction of both yellow starthistle and cheatgrass are being studied in controlled environments at the NASA Ames laboratory. Various studies are either underway or have already been completed along with preliminary studies on competitive interactions of these species under limiting nutrient conditions and when exposed to naturally produced root exudates. Population models are being used to synthesize key biological data and make predictions on invasive species growth and invasion potential, including the aquatic weed Eurasian watermilfoil that is infesting the Fall River in Northern California. These modeling efforts have shown greater potential for specific invasions which may further be affected by global climate change. Demographic models are also being used to support the California Department of Parks & Recreation weed management and wetland restoration objectives, and the US Fish & Wildlife Service Endangered Species Act recovery actions. ARS scientists evaluated the efficacy of management actions to control invasive Lepidium latifolium (perennial pepperweed) in critical habitat occupied by an endangered plant in the San Francisco Estuary, and evaluated the endangered plant’s response to various management actions. Additionally, 144 rare plants within a field experiment were evaluated for life stage transitions, survivorship and fecundity to parameterize a model to assess demographic responses of endangered plants to active management of invasive Lepidium latifolium. Existing models of yellow starthistle and several of its natural enemies were also evaluated over large landscapes to assess the magnitude and variability of growth responses and herbivory over wide-areas. This effort involved the use of both solar radiation models and temperature profiles across varying terrain to realistically implement these studies.

1. Lepidium latifolium management research. This research was conducted to facilitate the recovery of soft bird’s beak (Chloropyron molle subsp. molle), a federally listed endangered tidal marsh plant. Prior to initiation of herbicide applications, ARS scientists determined the size, abundance, and distribution of both the invasive weed and the rare plant populations. After two years of treatment, the occupied area of the invasive weed has been reduced by 11.8%, and 71% of the originally invaded area has been reduced from nearly 100% to <30% cover of the weed. After 3 years of precision herbicides treatments to the target weed, endangered soft bird’s-beak increased 211% compared to the baseline assessment. Results of studies to evaluate the demographic responses of the rare plants to invasive weed management suggest weed control improves survivorship and fecundity of the endangered plant species. This project further demonstrated that precision application of herbicides can proceed with positive outcomes for native plant communities, and is being used as a model by US Fish and Wildlife Service for endangered plant recovery actions.

Review Publications
Carruthers, R.I., Franc, M.K., Gee, W.S., Cosse, A.A., Grewell, B.J., Beck, J.J. 2011. Volatiles emissions from the flea beetle Altica litigata (Coleoptera: Chrysomelidae) associated with invasive Ludwigia hexapetala. Chemoecology. 21(4):253-259.

Cabrera Walsh, G., Dalto, Y., Mattioli, F., Carruthers, R.I., Anderson, L.W. 2013. Biology and ecology of Brazilian elodea (Egeria densa) and its specific herbivore Hydrellia sp in Argentina. Biocontrol. DOI 10.1007/s10526-012-9475-x.

Reddy, A.M., Carruthers, R.I., Mills, N.J. 2012. Integrated management of Scotch broom (Cytisus scoparius) using biological control. Journal of Invasive Plant Science and Management. 5(1):69-82. DOI: 10.1614/IPSM-D-11-00048.1.

Last Modified: 4/19/2014
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