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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

2011 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. Formerly 5325-22000-021-00D (02/01/2011)


3.Progress Report
In this first experimental season, several field-oriented projects were initialized across multiple study locations. In these areas field plots were established, rare plants tagged, survivorship and density of seedlings and reproductively-mature rare plants evaluated, and biomass of desired and invasive plant species in experimental and monitored plots measured. Additional abiotic monitoring stations were set up and comprehensive assessments made of adjacent terrestrial and aquatic environments. Five key watershed study areas, including the Suisun Marsh, the Cache Creek drainage in the Capay Valley, the Fall River watershed, the Lake Tahoe Basin and portions of the Russian River drainage were instrumented as long-term study sites. Along the Russian River, data was collected on the phenological development and dispersal of Ludwigia hexapetala propagules from four discrete reaches of the watershed. In supporting greenhouse experiments, L. hexapetala capsules were subjected to float tests across salinity levels (fresh, brackish, sea water), followed by assessment of germination and viability rates. In the Suisun marsh, an unexpected establishment of a breeding population of endangered birds (California clapper rails) prohibited entry in some areas from March-August. Thus ARS worked with Fish and Wildlife Services (FWS) and rare plant research permit managers to implement adaptive management actions and modify the experimental design to allow the research to continue while avoiding potential impacts to the nesting birds. The modified experiment eliminated channel side plots, but we added additional plots in tidal marsh-upland ecotone areas across a bay shore to upper marsh estuarine gradient that, were not restricted. These areas allowed assessment of damage where invasive pepperweed has the most direct impact on the endangered plants. In the Fall River, 71 sample locations were established from the initiating springs of the river, along 35 km of reach that meanders through a major agricultural area. Comprehensive water quality and periodic biotic assessments on invasive Eurasian watermilfoil, native aquatic plants and associated insects were conducted to assess the effects of changing water conditions on associated flora and fauna of the waterway. Assessment of sedimentation and nutritional loading in the river adjacent to various cropping systems was assessed and related to invasive species growth and expansion in these areas. Methods of increased effluent management are being assessed to slow invasive species growth and improve agricultural compatibility with other natural resource management goals of the area. In addition, specific measurements on the rate of plant growth, water and nutrient uptake, photosynthesis and other factors are being assessed and used to evaluate beneficial and invasive plant competition in several of these study areas. This increased understanding is being used to enhance management options to help control invasive species on adjacent lands and in waterway operations.


4.Accomplishments
1. Yellow starthistle (YST) competition. Invasion of YST represents one of the most spectacular examples of biological invasion in the western United States, however the mechanisms leading to its success have not been clearly elucidated. While its success has been attributed to superior competitive ability, few studies have been performed to test this assertion, so ARS scientists from Davis, CA grew YST and wild oats in monocultures and mixtures to determine the strength of competitive interactions between these species. It was found that intraspecific competition exerted a greater influence over plant weight than did interspecific competition, and a companion study revealed temporal separation in the phenology of these plants explaining the weak role of interspecific competition. It was confirmed that water use patterns differed between these species, indicating niche partitioning, as wild oats reduced soil moisture only to a depth of approximately 150 cm, while YST depleted soil moisture to a depth of at least 270 cm. These patterns are important as it explains the mechanisms of plant and weed interactions in California rangelands. Since YST invasion of CA grasslands covers over 10 million acres, this is important in understanding where these plants can invade and how to help manage these habitats to exclude this weedy species.


Review Publications
Carruthers, R.I. 2011. Classical biological control of invasive species: fighting fire with fire. Outlooks on Pest Management. 22(3):122-128.

Westhuizen, L., Neser, S., Balciunas, J.K. 2010. Biology and host specificity of Diota rostra. African Entomology. 18(2):246-252.

Ge, S., Smith, R.G., Kramer, M.G., Carruthers, R.I., Jacovides, C.P. 2010. Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California. Journal of Theoretical and Applied Climatology. 105(1-2):107-118. DOI: 10.1007/s00704-010-0368-6.

Last Modified: 11/21/2014
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