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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

2013 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 support of Objective 1, ARS scientists mapped the distribution and abundance of Ludwigia hexapetala along 8 reaches of the Russian River, collected data on vegetation and environmental conditions, and analyzed sinuosity and river channel complexity. These ecological indices were used to evaluate changes in weed colonization, distribution and abundance and plant community structure. Studies continue to track phenological development and the dispersal of propagules from 4 reaches of the watershed. Plant fitness, seedling and mature plant density, survivorship, and seed rain in experimental plots were quantified to evaluate rare plant response to herbicide management of Lepidium latifolium. Seedling mortality of the endangered plants was very low (3-9%) among all treatments, and survivorship of mature plants was high (> 90%) in 2012. Seed production of endangered Chloropyron molle responded positively to herbicide treatment of L. latifolium. After the third year of management, herbicide treatments have had a positive influence on plant community composition, favoring native species and appropriate host plants for endangered parasitic plants. The fitness, distribution and abundance of the endangered plants have responded positively to weed management efforts. Demographic studies have been sufficient to document the positive effects of weed management on annual survival and fitness of the endangered plant populations, and alternative approaches to quantify responses to treatments. Ecophysiological studies on the influence of photoperiod on flower induction of yellow starthistle (YST) rosettes were conducted though growth chamber experiments completed in cooperation with NASA scientists at Moffit Field, California. These data were collected to support Objective 2, the development of predictive plant growth models. Additional field verification research on YST flowering was also conducted at study sites in Davis, California. Significant improvements have been made in understanding the environmental cues that induce flowering and seed production in YST. A combination of field growth assessments and laboratory growth and germination studies have been completed on the native species Zannichellia palustris, in areas where it competes with Eurasian watermilfoil. Temperature-dependent germination studies were conducted across a wide temperature spectrum and were used in a predictive model of germination and establishment times in natural areas. Only a portion of Objective 3 results were completed as two key scientists involved in this effort left the project. However, work on assessment of yellow starthistle water utilization across a wide environmental gradient was fully completed and was used to document environmental growth restrictions on plants in some geographic areas. These and other data are now being formulated into spatially explicit growth models to estimate geographically induced plant differences cause by such factors such as water availability, temperature regimes, and biological control agent synchrony and impact.

4. Accomplishments
1. Pepperweed management for ecosystem recovery. Pepperweed (Lepidium latifolium) invades tidal marshes, displaces endangered species and native vegetation, and undermines restoration efforts, therefore, ARS researchers at Davis, California, investigated effective pepperweed control methods for recovery of soft bird’s-beak, a federally-listed endangered plant. Spatial and temporal distribution/abundance of weed and rare plant populations, efficacy of weed control methods, effects on native vegetation and fitness responses of the rare plant were evaluated and Glyphosate applications were used to reduced weed density and biomass, while hand-weeding was not effective. Four years after treatment, pepperweed has been reduced by 83% with remaining stands reduced to low densities and the rare plant population has increased by 212%, number of population patches increased by 233%, and native vegetation has rebounded significantly. Results demonstrate careful herbicide management of pepperweed can have positive outcomes for sensitive habitat and species. ARS scientists used demographic analyses to project conservation needs in response to climate change, which is important as this area is the hub for most water deliveries is the Sacramento-San Joaquin Delta where a reliable water supply and restoration of the San Francisco Bay-Delta are legislated goals, thus Action Agencies are using these results as a model for improved weed management and endangered species recovery.

2. Algal control in Rice Production. In California’s water seeded rice systems algal/cyanobacterial biomass can be a problem during rice establishment as its growth may be stimulated by phosphorus (P) additions. Experiments evaluated the effects of fertilizer management on algal/cyanobacterial growth in rice fields, through two field-scale experiments the response of algal/cyanobacterial growth to surface, incorporated, and delayed P applications were evaluated. Effects of P application timing on algal/cyanobacterial biomass and rice yields were evaluated in enclosure experiments, giving results that indicate that higher levels of P increased algal/cyanobacteria biomass. Rice fields that received conventional surface applied P fertilizer had 4 to 8 times more algal/cyanobacterial biomass and 3 to 11 times higher concentrations of soluble reactive phosphate (SRP) than those in which P fertilizer was incorporated or delayed. Growth experiments with Nostoc spongiaeforme and water from the P incorporated fields and delayed P application fields indicate that water from these fields was P-limited for N. spongiaeforme growth, and that water from the surface applied fields was not P limited, thus delaying the application by up to 28 days but reduced algal/cyanobacterial biomass.

Review Publications
Grewell, B.J., Espeland, E.K., Fiedler, P.L. 2013. Sea change under climate change: case studies in rare plant conservation from the dynamic San Francisco Estuary. Botany. 91:309-318.

Ge, S., Xu, M., Anderson, G.L., Carruthers, R.I. 2007. Estimating leaf area index and aboveground biomass of an invasive weed (yellow starthistle, Centaurea solstitalis L.) using airborne hyperspectral data. Weed Science. 55:671-678.

Ge, S., Carruthers, R.I., Reddy, A.M., Gong, P. 2006. Texture analysis for mapping Tamarix parviflora using aerial photographs along the Cache Creek, California. International Journal of Remote Sensing. 114:65-83.

Deloach Jr, C.J., Carruthers, R.I. 2004. Saltcedar. In: Coombs, Clark, Piper and CoFrancesco, editors. Biological Control of Invasive Plants in the United States. Eugene, Oregon: Oregon State University Press. p. 311-316.

Ge, S., Carruthers, R.I., Spencer, D.F., Yu, Q. 2008. Canopy assessment of biochemical features by ground-based hyperspectral data for an invasive species, giant reed (Arundo donax). Environmental Monitoring and Assessment. 147:271-278.

Ge, S., Carruthers, R.I., Everitt, J.H., Kramer, M.G., Anderson, G.L. 2011. Multiple-level defoliation assessment with hyperspectral data: integration of continuum-removed absorptions and red edges. Environmental Monitoring and Assessment. 32(21):6407-6422. DOI:10.1080/01431161.2010.510492.

Pu, R., Gong, P., Yong, T., Xin, M., Carruthers, R.I., Anderson, G.L. 2007. Invasive species change detection using artificial neural networks and CASI hyperspectral imagery. International Journal of Remote Sensing. 140:15-32.

Fisher, A.J., Ditomaso, J.M., Gordon, T.R., Aegerter, B.J., Ayres, D.R. 2007. Salt marsh Claviceps purpurea in native and invaded Spartina marshes in Northern California. Plant Disease. 91:380-386.

Carruthers, R.I., Deloach Jr, C.J., Herr, J.C., Anderson, G.L., Knutseon, A.E. 2008. Saltcedar areawide pest management in the western United States. In: Areawide Pest Management: Theory and Implementation. Koul, Cuperus, Elliott, editors. Oxfordshire, United Kingdom: Council of Applied Biology International (CABI). p. 271-299.

Garren, J.M., Strauss, S.Y. 2009. Population-level compensation by an invasive thistle thwarts biological control from seed predators. Ecological Applications. 19:709-721.

Douhan, G.W., Smith, M.E., Huyrn, K.L., Westbrook, A., Beerli, P., Fisher, A.J. 2008. Multigene analysis suggests ecological speciation in the fungal pathogen Claviceps purpurea. Molecular Ecology. 17:2276-2286.

Last Modified: 05/29/2017
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