Location: Great Basin Rangelands Research
2023 Annual Report
Objectives
The Great Basin covers approximately 54 million hectares of the western United States with ranching, mining, and recreation as the primary economic activities. Invasive annual grasses and expanding native conifer populations have significantly altered ecosystems on over 20% of the Great Basin. Changes in plant type and cover, together with climate variability, drought, and land conversion have resulted in dramatic reductions in available forage and wildlife habitat, while increasing the frequency and intensity of wildfires. Public awareness of the impacts of invasive weeds has produced conflicts regarding proper rangeland management strategies. The research proposed here will produce critical data regarding the development of complementary control strategies to address 1) biological, chemical, and cultural control of the most important invasive annual grass species: cheatgrass (Anisantha tectorum), red brome (A. rubens), and medusahead (Taeniatherum caput-medusae); and 2) the effects of woodland encroachment on water resource availability. Research will focus on the discovery and evaluation of arthropods as biological control agents against invasive annual grasses; development of methods to revegetate rangelands degraded by wildfire with plant species that can prevent reinvasion of annual grasses and other noxious weeds, while enhancing biological diversity and forage for grazing animals; and assessment of water use by native conifer populations that are replacing grazable range. Resulting management guidelines and tools will facilitate sustainable delivery of goods and services from Great Basin ecosystems to agricultural producers and land managers, while mitigating the deleterious effects of weeds and wildfires.
Objective 1: Discover and evaluate new biological control candidates for invasive annual grasses i.e., medusahead, cheatgrass, and red brome to develop new biological control strategies. [NP304, C2, PS2B]
· Sub-objective 1A: Conduct field surveys to discover, identify, and collect natural enemies of medusahead, cheatgrass, and red brome.
· Sub-objective 1B: Evaluate candidate biological control agents of medusahead, cheatgrass, and red brome for their suitability for release in the Great Basin and adjacent invaded regions.
Objective 2: Analyze the distribution of limited resources critical for plant growth between native and invasive plants, soil properties, and hydrologic processes on degraded rangelands to improve rangeland conservation and rehabilitation strategies. [NP304, C2, PS2B]
· Sub-objective 2A: Assess the effects of pre- and post-emergent herbicides on invasive cheatgrass populations and on the rehabilitation of ecosystems after wildfire.
· Sub-objective 2B: Investigate and quantify critical water resources of rangelands, including water use of pinyon and juniper and hydrologic responses of a meadow to tree control.
Approach
Foreign surveys for natural enemies of medusahead, red brome and cheatgrass in their native ranges will be conducted by a team of collaborators led by ARS-Reno, in coordination with European and other ARS partners. Efforts will be made to visit each surveyed target weed population at least once in all seasons over the course of the project in order to observe all plant phenological stages and their associated natural enemies. New natural enemies of targeted annual grass species that are discovered in the course of these surveys will be prepared for evaluation as candidate biocontrol agents (CBCAs), including testing of host-range and the potential for each CBCA to reduce target weed populations. Target weed populations will also be surveyed in the Great Basin to determine if native-range natural enemies are already present. Genetic markers will be used to reveal precise relationships between geographically separated populations of CBCAs.
The efficacy of three soil-active pre-emergent herbicides, Imazapic (Plateau), Sulfometuron methyl-Chlorsulfuron (Landmark XP), and Indaziflam (Esplanade), to reduce cheatgrass and its associated seed bank will be tested. Herbicides will be applied in the fall on two recently-burned Wyoming-sagebrush sites, as well as on adjacent unburned areas infested with cheatgrass. Seed mixes (native and introduced species) will also be evaluated for their ability re-establish persistent, desirable plant communities. A weather will be established station at each research site to record amount and time of precipitation events. Plant and soil attributes will be measured bi-monthly over the entire year. Foliar cover, seedling emergence, mortality, persistence, and density of all test plant species, as well as cheatgrass seed bank density, will be estimated and species diversity and richness will be calculated. Effects of herbicides and seeding treatments on native plants, invasive species, biological soil crust, and soil properties will be evaluated.
Pinyon and juniper trees will be instrumented with heat dissipation probes to measure transpiration at Porter Canyon Experimental Watershed (PCEW) in plant communities dominated by pinyon-juniper, sagebrush steppe, and meadows (where groundwater springs occur). Locations will include a valley bottom site and east- and west-facing hill slopes. Additional trees will be instrumented with variable depth probes to control for reductions in flow with depth of xylem area. Stems will be collected from trees to extract xylem water to determine the source of transpiration water from these trees using stable isotopic analyses of hydrogen and oxygen in plant xylem water. In addition, the effects of mechanical tree removal on a downslope meadow system will be quantified by measuring changes in ephemeral flow and groundwater levels relative to eight years of baseline data. Vegetation transects will be measured annually to quantify tree removal treatments on groundwater depth, soil, moisture, meadow community composition, and peak of seasonal greenness
Progress Report
This report documents fiscal year (FY) 2023 progress for project 2060-22000-025-000D, titled, “Development of Ecological Strategies for Invasive Plant Management and Rehabilitation of Western Rangelands”.
ARS researchers in Reno, Nevada, made significant progress in support of Sub-objective 2A, Experiment 2A1, where repeated years of herbicide and seeding applications were performed to test three separate pre-emergent herbicides for their efficacy on cheatgrass control. The aim of the cheatgrass control is to reduce competition making soil resources more available and improve the ability of targeted seeded species to germinate and establish. Soil samples continued to be collected and reveal significant increases of soil moisture and available nitrogen after cheatgrass control, nearly doubling soil moisture and sometimes increasing available nitrogen more than 10-fold. Bioassay samples were collected to monitor cheatgrass seed bank densities, which have been significantly reduced due to the efficacy of pre-emergent herbicides to reduce cheatgrass above-ground densities and seed production prior to seeding efforts. By monitoring seeded species establishment densities, researchers have observed not only increased establishment, but also perennial seedling establishment where none has occurred in untreated (non-herbicide) plots. Although the region experienced drought conditions in previous years, this past year resulted in very favorable precipitation resulting in higher survivability of seeded perennial grasses. ARS researchers have observed that adequate establishment densities of perennial grasses lead to a decrease of cheatgrass densities and associated fuels through competitive exclusion by perennial grasses. By increasing available soil resources with effective weed control treatments perennial grasses can be successfully established and result in reduced wildfire threats, increased sustainable grazing resources and improved wildlife habitats. Preliminary data was presented at international, regional, and state meetings as well as stakeholder field tours.
In support of Subobjective 2A, Experiment 2A2, ARS researchers evaluated the use of herbicide and seeding treatments after wildfire. Two common post-fire rehabilitation treatments in areas prone to annual grass invasion include herbicide application and subsequent seeding with perennial species. Although this is common practice, there is a lack knowledge on how these combined treatments affect plant communities and soil properties. Researchers established an experiment at the Strawberry fire site near Great Basin National Park, in collaboration with the Bureau of Land Management and the National Park Service, to assess the effects of herbicide and seeding treatments. In a factorial design, ARS researchers applied two herbicide treatments, three native seeding treatments at two seeding rates. Unburned plots were also established outside the fire perimeter as a control. Plant cover, plant height, gap intercept, and biological soil crust cover were measured at peak growing season. To characterize the soil physical environment, researchers continued to monitor soil moisture and temperature using probes, and measured soil stability and soil surface roughness. The methods portion of the manuscript has been written and an additional year of data has been added for analyses.
In support of Sub-objective 2B and subordinate project #2060-22000-025-06I, weed challenges in the Great Basin are not limited to exotic or annual species. Since the 1850s, native conifers (juniper and pinyon) have been infilling existing woodlands and expanding into sagebrush steppe. Efforts to reduce woody plant encroachment have been undertaken by multiple land management agencies and private producers who are concerned with the reduction in forage for domestic grazing, increased wildfire risk, increased soil erosion, and a reduction in water availability for desirable plant communities. At the Porter Canyon Experimental Watershed in Nevada, ARS researchers completed multiple experiments, and long-term instrumentation was used, to examine the ecosystem effects of tree control treatments. An additional year of data was added on the responses of meadow groundwater levels and meadow soil moisture to the removal of pinyon and juniper.
The specific goal of Sub-objective 2B1 was to quantify the amount water used by the dominant encroaching woody species of the Great Basin; these species are pinyon and juniper. Eight years of data were collected from 31 pinyon and 15 juniper trees instrumented with heat dissipation probes to measure tree sap flow velocity and the total volume of water used by these species. These data were reduced to six years of data, that had nearly continuous data for full calendar years and water years. Daily and hourly data was processed with applied conditional filters to reduce noise from electrical malfunctions (e.g., low battery voltage, random noise), periods when the mean daily temperature was less than 0°C (Celsius), days with incomplete periods of record, and days where the filtered data by species was less than five individual trees. These data have been summarized at the individual tree level and scaled to water use at the stand-level. A poster was completed and presented at the 2023 Ecological Society of America Annual Meeting in August of 2023.
Accomplishments
Review Publications
Hoover, D.L., Abendroth, L.J., Browning, D.M., Saha, A., Snyder, K.A., Wagle, P., Witthaus, L.M., Baffaut, C., Biederman, J.A., Bosch, D.D., Bracho, R., Busch, D., Clark, P., Ellsworth, P.Z., Fay, P.A., Flerchinger, G.N., Kearney, S.P., Levers, L.R., Saliendra, N.Z., Schmer, M.R., Schomberg, H.H., Scott, R.L. 2022. Indicators of water use efficiency across diverse agroecosystems and spatiotemporal scales. Science of the Total Environment. 864. Article e160992. https://doi.org/10.1016/j.scitotenv.2022.160992.
Snyder, K.A., Robinson, S.A., Schmidt, S., Hultine, K.R. 2022. Stable isotope approaches and opportunities for improving plant conservation. Conservation Physiology. 10(1). Article coac056. https://doi.org/10.1093/conphys/coac056.
Young, S.L., Archer, D.W., Blumenthal, D.M., Boyd, C.S., Clark, P., Clements, D.D., Davies, K.W., Derner, J.D., Gaskin, J.F., Hamerlynck, E.P., Hardegree, S.P., Jensen, K.B., Monaco, T.A., Newingham, B.A., Pierson Jr, F.B., Rector, B.G., Sheley, R.L., Toledo, D.N., Vermeire, L.T., Wonkka, C.L. 2023. Invasive annual grasses: re-envisioning approaches in a changing climate. Journal of Soil and Water Conservation. 78(2):95-103. https://doi.org/10.2489/jswc.2023.00074.
Snyder, K.A., Richardson, W., Browning, D.M., Lieurance, W., Stringham, T.K. 2023. Plant phenology of high-elevation meadows: Assessing spectral responses of grazed meadows. Rangeland Ecology and Management. 87:69–82. https://doi.org/10.1016/j.rama.2022.12.001.
Edwards, B.L., Webb, N.P., Van Zee, J.W., Courtright, E.M., Cooper, B.F., Metz, L., Herrick, J.E., Okin, G., Duniway, M.C., Tatarko, J., Tedela, N., Newingham, B.A., Pierson Jr, F.B., Toledo, D.N., Van Pelt, R.S. 2021. Parameterizing an aeolian erosion model for rangelands. Aeolian Research. 54.Article 100769. https://doi.org/10.1016/j.aeolia.2021.100769.
