Location: Great Basin Rangelands Research
2024 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 progress for project 2060-22000-025-000D, titled, “Development of Ecological Strategies for Invasive Plant Management and Rehabilitation of Western Rangelands” which started in October 2020.
In support of Sub-objective 2A1, ARS researchers in Reno, Nevada, made good progress on the testing of three separate pre-emergent herbicides and their efficacy in controlling the exotic and invasive annual grass, cheatgrass. Pre-emergent herbicides effectively controlled and reduced cheatgrass on treated habitats. Soil samples continued to be collected revealing an increase in available soil moisture, available soil nitrogen as well as a significant reduction in cheatgrass seed bank densities. Following pre-emergent herbicide applications, the seeding of perennial grasses was conducted. The reduction in cheatgrass competition significantly increased limited soil nutrients and significantly increased seedling survival of seeded perennial grasses. This increase in perennial grass densities has resulted in continued control of cheatgrass through resource competition and has reduced cheatgrass associated fuel loads as well as improve nutritional perennial grass forage. This integrated approach reduces wildfire threats while improving grazing and wildlife resources. Preliminary data was presented at national and regional meetings as well as field tours.
For Sub-objective 2A, Experiment 2A2, ARS researchers in Reno, Nevada, 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. ARS researchers established an experiment on the Strawberry fire 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, they 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, they researchers continued to monitor soil moisture and temperature using probes, and measured soil stability and soil surface roughness. ARS researchers have concluded the data collection, written the methods portion of the manuscript, and are finalizing results. The results were presented at a national conference.
Under Sub-objective 2B and subordinate project #2060-21500-001-016-I, title "Soil, Water, Meadow and Rangeland Monitoring on the Desatoya Mountains Project", ARS researchers investigated and quantified critical rangeland water resources and assessed water use of pinyon and juniper, as well as the hydrologic responses of a meadow to tree treatments. 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, that 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. This research was done at the Porter Canyon Experimental Watershed in Nevada, where multiple experiments and long-term instrumentation are used to examine the ecosystem effects of tree control treatments. An additional year of data was added on to the responses of meadow groundwater levels and meadow soil moisture to the removal of pinyon and juniper. A manuscript was prepared using six years of data on the water transpired by 36 pinyon and 16 juniper trees. In addition, these data were scaled to the stand-level using tree basal area density of the sampled plots. Preliminary data was presented at two national meetings.
Accomplishments
1. Efficacy of pre-emergent herbicide reduces cheatgrass associated wildfire threats. The introduction of cheatgrass has significantly increased wildfire threats throughout the west. Great Basin rangelands have experienced nearly a 10-fold increase in cheatgrass occurrence at an alarming rate. Cheatgrass invasion has resulted in larger and more frequent wildfires that cause catastrophic damage to critical grazing and wildlife resources as well as threatening life and property. ARS researchers in Reno, Nevada, tested the efficacy of the pre-emergent herbicide indaziflam (Rejuvra®) to reduce the advancement of cheatgrass in habitats dominated by perennial vegetation. The efficacy of indaziflam on treated habitats has reduced cheatgrass densities by greater than 98% while extending the green period of perennial vegetation by as much as 20%. The ability of indaziflam to actively control cheatgrass by as much as four years significantly reduces cheatgrass and associated wildfire threats which protects critical habitats from catastrophic wildfires, while also providing an extended period of nutritional forage for livestock and wildlife.
Review Publications
Richardson, W., Stringham, T.K., Nuss, A.B., Morra, B., Snyder, K.A. 2023. Shifts in sage-grouse arthropod food sources across grazing and environmental gradients in upland meadow communities. Journal of Environmental Management. 348. Article 119261. https://doi.org/10.1016/j.jenvman.2023.119261.
Williams, C., Ellsworth, L.M., Strand, E.K., Reeves, M., Shaff, S.E., Short, K.C., Chambers, J.C., Newingham, B.A., Tortorelli, C. 2023. Fuel treatments in shrublands experiencing pinyon and juniper expansion result in trade-offs between desired vegetation and increased fire behavior. Fire Ecology. 19. Article 46. https://doi.org/10.1186/s42408-023-00201-7.
Young, S.L., Anderson, J.V., Baerson, S.R., Bajsa Hirschel, J.N., Blumenthal, D.M., Boyd, C.S., Boyette, C.D., Brennan, E.B., Cantrell, C.L., Chao, W.S., Chee Sanford, J.C., Clements, D.D., Dray Jr, F.A., Duke, S.O., Porter, K.M., Fletcher, R.S., Fulcher, M.R., Gaskin, J., Grewell, B.J., Hamerlynck, E.P., Hoagland, R.E., Horvath, D.P., Law, E.P., Madsen, J., Martin, D.E., Mattox, C.M., Mirsky, S.B., Molin, W.T., Moran, P.J., Mueller, R.C., Nandula, V.K., Newingham, B.A., Pan, Z., Porensky, L.M., Pratt, P.D., Price, A.J., Rector, B.G., Reddy, K.N., Sheley, R.L., Smith, L., Smith, M., Snyder, K.A., Tancos, M.A., West, N.M., Wheeler, G.S., Williams, M., Wolf, J.E., Wonkka, C.L., Wright, A.A., Xi, J., Ziska, L.H. 2023. Agricultural Research Service weed science research: past, present, and future. Weed Science. 71(4):312-327. https://doi.org/10.1017/wsc.2023.31.
Treminio, R.S., Webb, N.P., Edwards, B.L., Faist, A., Newingham, B.A., Kachergis, E. 2024. Spatial patterns and controls on wind erosion in the Great Basin. Journal of Geophysical Research-Biogeosciences. 129(1). Article e2023JG007792. https://doi.org/10.1029/2023JG007792.
