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Research Project: Invasive Species Assessment and Control to Enhance Sustainability of Great Basin Rangelands

Location: Great Basin Rangelands Research

2018 Annual Report

The Great Basin is the largest North American desert covering more than 50 million hectares. Major vegetation types in the Great Basin include: salt desert shadscale/greasewood, sagebrush/bunchgrass and mountain shrublands, pinyon/juniper woodlands, subalpine forests, and alpine tundra. The region has extremely variable climate both spatially and temporally and a complex mixture of public and private land ownership. Ranching, mining, and recreation form the basis of rural economies. Over 20% of Great Basin ecosystems have been significantly altered by invasive plants. This land conversion has resulted in dramatic reductions in forage availability, wildlife habitat, and biodiversity, has increased wildfire frequency and intensity, and altered the hydrologic cycle. Critical research needs addressed in this project are: (1) ecology and control of invasive weeds, (2) rehabilitation of degraded rangelands, (3) maintaining/enhancing healthy rangelands, and (4) quantifying the impact of management practices. Objective 1. Assess and quantify ecological conditions and biotic processes that maintain healthy rangelands, improve forage production, and enhance recovery of degraded sagebrush, and pinyon/juniper woodlands under uncertain climatic conditions in the Great Basin. • Sub-objective 1.1: Expand the ‘genetic toolbox’ to allow us to determine how the reproductive ecology of invasive annuals affects the structure and function of selected Great Basin ecosystems. • Sub-objective 1.2: Determine mechanisms underlying the expansion of native western juniper (Juniperus occidentalis) woodlands. Objective 2. Assess and quantify interactions between annual grasses and fire on watershed processes and ecosystem services under uncertain climatic conditions. Objective 3. Develop and transfer innovative management approaches and technology for conserving and rehabilitating sagebrush, pinyon/juniper woodlands, and salt desert shrublands to meet natural resource and agricultural production goals. • Sub-objective 3.1: Mechanistically understand how intact perennial grass communities resist invasion by annual grasses, especially cheatgrass. • Sub-objective 3.2: Provide management guidelines and transferable technologies to our stakeholders for establishing and enhancing native and introduced grasses, forbs, and shrubs in Great Basin ecosystems. Objective 4. Develop decision support tools for USDA to assess impact of type, location and number of management practices required to meet conservation and agricultural production goals nationwide. • Sub-objective 4.1: Enhance RHEM, KINEROS2, APEX, and SWAT models for assessing hydrology and erosion responses associated with management of disturbed vegetation states and transitions occurring on sagebrush-steppe ecological sites. • Sub-objective 4.2: As part of a national assessment, quantify soil loss on western rangelands.

Objective 1.1: Determine how the reproductive ecology of invasive annuals affects the structure and function of selected Great Basin ecosystems. Hypothesis: Occasional outcrossing facilitates expansion of cheatgrass across the intermountain west by selecting for new genotypes adapted to drier and more alkaline sites. IonTorrent® platform will be utilized to identify new single-nucleotide polymorphisms (SNPs) in cheatgrass to document if outcrossing is occuring. Objective 1.2: Determine mechanisms underlying the expansion of native western juniper woodlands. Hypothesis: Quantify rodent preferences to either juniper berries hand-collected or passed through the gut of a Robin and determine percent germination and seedling establishment between treatments. Objective 2: Assess and quantify interactions between annual grasses and fire on watershed processes and ecosystem services. Hypothesis: Conversion of Wyoming sagebrush community to cheatgrass, as a result of wildfire, will negatively alter runoff and erosion. Rainfall simulation will be used to quantify soil erosion in intact sagebrush and ecosystems converted to annual grass dominance and predict soil erosion with the Rangeland Hydrology and Erosion Model (RHEM). Objective 3.1: Mechanistically understand how intact perennial grass communities resist invasion by cheatgrass. Hypothesis: Healthy, robust, and intact perennial grass communities facilitate resistance to invasion by cheatgrass. Growth of cheatgrass will be contrasted in soil occupied by established perennial grasses and in unoccupied soil in greenhouse and field studies. Objective 3.2: Provide management guidelines and transferable technologies to our stakeholders for establishing and enhancing Great Basin ecosystems. Hypothesis: Combined application of appropriate soil-active herbicides and optimal plant materials will enhance revegetation/restoration success on cheatgrass-infested rangelands. Objective 4: Enhance ARS natural resource models (e.g. RHEM) for assessing hydrology and erosion responses associated with management of disturbed vegetation states and transitions occurring on sagebrush-steppe ecological sites. Hypothesis: Runoff and soil erosion will increase when either pinyon/juniper or annual grasses invade sagebrush-steppe ecosystems. An instrumented watershed, Porter Canyon in central Nevada, will be used to evaluate the impact of cheatgrass invasion and pinyon/juniper woodlands on surface runoff, soil loss and sediment yield. Data will be used to evaluate model performance and measure utility of model to assess conservation practices.

Progress Report
This is the final report for this project which terminated in June 2018, and has been replaced with a bridging project, 2060-13610-002-00D. Substantial results were realized for all four objectives and sub-objectives during the term of the project. Our research addressed goals in National Program 215, Component 1, Improved Rangeland Management for Enhanced Livestock Production, Conservation, and Ecological Services. Sub-objective 1.1: Considerable progress was made in developing and identifying new genetic markers for the study of cheatgrass population genetics. Forty-two primer pairs developed to amplify polymorphic single sequence repeat (SSR) markers in bread wheat were selected from the bread wheat genome for screening in cheatgrass. Twelve of these SSRs produced amplicons when screened in cheatgrass and four consistently amplified one or two DNA fragments. This indicates that many of the thousands of SSRs that have been developed for bread wheat are applicable to cheatgrass genetic studies. Since the functional significance of many bread wheat markers is already established, these SSRs may be useful for identifying functional genetic adaptations that favor invasiveness in cheatgrass. We conducted DNA sequencing runs on cheatgrass plants collected throughout the Great Basin. DNASTAR Lasergene SeqNinja software was acquired and we initiated bioinformatic analyses to contrast genetic variation among numerous cheatgrass populations collected throughout the Great Basin and Mohave desert. Cheatgrass genotypes clustered into distinct environmental conditions, with one genotype adapted to extremely xeric conditions and another one appears to be adapted to alkaline soils. Sub-objective 1.2: We studied specific animal vectors responsible for dispersing Western juniper seeds. Experiments were conducted in exclosures at two field sites in Northeast California to quantify rates at which animals harvested Western juniper berries and seeds that were removed from berries. Several fruit-eating bird species (e.g., American robins, Townsend’s solitaires, cedar waxwings) consume berries and defecate the seeds, and seed-caching small mammals (e.g, yellow pine chipmunks, California kangaroo rats, pinyon mice) are secondary dispersers of juniper seeds defecated by birds. Experiments with radiolabeled seeds showed that these rodent species bury the seeds in caches, often in microsites that favor seed germination and seedling establishment. Germination only occurred in seeds that were removed from juniper berries (as occurs with gut passage of berries through birds) and buried (as occurs when rodents cache defecated seeds). The germination rate of seeds was enhanced after passing through birds. Quantitative data from this work will be used to parameterize predictive models of western juniper expansion. This research is being extended to a second juniper species, Utah juniper, in the next project cycle as it is expanding across the Great Basin. Objective 2: Over twenty percent of Great Basin ecosystem functions and processes have been altered by invasive annual grasses and expanding native conifers. Changes in plant functional type and cover together with climatic variability have resulted in dramatic reductions in forage availability, wildlife habitat and increased wildfires. To address this issue, an ARS team of scientists in Reno, Nevada, in association with ARS scientists in Tucson, Arizona, and Boise, Idaho, initiated research to document the influence of invasive species on hydrologic processes. Research determined that hydrologic processes have been altered (i.e., acceleration in soil erosion) and degradation of ecosystem goods and services have occurred. The team initiated a series of experiments to remove encroaching conifers and demonstrated that sagebrush and native grasses can be restored with improvement in hydrologic processes. Data from these experiments was used to develop the Rangeland Hydrology and Erosion Model (RHEM). RHEM assesses the current status and risks of soil erosion at hillslope scale. In addition, RHEM evaluates the benefits of alternative conservation practices to determine the most cost-effective approach. This tool has been transferred to the Natural Resources Conservation Service (NRCS), Bureau of Land Management, Bureau of Reclamation, Jordan, China, and Kazakhstan. The RHEM tool is now being used by NRCS and the Governments of Kazakhstan and Jordan to develop Ecological Site Descriptions and identify where conservation would be most constructive. Future research will focus on modifying RHEM to address saline soils and developing land treatments that are cost effective in reducing impacts of invasive species on rangeland health. Sub-objective 3.1: Substantial progress was made in mechanistically understanding how intact perennial grass communities resist invasion by annual grasses, specifically cheatgrass. A series of field and greenhouse experiments have revealed that perennial grass suppression of cheatgrass is multi-faceted, affected by perennial grass age and vigor, and declines steadily with increasing distance from the suppressive plant. Cheatgrass biomass can be reduced by over 95 percent if within 10 centimeters of a perennial grass. One mode of suppression is through decreased soil nitrogen availability; cheatgrass requires high levels of soil nitrogen to attain maximal growth. Established perennial grasses also increase the ratio of ammonium-nitrogen to nitrate-nitrogen in the soil, which suggests inhibition of nitrification. Maintaining high ratios of ammonium-nitrogen to nitrate-nitrogen is detrimental to the growth of cheatgrass as it prefers to uptake nitrogen in the nitrate-form. Several experiments have shown that a portion of cheatgrass suppression is due to occupation of soil space by perennial grass roots, thereby, co-opting movement of cheatgrass roots into the occupied space. This type of suppression is considered allelopathy; however, experiments were inconclusive regarding whether perennial grass roots exudate chemicals that suppress cheatgrass. Sub-objective 3.2: New technologies were developed to rehabilitate degraded Great Basin rangelands. Through experimentation, progress was made in decreasing cheatgrass densities through mechanical and chemical weed control practices. Mechanical treatments, disking prior to cheatgrass seed maturity, reduced cheatgrass densities by more than 80 percent while increasing desirable seeded species emergence and establishment by 244 percent. Chemical treatments, pre-emergent soil-active herbicides, decreased cheatgrass densities by as much as 97.8 percent and increased desirable seeded species emergence and establishment by more than 600 percent. These weed control practices increase available soil nitrogen, which is critical for perennial seedling development by sixteen-fold and increased available soil moisture by more than 40 percent. Increased perennial grass establishment decreased cheatgrass and associated fuels by more than 93 percent, decreasing the chance, rate, spread and season of wildfires and improving forage resources and wildlife habitats. Based on successful field validation, this technology has been transferred and is currently being implemented by Newmont Mining Corporation, which treated 6,000 acres in 2017 and is in the process of treating another 9,000 acres in 2018. Diversionary seeding was used to aid the recruitment of Indian ricegrass, an important native bunchgrass providing forage on winter ranges in the Great Basin. Recruitment of Indian ricegrass is facilitated by desert rodents, which cache its seeds. The feasibility of utilizing the seed dispersal services of native animals as a passive restoration strategy was successfully tested at a field scale for the first time by broadcasting millet as a “diversionary seed” over one-hectare plots in areas where heteromyid rodents typically cache Indian ricegrass seeds. Under these circumstances, rodents cached and preferentially recovered the preferred diversionary seeds before beginning to consume the less desirable target seeds. Consequently, more target seeds were available for emergence as seedlings using this passive restoration scheme, and we measured greater productivity of Indian ricegrass seedlings on plots treated with diversionary seeds. To test for a superior diversionary seed than millet, we conducted laboratory seed choice experiments on captive rodents using 6 commercially available seed types (millet, oil sunflower, canary grass, cracked corn, white wheat, and black thistle) and found that many animals did indeed prefer certain seeds over Indian ricegrass, but this varied among individual rodents. We intend to continue this line of research in the next project cycle. Objective 4: ARS scientists in Reno, Nevada, worked with ARS scientists in Tucson, Arizona, and Boise, Idaho, and collaborators, to develop a framework for inclusion of key ecohydrologic feedbacks. Including the Rangeland Hydrology and Erosion Model (RHEM) into Ecological Site Descriptions (ESDs) enhances the utility of ESDs for assessing rangeland sustainability. The use of these concepts is critical in guiding development of conservation practices to enhance resilient-based management strategies. The scientific team has made progress on assessing sediment transport processes on western rangelands with RHEM. The RHEM tool is now used by NRCS as a standard method for use in national reporting of benefits of its conservation programs. Future research will refine statistical methods to enhance expansion factors using an integration of field sampling with remote sensing, which will enhance interpretation of the data at both local and national scales and make prioritization of conservation more effective.

1. Improving restoration practices to reduce wildfire threats. The accidental introduction and subsequent invasion of the annual grass, cheatgrass, to Great Basin rangelands, has decreased the fire return interval and increased the frequency with millions of dollars spent annually fighting wildfires. ARS scientists in Reno, Nevada, have been testing pre-emergent herbicides to control cheatgrass and open a window of opportunity to improve restoration success and diminish cheatgrass densities and associated fuels. This research has resulted in more than a 900 percent increase of perennial grasses, shrubs and forbs that successfully suppress cheatgrass. A decrease in associated fuels, significantly reduces the chance, rate, spread and season of wildfires associated with cheatgrass dominance. Converting cheatgrass-dominated habitats back to perennial grasses, forbs and shrubs, has substantially improved sustainable grazing resources as well as improved diversity, edge effect and stand vigor. This success leads to overall health of the habitat and decreases the threat of wildfire which is so devastating to sensitive species such as sage grouse and mule deer.

2. Medusahead reciprocal garden study. In the western U.S., rangelands invaded by the exotic annual grass medusahead have had livestock carrying capacity reduced by 75 percent. In cooperation with researchers at the University of California Riverside, ARS scientists at Reno, Nevada, completed a four-year reciprocal transplant study to decipher factors important in the invasion ecology of medusahead. Medusahead seeds from three Eurasian (native) sites (Turkey, Greece, and Bulgaria) and three northeastern California (invaded) sites were sown in all six soils. Soils from invaded areas in northeastern California had significantly greater bicarbonate-extractable phosphorus, cation exchange capacity, extractable calcium and manganese availability than native soils from Eurasia. Plants grown from seeds originating from invasive populations had significantly more above-ground biomass than native plants, but only when grown in northeastern California soils. Seed source (invasive vs. native) significantly affected nutrient uptake. Greater fertility of northeastern California soils explains medusahead’s invasiveness. With Natural Resources Conservation Service soil maps risks assessment maps can be developed and conservation practices implemented to reduce the invasion in areas where medusahead has not been established.

3. Salt loading of the Colorado River. The Colorado River and its tributaries provide municipal and industrial water to more than 40 million people and irrigation water to more than 4 million acres of land in the U.S. and Mexico. Dissolved solids input into the Colorado River are estimated to cost about $383 million per year and estimated annual costs of damage by water erosion and excessive sediment in surface waters in the U.S. are $16 billion for water users and $44 billion for on- and off-site impacts. ARS scientists in Reno, Nevada, and their collaborators, evaluated the role of canopy cover in reducing salt loading in Mancos shale-dominated landscapes in central Utah using rainfall simulation techniques. They found that naturally occurring vegetation cover (3 to 33 percent) was not sufficient to reduce high runoff and salt transport capacities on these ecological sites. It was determined that due to low vegetation cover and an extensive network of preexisting concentrated flow and rill networks, salt transport was only slightly reduced as vegetation cover increased. New methods to quantify tortuosity of concentrated flow paths need to be incorporated in rangeland erosion and salt transport models to accurately reflect benefits from revegetation efforts designed to increase plant cover and reduce salt loading to the Colorado River.

4. Increasing native perennial grasses to suppress cheatgrass. The introduced and invasive annual grass, cheatgrass, has increased the chance, rate, spread, and season of wildfires resulting in significant loss of native perennial grasses, shrubs and forbs. ARS Scientists in Reno, Nevada, are testing new pre-emergent herbicides to control cheatgrass, and seeding native perennial grasses to increase diversity and improve ecosystem function in arid Great Basin rangelands. Using this integrated weed control program, we have successfully seeded native perennial grasses and improved ecosystem function. Using this new technology, native perennial grass densities increased from an average of 47 per acre to more than 120,000 per acre, which improves the sustainability of grazing resources and wildlife habitat as well as decreasing cheatgrass densities, and associated fuels, by more than 93 percent.

5. Increasing big sagebrush densities for sagebrush obligate species. Recurring wildfires have significantly decreased big sagebrush stand densities resulting in loss of critical shrub habitat for sagebrush obligate species such as sage grouse and mule deer. ARS scientists in Reno, Nevada, tested big sagebrush transplanting methodologies to increase big sagebrush in crested wheatgrass stands to improve shrub density and stand vigor. Their efforts resulted in a six-fold increase in big sagebrush density. Using proper methodologies, fall transplanting versus spring transplanting of big sagebrush in crested wheatgrass stands has increased the density of big sagebrush, thereby improving habitat for the threatened sage grouse. The increase in shrub density improves wildlife habitat and ecosystem function while reducing livestock-wildlife conflicts.

6. Suppression of cheatgrass by crested wheatgrass. Long-term suppression of the invasive annual cheatgrass is predicated on establishment of healthy stands of perennial grasses. ARS scientists in Reno, Nevada, completed a two-year greenhouse study to increase mechanistic understanding of suppression. They established the perennial grass, crested wheatgrass, in large tubs and cheatgrass was sown at distances of ten, thirty-eight, and seventy centimeters (cm) from the crested wheatgrass. Overall, relative to cheatgrass grown at a distance of seventy cm, plants sown at ten cm were suppressed ninety-six percent and plants sown at thirty-eight cm were suppressed fifty-six percent. Significant factors that explained cheatgrass suppression included tissue manganese-to-copper mole ratios, tissue magnesium and nitrogen concentration, and soil resin-available phosphorus. The data suggest suppression of cheatgrass is due to reduction of nutrient availability by established crested wheatgrass; however, field suppression may also be aided by reduced water availability due to uptake by established crested wheatgrass.

7. Seed caching and diversionary seeding to improve establishment of native bunchgrass. Seedling production of Indian ricegrass, a native bunchgrass that supplies an important source of livestock forage on arid grazing lands, is enhanced by the seed caching activities of desert rodents. ARS scientists in Reno, Nevada, applied this finding by introducing the concept of diversionary seeding in which inexpensive commercial seeds are broadcast on rangelands to reduce the chance that seed-eating rodents recover and consume their natural caches of Indian ricegrass seeds. Plots on which diversionary seeds were applied had greater production of Indian ricegrass seedlings from rodent caches than did plots without diversionary seeds. They followed this work with an experimental study demonstrating that seed caching, which is central to the diversionary seeding concept, also enhances long-term survival of the plants. Most recently, they demonstrated in a paper being published in Western North American Naturalist that the husk of Indian ricegrass seeds masks internal odors that permit rodents to locate buried seeds. Thus, after seeds have been cached, they are less vulnerable to consumption by rodents other than the individual that made the caches – another piece of evidence regarding apparent coevolution between desert rodents that disperse seed and Indian ricegrass.

8. Effect of soil active herbicides on soil nutrient availability. Very sparse literature exists on the effect of pre-emergent herbicides on nutrient availability. As part of a larger rangeland rehabilitation project, on four sites in northern Nevada, ARS scientists in Reno, Nevada, quantified the effect of the herbicides, Landmark®, Perspective®, and Plateau®, relative to controls, on surface soil nutrient availability. Samples were collected multiple times over two years. Overall, relative to the controls, mineral nitrogen, soil-solution sulfate, and bicarbonate-extractable phosphorus quantities were often elevated on herbicide-treated plots. In addition, on some sites, herbicide treatments affected micronutrient availability. We believe these changes in nutrient availability are largely a function of vegetation loss (lack of nutrient uptake and root exudation) due to the herbicides.

9. Effect of tree removal on Great Basin ecosystems. Land managers across the western U.S. are faced with selecting and applying tree-removal treatments on pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland-encroached sagebrush (Artemisia spp.) rangelands. However, current understanding of long-term vegetation and hydrological responses of sagebrush sites to tree removal is inadequate for guiding management. ARS scientists in Reno, Nevada, Boise, Idaho, and Tucson, Arizona, quantified the hydrologic impacts of mechanical tree removal, nine years prior, on vegetation, runoff, and soil erosion at two mid- to late-succession woodland-encroached sagebrush sites in the Great Basin. Tree removal increased hillslope scale density of sagebrush and perennial grass cover with minimal increase in cheatgrass cover or adverse impacts on surface runoff and soil erosion. This research has been incorporated into the Rangeland Hydrology and Erosion Model and is being transferred to the Natural Resource Conservation Service, Bureau of Land management, and Bureau of Reclamation for improving water quality.

Review Publications
Clements, D.D., Harmon, D.N., Blank, R.R., Weltz, M.A. 2017. Improving seeding success on cheatgrass-infested rangelands in Northern Nevada. Rangelands. 39(6):174-181.
Clements, D.D., Harmon, D.N. 2017. Four-wing saltbush (Atriplex canescens) seed and seedling consumption by granivorous rodents. Rangelands. 39(6):182-186.
Webb, N., Van Zee, J.W., Karl, J.W., Herrick, J.E., Courtright, E.M., Billings, B., Boyd, R., Chappell, A., Duniway, M., Derner, J.D., Hand, J., Kachergis, E., McCord, S., Newingham, B.A., Pierson Jr, F.B., Steiner, J.L., Tatarko, J., Tedela, N., Toledo, D.N., Van Pelt, R.S. 2017. Enhancing wind erosion monitoring and assessment for US rangelands. Rangelands. 39:85-96.
Carter, Z., Sullivan, B., Qualls, R., Blank, R.R., Schmidt, C. 2018. The effects of charcoal and pile burns on C and N Dynamics in Eastern Sierra Nevadan forested soils. Forests. 9(2):93.
Dimitri, L.A., Longland, W.S. 2018. The utility of animal behavior studies in natural resource management. Rangelands. 40:9-16.
Finzel, J., Seyfried, M.S., Weltz, M.A., Launchbaugh, K. 2015. Simulation of long-term soil water dynamics at Reynolds Creek, Idaho: Implications for rangeland productivity. Ecohydrology. 9:673-687.
Hernandez, M., Nearing, M.A., Stone, J.J., Pierson Jr, F.B., Wei, H., Spaeth, K., Heilman, P., Weltz, M.A., Goodrich, D.C. 2013. Application of a rangeland soil erosion model using NRI data in southeastern Arizona. Journal of Soil and Water Conservation Society. 68(6):512-525.
Nouwakpo, S., Weltz, M.A., McGwire, K., Williams, C.J., Al-Hamdan, O., Green, C.H.M. 2017. Insight into sediment transport processes on saline rangeland hillslopes using three-dimensional soil microtopography changes. Earth Surface Processes and Landforms. 42(4):681-696.