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ARS Home » Pacific West Area » Reno, Nevada » Great Basin Rangelands Research » Research » Research Project #424847

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

Location: Great Basin Rangelands Research

2014 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. • Sub-objective 1.3: Determine how cheatgrass invasion and climate change interact with one another to affect the structure and long-term persistence of sagebrush (Artemisia tridentata ssp.) populations. 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 1.3: Determine how cheatgrass invasion and climate change interact with one another to affect the structure and long-term persistence of sagebrush. Hypothesis: Climate change and competition from cheatgrass will independently and interactively reduce the persistence of sagebrush populations. Field studies will examine sagebrush demography across its geographic range. Growth chamber experiment will study interactions of atmospheric CO2 levels, soil moisture, and plant competition on sagebrush germination, seedling survival, and growth parameters. 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 second annual report for project 5370-13610-001-00D that began in June of 2013 and is affiliated with the Great Basin Rangelands Research Unit (GBRRU) in Reno, Nevada. GBRRU undertakes basic and applied research to improve the health and sustainability of Great Basin rangelands. Much of the Great Basin has experienced three years of below normal precipitation. Feed for livestock and wildlife is scarce, some federal grazing lands have been closed to permittees, and the specter of wildfire looms due to extremely dry and flammable vegetation. Field research under these conditions is perilous; rehabilitation seedings often fail and vegetation we wish to experiment with simply did not grow in some areas. Unfortunately, the drought has had minimal effects on the expansion of invasive plants threatening Great Basin ecosystems. For example, the exotic annual cheatgrass, although smaller in stature and less dense, still produces copious quantities of seeds and the dry plants are ready to fuel a wildfire. Objective 1: The Great Basin has undergone more environmental change in the last 250 years than it has since the close of the last ice age largely due to invasion by the annual grass, cheatgrass. The GBRRU has made considerable progress in both basic and applied research that may lead to greater efficacy of control. The unit has expanded the ‘genetic toolbox’ of cheatgrass, which will increase our understanding of its reproductive ecology. Forty-two primer pairs developed to amplify polymorphic single sequence repeat (SSR) markers in bread wheat were selected from throughout 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. These 4 markers were applied to samples from several of 14 cheatgrass populations collected from throughout the Great Basin, and again they consistently amplified. 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. The use of wheat SSRs will supplement our approach to expanding the genetic toolbox available for cheatgrass studies. The latter utilizes our IonTorrent Next Generation DNA Sequencing system and will generate hundreds to thousands of new SSR markers spread throughout the cheatgrass genome. Our applied research to combat cheatgrass not only includes genetic technology; but additionally centers on field research with new herbicides and formulations, new plant materials, new seeding methodologies, and timing of seeding. We have made progress in mitigating drought effects by testing new plant materials more adapted to very arid rangelands including the USDA-ARS release, ‘Vavilov’ Siberian wheatgrass. The GBRRU continues to cooperate with the USDA-ARS, Logan, Utah Unit in field-testing new plant materials that are more drought tolerant. We have made progress utilizing new herbicides and rates of application to create vegetation fallows, which increases stored subsoil water and enhances revegetation success even in dry years. Since the late 1800’s, western juniper has expanded about ten-fold with concomitant loss of sagebrush habitat. The GBRRU has made progress to decipher the underlying mechanisms of expansion. Samples of 100 western juniper berries have been collected semi-annually at two field sites in Northeast California and dissected in the laboratory to quantify insect infestations that affect seed viability in western juniper. To date, this has resulted in the identification of 38 arthropod species (mostly insects) associated with juniper berries, many of which are seed predators. These data will be used to parameterize juniper seed production in models of western juniper expansion through seed dispersal, and may inform future biological control efforts directed at western juniper. Trail cameras have identified numerous bird and small mammal species that feed on juniper berries and/or seeds. Several fruit-eating bird species (e.g., American robins, Townsend’s solitaires) and seed-caching small mammals (e.g, yellow pine chipmunks, California kangaroo rats) are also important dispersers of juniper seeds. Objective 2: The GBRRU has had a long history of researching wildfires, centering on revegetation technologies and how wildfires affect soil chemistry. This past year we undertook a project where we combined post-fire revegetation with soil analyses to quantify how post-fire soil microsites affect seeding success. We have sampled soils monthly from November of 2013 (wildfire occurred in October 2013) to the present (last sampling was in June, 2014). No previous research has undertaken such detailed temporal or spatial analysis of post-fire soil chemistry. Relative to unburned control sites, the most significant changes in soil chemistry occurred in burned sagebrush canopies, likely due to elevated heating. Surprisingly, burned sagebrush canopies have as much as 10 times greater manganese availability than their unburned counterpart and such increased availability may benefit cheatgrass. Also benefitting cheatgrass, post-fire shrub canopies have elevated levels of nitrogen availability, mostly due to ammonium. Even though post-fire soil has far higher nitrogen availability, the unburned soil has far greater potential for nitrogen to mineralize. Over time nitrogen will be more available, but on a slow release basis. A slower release of nitrogen would not be as beneficial to fast growing plants such as cheatgrass. Objective 3: The GBRRU has made progress utilizing native seed-eating desert rodents to essentially sow desirable plants. In previous research, millet was broadcasted as a “diversionary seed” in areas where heteromyid rodents typically cache Indian ricegrass seeds in abundance. 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. However, we believe that the results of these experiments would have yielded even better seedling establishment of Indian ricegrass if a diversionary seed that is more highly preferred than millet had been used. Millet has a very similar preference ranking to the target seed, Indian ricegrass, so a more highly preferred seed should result in fewer of the target seeds being recovered for consumption. Consequently, 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. Thus, a mixture of desirable commercial seeds may be more effective than a single type of diversionary seed in reducing the number of Indian ricegrass caches that rodents recover, leaving more to potentially establish seedlings. In November 2013, we attempted to field test a mixture of preferred diversionary seeds by broadcast seeding at two of the sites in western Nevada where our previous diversionary seeding research was conducted. Due to having a dry 2013 fall season and the prediction of continuing drought through the 2013-14 winter, we reduced the scope of this experiment (smaller plots, one site omitted) and deferred the more costly drill seeding experiments for a year with more favorable conditions (hopefully 2014-15). As a result of exceedingly dry conditions, we did not get any successful seedling recruitment of Indian ricegrass in spring 2014 from our 2013 broadcast seeding effort. The GBRRU has made progress on how to assess non-Federal western rangeland soil loss rates and identify areas of vulnerability for accelerated soil loss using Natural Resources Conservation Service (NRCS) National Resources Inventory (NRI) data and the Rangeland Hydrology and Erosion Model (RHEM). The RHEM tool was used to estimate runoff and soil loss at the hillslope scale for over 10,000 NRCS NRI sample points in 17 western states on non-Federal rangelands. The national average annual soil loss rate on non-Federal rangeland is estimated to be 1.4 ton ha-1 year-1. Nationally, 20% of non-Federal rangelands generate more than 50% of the average annual soil loss. Between 23% and 29% of the Nation’s non-Federal rangelands are vulnerable to accelerated soil loss (soil loss > 2.2 ton ha-1 event -1) if assessed as a function of vulnerability to a runoff event > 25 years. Results have been summarized and submitted for publication. GBRRU scientists have taken advantage of recent developments in low cost structure from motion (SFM) technologies to develop new techniques to acquire high resolution soil microtopography data at a fraction of the cost of conventional surveying or LIDAR techniques. The SFM technology is being used to quantify soil erosion processes on rangelands. These new photogrammetric methodologies often lack easily accessible error metrics and are hence difficult to evaluate. The GBRRU team developed the framework to evaluate the SFM approach for soil microtopography measurement through assessment of uncertainty sources and quantification of their potential impact on overall 3D reconstruction of the soil surface. Sensitivity analysis identified camera principal point (image projection centre) as the dominant source of calibration-induced uncertainty. Overall, surface elevation values estimated from this technology estimated surface microtopography to within 2 mm. This new technology provides an independent validation of soil erosion prediction models. Results have been summarized and submitted for publication.

1. Drought helps in revegetating sites dominated by cheatgrass. Recent drought conditions have impacted most of the Great Basin. The very favorable precipitation of 2010/2011 produced much carry-over fuel on Great Basin rangelands. These fuel loads, which contained the highly invasive and flammable cheatgrass, contributed to the devastating 2012 wildfire season whereas more than 1 million acres burned within the Great Basin. Drought conditions have occurred following the 2012 wildfire season and have contributed to extreme failures of post-fire rehabilitation/restoration activities. ARS scientists at the Great Basin Rangelands Research Unit (GBRRU) in Reno, Nevada, have evaluated soil-active herbicide/fallow treatments and with excellent cheatgrass control (97.8%) during this same time period, the GBRRU has recorded a more than 800% increase in emergence and initial establishment of seeded species in the treated plots versus the control plots. The control of cheatgrass and the fallow of these treated sites have 40-45% more available moisture than untreated sites, which is critical to germination, emergence and establishment of seeded species.

2. Fuel treatments can save money and reduce the threat of wildfires in the Great Basin. A research team from the ARS Great Basin Rangelands Research Unit (GBRRU) in Reno, Nevada, and University of Nevada, Reno, found that fuel treatments to reduce the probability of wildfire for Wyoming sagebrush and mountain big sagebrush communities is economically justified in terms of wildfire suppression cost savings only before cheatgrass has become established. Fuel treatments have expected net benefits in terms of wildfire suppression costs averted of $90 to $358 per acre depending on specific site conditions. In closed-canopy pinyon and juniper stands average wildfire suppression costs are higher with fuel treatment than without, when the trees have encroached into sagebrush plant communities. This counterintuitive result is due to the possibility of treatment failure and converting pinyon and juniper woodlands to cheatgrass dominated landscapes. Fuel treatments that successfully restore Wyoming and mountain big sagebrush sites have the added benefits of reducing soil erosion by up to 3 fold in addition to saving money from not fighting wildfires.

3. Perennial grasses suppress cheatgrass and aid in revegetating Great Basin rangelands. Invasion of the exotic annual cheatgrass into the intermountain West has been an ecological disaster. ARS researchers in Reno, Nevada, have demonstrated that healthy and dense stands of perennial grasses suppress cheatgrass. We have explored underlying mechanisms responsible for suppression. Our research indicates that established perennial grasses partially reduce the competitive ability of cheatgrass by lowering the availability of soil nitrogen, co-opting of biological soil space by perennial roots, and allelopathic influences. Greater understanding of the suppression processes will likely improve long-term success in rehabilitating cheatgrass-infested rangelands.

4. Knowing soil phosphorus levels can aid in determining how to successfully reduce the impact of perennial pepperweed in the Great Basin. Perennial pepperweed is a Eurasian crucifer invading wetland and riparian habitats throughout the intermountain west. For nearly 20 years, ARS scientists at the Great Basin Rangelands Research Unit, Reno, Nevada, have monitored the invasion of perennial pepperweed at the Honey Lake Wildlife Refuge in Northeastern California. From its peak in 1998-2000, stem density and stature of perennial pepperweed has naturally declined and has almost been completely replaced by tall wheatgrass planted nearly 30 years earlier as nesting habitat for migratory waterfowl. Our data suggest that declining phosphorus availability deeper in the soil profile, due to biogeochemical cycling by perennial pepperweed, has altered the competitive balance between pepperweed and the wheatgrass, now favoring the grass. The utility of the research is that managers can triage perennial pepperweed invasions: high soil phosphorus levels deep in the soil profile will likely require expensive herbicidal control strategies; low phosphorus levels will only require a relatively short period of time, when perennial pepperweed naturally loses its competitive ability.

5. Determining soil nutrient and chemical status is required to successfully revegetate salt desert plant communities. The manager of Maggie Creek Ranch near Wells, Nevada has sought help to understand recent seeding failures. ARS scientists at the Great Basin Rangelands Research Unit in Reno, Nevada, have analyzed his soils and have tested a variety of plant materials in the problematic soils. Soil salinity is a problem and may require sowing of more salt-tolerant grasses and forbs. Our recommendation to the manager is to sow Siberian Wheatgrass as it performed by far the best in the soils tested. Moreover, the soils tested are quite low in phosphorus availability and we would recommend supplementation with phosphorus. This research represents the utility of ARS research and laboratory facilities to directly serve our constituent stakeholders.

Review Publications
Clements, C.D., Young, J.A., Harmon, D.N., Blank, R.R. 2014. Rehabilitation of cheatgrass-infested rangelands: management. The Progressive Rancher. 14(1):28-29.
Johnson, D.W., Walker, R.F., Glass, D.W., Stein, C.M., Murphy, J.B., Blank, R.R., Miller, W.W. 2014. Effects of thinning, residue mastication, and prescribed fire on soil and nutrient budgets in a Sierra Nevada mixed conifer forest. Forest Science. 60:170-179.
Roaldson, L.M., Johnson, D.W., Miller, W.W., Murphy, J.D., Walker, R.F., Stein, C.M., Glass, D.W., Blank, R.R. 2014. Prescribed fire and timber harvesting effects on soil carbon and nitrogen in a pine forest. Soil Science Society of America Journal. DOI: 10.2136/sssaj2013.08.0350nafsc.
Weltz, M.A., Spaeth, K., Taylor, M.H., Rollins, K., Pierson, F., Jolley, L., Nearing, M., Goodrich, D., Hernandez, M., Nouwakpo, S.K., Rossi, C. 2014. Cheatgrass invasion and woody species encroachment in the Great Basin: Benefits of conservation. Journal of Soil and Water Conservation. 69(2):39A-44A.
Haubensak, K., D'Antonio, C., Embry, S., Blank, R.R. 2014. A comparison of Bromus tectorum growth and mycorrhizal colonization in salt desert versus sagebrush habitat. Rangeland Ecology and Management. Available:
Blank, R.R. 2013. Freeze-agglomeration: An alternative mechanism for clay film formation. Soil Horizons. 54:4.
Clements, C.D., Young, J.A., Harmon, D.N., Blank, R.R. 2013. Rehabilitation of cheatgrass-infested rangelands: concepts. The Progressive Rancher. 13(6):30-31.
Clements, C.D., Young, J.A., Harmon, D.N., Blank, R.R. 2013. Rehabilitation of cheatgrass-infested rangelands: applications and practices. The Progressive Rancher. 13(7):30-31.
Morris, L.R., Monaco, T.A., Blank, R.R., Sheley, R.L. 2013. Long-term redevelopment of resource islands in shrublands of the Great Basin, USA. Ecosphere. 4:12.
Morris, L.R., Monaco, T.A., Blank, R.R., Leger, E., Sheley, R.L. 2013. Land-use legacies of cultivation in sagebrush ecosystems affect soil nutrients and plant growth nearly a century after cultivation. Plant Ecology. 214:831-844.
Blank, R.R., Morgan, T.A., Clements, C.D., Mackey, B.E. 2013. Bromus tectorum L. invasion: Changes in soil properties and rates of bioturbation. Soil Science Society of America Journal. 178:281-290.
Blank, R.R., Morgan, T.A. 2013. Soil engineering facilitates Downy brome (Bromus tectorum L.) growth - A case study. Invasive Plant Science and Management. 6:391-400.
Perkins, L.B., Blank, R.R., Ferguson, S.D., Johnson, D.W, Lindemann, W.C, Rau, B.M. 2013. Quick start guide to soil methods for ecologists. Perspectives in Plant Ecology, Evolution and Systematics. 15:237-244.
Nouwakpo, S.K., Huang, C., Weltz, M.A., Pimenta, F., Chagas, I., Lima, L. 2013. Using fluidized bed and flume experiments to quantify cohesion development from aging and drainage. Earth Surface Processes and Landforms. DOI: 10.1002/esp.3477.