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

Location: Great Basin Rangelands Research

2016 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 fourth annual report for this project which began in June of 2013 and is affiliated with the Great Basin Rangelands Research Unit (GBRRU) in Reno, Nevada. The ARS scientists in Reno, Nevada, undertake basic and applied research to improve the health and sustainability of Great Basin rangelands. After four years of extreme drought, the winter of 2015-2016 brought above normal precipitation over much of the Great Basin. The extended drought did impact GBRRU field experiments and some milestones could not be met due to poor seed germination and minimal plant growth. The above-normal precipitation pattern, while welcome, has encouraged growth of weedy species such as cheatgrass resurrecting the specter of wildfires. The GBBRU has been and is greatly involved with post-wildfire rehabilitation technologies from herbicide testing, cultural techniques, and testing of plant materials. A major consequence of cheatgrass-fueled wildfires is the loss of sagebrush habitat for the endangered greater sage-grouse. The GBRRU undertakes research to rehabilitate cheatgrass-degraded rangelands, including re-introduction of sagebrush, to enhance habitat for sage-grouse and other wildlife. Progress was made on all four objectives and their sub-objectives, all of which fall under National Program 215, Component I, Improved Rangeland Management for Enhanced Livestock Production, Conservation, and Ecological Services. Our research falls under: Objective B.1. Develop strategies and practices for conserving healthy rangelands and restoring degraded lands under changing environmental conditions to meet a variety of ecosystem services objectives. Objective B.2. Develop decision support tools usable at multiple scales including landscape levels for inventorying and assessing rangelands; and, for selecting, implementing, and monitoring conservation and restoration practices. Objective C.1. Improve understanding of the fundamental relationships among management practices, ecological processes, and climatic variability to improve rangeland production, conservation and restoration. Sub-objective 1.1: ARS scientists in Reno, Nevada, conducted DNA sequencing runs on plants collected from numerous cheatgrass populations sampled throughout the Great Basin. This marks the initiation of expanding the genetic toolbox for cheatgrass studies, which utilizes our IonTorrent Next Generation DNA Sequencing system and will generate hundreds to thousands of new single sequence repeat (SSR)markers spread throughout the cheatgrass genome. Sequencing runs were being analyzed with GENEIOUS software, however we found this to be too cumbersome and are currently switching to using DNASTAR Lasergene and Primer 3 software. Completion of these analyses, which have been underway for several months, will allow us to identify hundreds of single nucleotide polymorphisms (SNPs) and SSRs. DNA extraction and PCR amplification are being conducted for additional populations collected in 2016 to expand the geographic coverage of our genetics studies. Sub-objective 1.2: Twenty-four seed caching trials were conducted with western juniper seeds at three field sites in North Eastern California. We also quantified removal rates of western juniper berries and seeds by animals. Video trail cameras were employed in both the caching experiments and seed/berry removal experiments to identify various bird and small mammal species feeding on berries and/or seeds. Several fruit-eating bird species (e.g., American robins, Townsend’s solitaires) consume berries and defecate the seeds, and seed-caching small mammals (e.g, yellow pine chipmunks, California kangaroo rats) are secondary dispersers of juniper seeds defecated by birds. This work was expanded over the past year to include Utah juniper at western Nevada field sites, resulting in completion of a M.S. degree by a student employed by the unit. Utah juniper berries are not consumed by birds, but are taken directly by seed-caching small mammals, bypassing a step in the dispersal system for western juniper. Objective 2: Rainfall simulation work has documented that, although cheatgrass is a non-native invasive annual grass that can dominate a site after fire, it does not necessarily have deleterious impacts on surface runoff and soil erosion processes. Runoff is a function of plant density, canopy cover, and total ground cover. If cheatgrass canopy cover and ground cover exceed sixty percent, then little soil erosion will occur on cheatgrass-dominated rangelands. These findings confirm the non-linear equation used in the Rangeland Hydrology and Erosion model developed by ARS scientists in Reno, Nevada, Tucson, Arizona, and Boise, Idaho. Additional research is being conducted by this team to understand how different vegetative treatments can reduce cheatgrass densities and impacts on ecosystem processes, while not altering normal hydrologic processes. Sub-objective 3.1: ARS scientists in Reno, Nevada, continue to make progress in understanding the underlying mechanisms by which established perennial grasses suppress invasive annual grasses. This past year, two greenhouse experiments were completed which evaluated the ability of established crested wheatgrass (a long-lived non-native perennial grass) and established “snowstorm” forage kochia (a non-native semi-shrub) to suppress the exotic annual grass cheatgrass. In the first experiment, to our surprise, newly established forage kochia suppressed cheatgrass more than newly established crested wheatgrass. In the second experiment, both crested wheatgrass and forage kochia were allowed to establish for nearly a year. In this experiment, there was no significant difference in the suppressive ability of crested wheatgrass or forage kochia. Sub-objective 3.2: In the Great Basin, almost no research has been done testing the effect of herbicide application on surface soil nutrient availability. This past year, field studies have been initiated to research the effect of the herbicides Plateau®, Landmark®, and Perspective® on soil nutrient availability. Data are preliminary, but herbicide-treated plots have greater water availability, greater nitrogen availability, and less nitrogen mineralization potentials than control plots. These plots will continue to be evaluated for two more years. We continue to make progress on how desert rodents impact specific plant species and species composition of arid plant communities. We conducted diversionary seeding experiments in 2014 and intended to resample for seedling emergence in 2016, but due to having dry fall and winter seasons in 2014, we did not get any successful seedling recruitment of Indian ricegrass from seeding efforts. However, related to this research, we did publish results of laboratory seed choice experiments on captive rodents using six commercially available seed types (millet, oil sunflower, canary grass, cracked corn, white wheat, and black thistle) and showed that many animals preferred certain seeds over Indian ricegrass, but this varied among individual rodents. Thus, we recommended a seed mixture when applying diversionary seeds rather than a single diversionary seed type. Sub-objective 4.1: In conjunction with ARS scientists in Tucson, Arizona, and Boise, Idaho, ARS scientists in Reno, Nevada, have developed and transferred the Rangeland Hydrology and Erosion Model (RHEM) to the Bureau of Land Management (BLM) and Natural Resources Conservation Service (NRCS). NRCS is actively working with ARS to have the model available for cost-effective conservation planning activity by 2017 on NRCS desktops. GBRRU scientists working with collaborators have developed a framework for inclusion of key ecohydrologic feedbacks using the RHEM for inclusion into Ecological Site Descriptions (ESDs) and thereby are enhancing the utility of ESDs for assessing rangeland sustainability. The use of these concepts will help in guiding development of conservation practices to enhance resilience-based management strategies. GBRRU scientists working with collaborators have developed a framework of assessing risk of soil erosion that has been incorporated into the RHEM assessment tool. This novel analysis allows for determining if a site is sustainable, at risk, or on a trajectory that is unsustainable and conservation is warranted. This new analysis technique should replace the concept of soil loss tolerance “T” on rangelands. Sub-objective 4.2: ARS scientists in Reno, Nevada, have made progress on this sub-objective by assessing sediment and salt transport processes on western rangelands and identifying areas of vulnerability for accelerated soil loss and salt loading to perennial rivers. RHEM is being modified to estimate salt loading from saline range uplands. Results of these rainfall simulations are being used to parameterize RHEM for saline and sodic soils on rangelands and to assess the feasibility of mitigation strategies for reducing salinity loads to western rivers. GBRRU scientists used data from rainfall simulation experiments in saline rangeland communities of the Upper Colorado River Basin to improve understanding on various sediment and solute transport processes in field conditions. Key findings from analyses include: (1) the dependence of deposition on plot slope and its independence on hydrologic and soil loss variables, (2) increased rill formation as a function of vegetation density and spatial location, (3) significance of accounting deposition processes in overall runoff energy quantification, (4) evidence of an equilibrium channel geometry with a given discharge that is marginally impacted by runoff duration, and (5) total dissolved solids in runoff is directly related to sediment yield. This work suggests that effective runoff, soil erosion, and salt load reduction strategies can be met by increasing vegetation.

1. Sagebrush rehabilitation increases habitat potential for the threatened sage grouse. Innovative approaches to enhance degraded big sagebrush (Artemisia tridentata)/bunchgrass communities are being tested by ARS scientists in Reno, Nevada. In the fall of 2013, we mechanically treated old decadent big sagebrush habitats in north-central Nevada using a Lawson Aerator, followed with seeding of perennial grasses and forbs to enhance wildlife and grazing resources. In the spring of 2016, the completed land treatment was occupied by sage grouse (Centrocercus urophasianus), where two new strutting/lek (breeding) habitats were established through this range improvement practice. This innovative treatment has provided excellent wildlife and grazing values to the area.

2. Transplanting sagebrush enhances wildlife habitat in the Great Basin. The conversion of formerly big sagebrush (Artemisia tridentata ssp. wyomingensis) bunchgrass communities to annual grass dominance, primarily cheatgrass (Bromus tectorum), greatly reduces habitat for wildlife, particularly the threatened greater sage-grouse. ARS scientists in Reno, Nevada, have researched new technologies to transplant big sagebrush. We compared fall versus spring transplanting into crested wheatgrass stands. Fall transplants had greater sagebrush survivability (46-62%) than spring transplants (13-34%). We believe greater fall precipitation contributed significantly to the success of fall transplants. Our technologies have utility in increasing sagebrush on rangelands, critical in providing habitat for the threatened greater sage-grouse.

3. Higher nutrient availability in U.S. soils explains the invasiveness of the exotic annual grass medusahead. Understanding the mechanisms that underlie the success of invasive plant species is integral to predicting and ameliorating their negative impacts. ARS scientists in Reno, Nevada, collaborating with scientists at the European Biological Control Lab in Montpellier, France, and the University of California in Riverside, California, completed a three-year study on the exotic invasive annual grass medusahead. The study used reciprocal garden methodology where seeds from its native range (Bulgaria, Greece, and Turkey) and seeds from its invasive range (three sites in north-eastern California) were grown in native soils and invasive soils. Overall, growth of medusahead was greatest in north-eastern California soils that have been invaded. Our data suggest that greater medusahead growth in invaded soils is driven by greater resource availability and fits into a developing paradigm that, because many Eurasian plants evolved under intense grazing and accelerated soil erosion, they are very competitive when they are introduced into western U.S. rangelands.

4. Establishment of desirable forage species is successful following cheatgrass weed control. Cheatgrass (Bromus tectorum) invasion has astronomically altered native plant communities throughout the Intermountain West and rehabilitation of cheatgrass-infested rangelands is a daunting task. The establishment of long-lived perennial grasses is key to suppressing cheatgrass and allowing plant succession to occur. ARS scientists in Reno, Nevada, implemented study plots in northern Nevada to test various herbicides to control cheatgrass and establish desirable plant species for wildlife and grazing resources. The application of herbicides reduced cheatgrass densities from an average of 210.6/m² down to 7.2/m², and at the same time, perennial grass densities, through release of residual plants and drill seeding desirable species, increased from 0.6/m² to 10.7/m². Cheatgrass control using appropriate herbicides is critical in successful rehabilitation of rangelands; if done properly, rangeland managers in the Great Basin will have greater rehabilitation success and potentially save millions of dollars in unsuccessful rehabilitation efforts.

5. Understanding seed dispersal of two juniper species is a critical for making informed management decisions. ARS scientists in Reno, Nevada, collaborated with a student studying for a masters degree at the University of Nevada, Reno, to study animal dispersal of seeds of two juniper species that are expanding on western rangelands. Despite being closely related, the dispersal systems of western and Utah juniper differ considerably. Western juniper berries are eaten by fruit-eating birds, and the seeds inside are defecated. Seed-eating rodents then harvest the seeds defecated by birds and cache them, where some seeds remain to germinate and establish new seedlings. Dispersal of Utah juniper seeds omits the first step in this strategy, as the berries are unattractive to fruit-eating birds, and instead are harvested directly by rodents, which remove the hardened berry pulp and cache the seeds. Although the dispersal systems differ, they both ultimately end with seed-eating rodents caching them, and this has important implications for managing juniper in areas where it is encroaching on shrub-lands or grasslands across the Great Basin.

6. Environmental impact statements should incorporate indicators of social and cultural impacts. An environmental impact statement (EIS) is required when a management action on public land may affect social and/or ecological systems. Currently, the EIS process focuses primarily on ecological impacts and does not integrate socio-economic components. Using a restoration project implemented by the Bureau of Land Management, ARS researchers in Reno, Nevada, developed a participatory social-ecological impact assessment (SEIA) to integrate social and economic components into the EIS process. We engaged stakeholders via questionnaires and workshops to identify social, ecological, and economic values in this particular restoration project. Our process has developed a peer-reviewed 2016 published framework to include social and economic impacts into the EIS process, and can further integrate stakeholder involvement in a wide array of public land decisions.

7. Soil erosion threatens the sustainability of rangelands. Concentrated flow erosion processes are distinguished from splash and sheet flow processes in their enhanced ability to mobilize and transport large amounts of soil, water and dissolved elements off-site impacting soil health and sustainability of the site. A team of ARS scientists in Reno, Nevada, in association with ARS scientists in Tucson, Arizona, and Boise, Idaho, have developed a new risk assessment tool to assess potential soil loss. This new tool allows land managers the ability to assess the sustainability of the site as compared to the historic plant community of the site. With this new information and utilizing the Rangeland Hydrology and Erosion Model (RHEM), managers are provided with a simple and accurate tool to rapidly assess and establish priorities for determining which areas need conservation.

8. The native Great Basin shrub ephedra adapts to climate change by altering seed size. There is concern regarding the ability of long-lived plants to respond to the increasing stress imposed by climate change. Collaborating with a doctoral student at the University of Nevada, ARS scientists in Reno, Nevada, studied the long-lived native shrub Mormon tea (Ephedra viridis). The purpose of this research was to quantify transgenerational phenotypic plasticity, a mechanism allowing rapid response to environmental change, of Ephedra in response to potential future climate change. Ephedra growing in areas with greater average climatic stress produced more massive seeds than those from more temperate areas. Ecological/evolutionary theory predicts that increased seed size will allow long-lived plants to increase survivability in a future drier climate.

9. Holistic grazing system increases soil carbon and nitrogen. ARS scientists in Reno, Nevada, collaborated with a range consultant and completed research on the effect of two grazing management systems (traditional vs. holistic), on soil properties in New Mexico. Traditional grazing, as practiced in this area of New Mexico, is typically year-round with a stocking rate of one cow per fifty-six acres. This holistic system greatly increased the number of pastures so cattle graze each for only three to five days and then pastures are rested for hundred days. Using the holistic system, the rancher is now stocking one cow per thirty-five acres. For each grazing system, soils were sampled by depth (0-4, 4-8 inches) and microsite (bare ground, grass, and shrub). Overall, rangelands managed using holistic principles, had significantly greater total soil nitrogen and total soil carbon than traditionally grazed rangelands and the proportion of bare ground decreased, increasing forage production and resulting in greater stocking capacity.


Review Publications
Blank, R.R., Morgan, T.A. 2016. Interactions with soils conditioned by different vegetation: a potential explanation of bromus tectorum L. invasion into salt-deserts? Journal of Arid Environments. 124:233-238.
Smith, A.M., Talhelm, A.F., Kolden, C.A., Newingham, B.A., Kremens, R.L., Adams, H.D., Cohen, J.D., Yedinak, K.M. 2016. The ability of winter grazing to reduce wildfire size, intensity, and fire-induced plant mortality was not demonstrated: a comment on Davies et al. (2015). International Journal of Wildland Fire. doi: 10.1071/WF15163
Clements, D.D., Harmon, D.N., Young, J.A., Blank, R.R. 2016. Phenology of cheatgrass and associated exotic weeds. The Progressive Rancher. 16(5):8-9.
Harmon, D.N., Clements, D.D. 2015. The importance of seed germination in rangeland research. The Progressive Rancher. 15(7):24-25.
Longland, W.S., Dimitri, L.A. 2016. Are western juniper seeds dispersed through diplochory? Northwest Science. 90(2):235-244.
Weltz, M.A., Nouwakpo, S.K., Hernandez, M., Nearing, M.A., Stone, J.J., Armendariz, G.A., Pierson, F.B., Al-Hamdan, O., Williams, C.J., Spaeth, K.F., Wei, H., Heilman, P., Goodrich, D.C. 2015. USDA internet tool to estimate runoff and soil loss on rangelands: rangelands hydrology and erosion model. The Progressive Rancher. 8:24-25.
Nouwakpo, S.K., Williams, C.J., Al-Handan, O., Weltz, M.A., Pierson, F.B., Nearing, M.A. 2016. A review of concentrated flow erosion processes on rangelands: fundamental understanding and knowledge gaps. International Soil and Water Conservation Research. 4(2):75-86.
Williams, C.J., Pierson Jr, F.B., Spaeth, K.E., Brown, J.R., Al-Hamdan, O.Z., Weltz, M.A., Nearing, M.A., Herrick, J.E., Boll, J., Robichaud, P.R., Goodrich, D.C., Heilman, P., Guertin, P.D., Hernandez, M., Wei, H., Hardegree, S.P., Strand, E.K., Bates, J.D., Metz, L., Nichols, M.H. 2016. Incorporating hydrologic data and ecohydrologic relationships in ecological site descriptions. Rangeland Ecology and Management. 69:4-19.
Clements, D.D., Freese, M., Scott, M., Harmon, D.N. 2016. Importance of shrub restoration on great basin rangelands. The Progressive Rancher. 16(6):8-10.
Cadaret, E.M., Mcgwire, K.C., Nouwakpo, S.K., Weltz, M.A., Saito, L. 2016. Vegetation canopy cover effects on sediment erosion processes in the upper Colorado River Basin mancos shale formation, Price, Utah. Catena. 147:334-344.
Cadaret, E.M., Nouwakpo, S.K., Mcgwire, K.C., Saito, L., Weltz, M.A., Blank, R.R. 2016. Experimental investigation of the effect of vegetation on soil, sediment erosion, and salt transport processes in the Upper Colorado River Basin Mancos Shale formation, Price, Utah, USA. Catena. 147:650-662.
Weltz, M.A., Morris, C., Badik, K.J., Morris, L.R. 2016. Integrating precipitation, grazing, past effects and interactions in long-term vegetation change. Journal of Arid Environments. 124:111-117.
Weltz, M.A., Nouwakpo, S.K., Mcgwire, K. 2016. Performance of the rangeland hydrology and erosion model for runoff and erosion assessment on a semiarid reclaimed construction site. Journal of Soil and Water Conservation. 71:220-236.