Location: Great Basin Rangelands Research2015 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.
This is the third annual report for project 2060-13610-001-00D 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 years of below normal precipitation. Earlier this year, U.S.D.A. declared most of Nevada a natural disaster area due to lingering drought. Feed for livestock is scarce and irrigation water has been severely curtailed thus affecting the economic viability of many ranchers and farmers. The extended drought has impacted GBRRU field experiments and some milestones could not be met due to poor seed germination and minimal plant growth. 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. Sub-objective 1.1: The GBRRU progressed by conducting DNA sequencing runs on plants collected from 5 of 14 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 SSR (i.e., single sequence repeat) markers spread throughout the cheatgrass genome. Sequencing runs are being analyzed with GENIOUS software, identifying hundreds of SNPs (single nucleotide polymorphisms) and SSRs. DNA extraction and PCR amplification have been conducted for each of the 14 sampled populations. Sub-objective 1.2: Progress was made through experiments conducted in Northeast California. We quantified removal rates of western juniper berries and seeds by animals. Trail cameras focused on juniper berries and seeds used in field experiments to identify numerous 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. With the hiring of a new scientist, the GBBRU made progress in sub-objective 1.3. In a field experiment, we examined the effects of climate change (drought and warming) on sagebrush steppe communities in the Great Basin at five burned sites. We established control, drought, warming, and drought + warming plots and seeded two native perennial grasses used in post-fire rehabilitation and the exotic invasive annual grass cheatgrass. Native grass emergence was low in drought and warmed plots. However, warming increased native grass height and specific leaf area. Cheatgrass emerged in all treatments, but drought and warming negatively affected cheatgrass biomass, plant height, and specific leaf area. Our results suggest that native and non-native species may respond differently to future climate change. Objective 2: We have made progress both in understanding the long-term effects of wildfire on soil nutrient availability and watershed processes. This past year, we quantified soil nutrient availability and plant nutrient content, spatially and temporally, following a wildfire in a sagebrush ecosystem. Surface soil in burned sagebrush canopies had elevated nutrient levels over one year following the wildfire. Pinyon and juniper expansion have significantly altered the hydrology and sustainability of Great Basin rangelands. GBRRU scientists have made progress in understanding the benefits of conservation treatments to remove pinyon and juniper woodlands in joint research with ARS scientists in Boise, Idaho. We have found that treatments that increase ground cover can significantly reduce surface runoff and soil erosion while also reducing the density of invasive annual grasses. Scientists at the GBRRU continue to make progress in understanding the physio-chemical mechanisms by which perennial grasses suppress annual grasses, sub-objective 3.1. Long-term field studies combined with greenhouse projects have shown that established perennial grasses reduce soil nitrogen availability and occupy biological soil space thereby severely limiting the growth of cheatgrass. Ongoing field studies are measuring differences in soil properties between rings of cheatgrass suppression around established perennial grasses and areas not suppressed. These data fit into a paradigm developed at GBRRU that cheatgrass has the ability to “engineer” the soil to increase the availability of soil nitrogen and phosphorus, and thereby increase its competitive potential. A new greenhouse study is quantifying cheatgrass suppression as a function of distance from established crested wheatgrass. We are also making progress in the understanding of how climatic variability affects cheatgrass. In field studies, researchers at the GBRRU are studying the role of increased precipitation in facilitating the growth and density of cheatgrass in the absence of and in the presence of established perennial grasses. Sub-objective 3.2: Researchers with the GBRRU are testing mechanical weed control practices along with plant material testing and seeding methodologies at a cheatgrass infested habitat in northern Nevada. Mechanical weed control practices before cheatgrass seed maturity reduced cheatgrass seed bank densities from 69-87%. The introduced perennial grass, Siberian wheatgrass, the introduced semi-shrub, ‘Immigrant’ forage kochia, and the native perennial grass, Sandberg bluegrass, are well-suited to suppress cheatgrass. The combination of active weed control with conservation seeding resulted in a 870% reduction in cheatgrass density and decreased cheatgrass fuel loads from 2,069 lbs/acre to 148 lbs/acre, a 930% reduction in fine fuels. The conversion of formerly big sagebrush/bunchgrass communities to annual grass dominance, has sparked an increasing demand to re-establish big sagebrush/bunchgrasses. Seeding Wyoming big sagebrush is largely unsuccessful; therefore, transplanting big sagebrush has become more popular. We conducted research at two separate sites in northwestern Nevada where we compared fall versus spring transplanting of Wyoming big sagebrush into crested wheatgrass stands. Fall transplanting experienced 46-62% survivability while spring transplanting experienced 13-34% survivability. Precipitation in the fall to winter months (October-March) contributes to the significantly higher success of Wyoming big sagebrush fall transplants experienced in northwestern Nevada. We continue to make progress on how desert rodents impact specific plant species and on species composition of arid plant communities. 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. 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, given the ability of Indian ricegrass seeds to endure long periods of dormancy, we will sample for seedlings again in 2016. We have made progress on sub-objective 4.1 as GBRRU scientists, working with ARS scientists in Tucson, Arizona, and Boise, Idaho, together developed and transferred the Rangeland Hydrology and Erosion Model (RHEM) to the Bureau of Land Management (BLM) and Natural Resources Conservation Service (NRCS). Additionally, both agencies are actively working to have the model available for cost-effective conservation planning activity by 2016. GBRRU scientists working with collaborators have developed a framework for inclusion of key ecohydrologic feedbacks using the Rangeland Hydrology and Erosion Model for inclusion into Ecological Site Descriptions (ESDs) and thereby enhance 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 have made progress on sub-objective 4.2 involving assessment of 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 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, and (4) evidence of an equilibrium channel geometry with a given discharge that is marginally impacted by runoff duration.
1. The Lawson Aerator. Degraded big sagebrush/bunchgrass communities in the Great Basin severely reduces grazing resources and habitats for cattle and wildlife. ARS scientistsin Reno, NV mechanically treated old decadent big sagebrush habitats in north-central Nevada using a Lawson Aerator. Pulled by a tractor, the Lawson Aerator consists of a heavy drum with blades that crushes decadent vegetation, and reduces soil compaction thereby aerating the soil. Prior to this mechanical treatment, the decadent big sagebrush cover was over 40% and the presence of desirable herbaceous vegetation was nearly absent (1.3 plants m-²). In the spring of 2015, the treated habitat yielded 8.7 perennial grasses and 3.4 perennial forbs m-² with a big sagebrush cover of 5%. This innovative treatment has provided excellent wildlife and grazing values to the area.
2. Bibliography of Salinity. ARS scientists in Reno, Nevada, the National Agricultural Library (NAL) and the Bureau of Land Management developed a worldwide bibliography (available on-line at NAL). It is a guide to the scientific literature covering salinity sources, mobilization, and transport from rangelands to river systems, with particular emphasis on the Colorado River Basin. The bibliography provided the information for literature synthesis on salinity transport from rangelands and how management/conservation practices may alter dissolved salt transport. The Bureau of Land Management and Bureau of Reclamation are using these documents to direct a multimillion dollar, multiyear research effort to develop cost-effective conservation practices to reduce salt loading within the Colorado River Basin.
Al-Hamdan, O.Z., Hernandez, M., Pierson Jr, F.B., Nearing, M.A., Williams, C.J., Stone, J.J., Boll, J., Weltz, M.A. 2014. Rangeland Hydrology and Erosion Model (RHEM) enhancements for applications on disturbed rangelands. Hydrological Processes. doi: 10.1002/hyp.10167.
Blank, R.R., Morgan, T.A. 2014. Does a trend in declining stem density of Lepidium latifolium indicate a phosphorus limitation? A case study. Invasive Plant Science and Management. 7:526-531.
Blank, R.R., Morgan, T.A., Allen, F.L. 2015. Suppression of annual Bromus tectorum by perennial Agropyon cristatum: roles of soil N availability and biological soil space. AoB Plants. 7:plv006. doi: 10.1093/abpia/plv006.
Clements, D.D., Harmon, D.N., Weltz, M.A., Blank, R.R., Henderson, D.E. 2015. Assessment of horse creek conservation seeding. The Progressive Rancher. 15(2):35-37.
Clements, D.D., Harmon, D.N., Young, J.A., Knight, J. 2015. An integrated approach to salt cedar control and rehabilitation. The Progressive Rancher. 15(5):36-37.
Dimitri, L.A., Tonkel, K.C., Longland, W.S., Rector, B.G. 2014. The insect microcosm of western juniper berries. Rangelands. 36(3):8-11.
Jones, R., Chambers, J.C., Johnson, D.W., Blank, R.R., Board, D.I. 2014. Effect of repeated burning on plant and soil carbon and nitrogen in cheatgrass (Bromus tectorum) dominated ecosystems. Plant and Soil. 386:47-64.
Jones, R.O., Chambers, J.C., Board, D.I., Johnson, D.W., Blank, R.R. 2015. The role of resource limitation in restoration of sagebrush ecosystems dominated by cheatgrass (Bromus tectorum). Ecosphere. 6(7):107.
Longland, W.S. 2014. Biological control of saltcedar (Tamarix spp.) by saltcedar leaf beetles (Diorhabda spp.): effects on small mammals. Western North American Naturalist. 74(4):378-385.
Spaeth, K., Weltz, M.A., Briske, D., Jolley, L.J., Metz, L.J., Rossi, C.G. 2013. Rangeland CEAP: An assessment of conservation practices. Rangelands. 35:2-10.
Weltz, M.A., Jolley, L., Hernandez, M., Spaeth, K., Rossi, C., Talbot, C., Nearing, M.A., Stone, J.J., Goodrich, D.C., Wei, H., Pierson Jr, F.B., Morris, C.E. 2014. Estimating conservation needs for rangelands using USDA National Resources Inventory Assessments. American Society of Agricultural and Biological Engineers. 57(6):1-12.
Weltz, M.A., Nouwakpo, S.K., James, M.R., Huang, C., Chagas, I. 2014. Evaluation of structure from motion for soil microtopography measurement. The Photogrammetric Record. 29(147):297-316.