Location: Great Basin Rangelands Research2013 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. Hypotheses: 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 studieswill 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). Ojective 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. Hypotheses: 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 first report for the new project that began in June of 2013 by Great Basin Rangelands Research Unit (GBRRU) in Reno, Nevada, and continues research from 5370-11220-006-00D, "Integrated Invasive Species Control, Revegetation,and Assessment of Great Basin Rangelands". GBRUU undertakes basic and applied research to improve the health and sustainability of Great Basin rangelands. New herbicidal control methodologies, applied this year, have significantly reduced competition from exotic annual grasses including cheatgrass. Incorporating new plant materials into the seeding program, such as kochia, have increased forage availability even during periods of drought. Basic research into how cheatgrass invasion affects soil carbon and nitrogen cycling indicates greater quantities of labile carbon (carbon that mineralizes quickly) suggesting faster turnover of carbon. We are studying potential uses of biochar in ameliorating deleterious soil conditions and as a germination enhancer for seeds. We are cooperating in an international study to decipher why exotic annual grasses, such as medusahead, are highly invasive in western North America; yet, not nearly as invasive in Eurasia, where they evolved. GBRUU is cooperating with the Pasture Systems and Watershed Management Unit, ARS, University Park, Pennsylvania, on a carbon sequestration project. The unit has studied if soil manganese availability is affected by cheatgrass invasion. Soils invaded by cheatgrass have greater pools of manganese in the top 10 cm compared to paired non-invaded areas. Tree coring was conducted to determine tree age for 100 western juniper trees at 2 field sites in Northeast California, which will be used to determine the age structure of each juniper population. Production of seedproducing female cones (aka, “berries”) was also counted or estimated for these trees, and a sample of 100 juniper berries was collected from 20 trees at each site and dissected in the laboratory to quantify insect infestations that affect seed viability in western juniper. To date, we have identified more than 30 insect species 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. GBRRU scientists in collaboration with the National Agricultural Library, Bureau of Land Management, and University of Nevada, Reno, initiated a project to improve the understanding of sources and transport mechanisms of dissolved solids (salts) from rangelands. The team has conducted an extensive international literature review and will publish an annotated bibliography and synthesis report later this year. This work has resulted in the Bureau of Reclamation funding a new project to quantify soil loss and salinity transport from western rangelands to enhance the ability to conduct national assessments of soil loss on western rangelands. The aim of this project is to determine cost effective means of enhancing degraded rangelands and reducing salinity and sedimentation in western rivers.
1. New tools are available to reduce cheatgrass impacts. The failure to successfully rehabilitate degraded Great Basin rangelands dominated by cheatgrass threatens the multiple uses demanded of these rangelands from healthy wildlife populations (i.e. sage grouse) to sustainable agriculture (i.e. livestock grazing). Scientists at the Great Basin Rangelands Research Unit, Reno, Nevada, tested 3 separate herbicides for their ability to control cheatgrass. One of the evaluated herbicides resulted in a 98.7% reduction in cheatgrass. Our ability to successfully control cheatgrass with tested herbicides has improved the success of the establishment of seeded species through proper applications and timing methodologies. This measurable success of establishing long-lived perennial bunchgrasses and shrubs has decreased the fuel dangers associated with cheatgrass by decreasing cheatgrass densities by as much as 99%.
2. Restoring sagebrush habitat to meet wildlife and livestock needs. The Great Basin has undergone more environmental change in the last 250 years than it has since the close of the last ice age. One of the big drivers of this change is the introduction of the introduced specie cheatgrass. Scientists at the Great Basin Rangelands Research Unit, Reno, Nevada, seeded and transplanted big sagebrush at two locations in northern Nevada to monitor success and cost-effectiveness in big sagebrush restoration practices that had been invaded by cheatgrass. The take home message from these experiments is that seeding of sagebrush is not cost-effective; rather, transplanting of sagebrush is cost-effective on critical sites and does result in desirable stands of sagebrush.
3. Novel ways to suppress invasive annual grasses are now being developed based on understanding competition. The key to long-term rehabilitation of cheatgrass-degraded rangelands is establishing perennial grasses that will suppress cheatgrass. Mechanistic understanding of suppression is lacking. The experimentation suggests that established perennial grasses reduce soil nitrogen (and possibly phosphorus) to levels such that growth of cheatgrass is negatively affected. The research also suggests that exudation of chemicals from established perennial grasses reduce root hair formation, likely reducing nutrient uptake of cheatgrass. ARS researchers in Reno, Nevada, are presently attempting to identify suspect chemicals. This basic research suggests that selection of perennial grasses most capable of suppressing cheatgrass may involve their ability to lower surface soil nitrogen availability.
4. Biochar can improve soil health. Pinyon-juniper expansion in the Great Basin has reduced herbaceous vegetation necessary for livestock and wildlife. The cost of tree removal, to rehabilitate rangelands, can be offset by producing biochar from the trees. The Reno Great Basin Rangelands Unit, Reno, Nevada, is presently evaluating biochar from juniper as a seed germination enhancer and to ameliorate salt-affected soils. Data are preliminary, but in greenhouse studies, addition of biochar to salt-affected soil does increase the growth of several test grasses. More research is needed to determine optimal rates of biochar addition.