Location: Great Basin Rangelands Research2020 Annual Report
The long-term objective of the Great Basin Rangelands Research Unit (GBRRU) project plan is to facilitate sustainability of ecosystem goods and services provided by arid rangelands with a focus on production of forage for domestic grazing animals, conservation and restoration of these rangelands, and maintaining or enhancing ecosystem processes that facilitate desired plant communities. This will be approached by addressing critical research needs affecting arid and semi-arid rangelands, including: (1) investigating the ecology and control of invasive weeds, (2) rehabilitating degraded rangelands, (3) maintaining and enhancing productive rangelands, and (4) quantifying impacts of management practices. The project will integrate basic research on Great Basin rangelands with new tools, plant materials, and technologies to reduce the spread of invasive and expanding plant populations and assess effectiveness of management practices. Specifically, during the next five years we will focus on the following objectives. Objective 1: Develop tools and strategies for maintaining and enhancing the sustainability of arid rangeland ecosystems based on an improved understanding of soil properties, plant-soil relationships, and alternative management practices. (NP215 1A, 3B, 4A) Subobjective 1A: Quantify salt mobility and transport as a function of rainfall return period on saline rangeland soils, and parameterize the Rangeland Hydrology and Erosion Model (RHEM) for estimating runoff, sediment yield and salt transport. (Weltz) Subobjective 1B: Quantify vulnerabilities to soil erosion on non-federal rangelands as part of a national assessment in collaboration with NRCS. (Weltz, Newingham) Subobjective 1C: Investigate effects of post-expansion piñon and juniper tree control and exclusionary fencing on components of the water budget and recovery of sagebrush steppe and meadow habitats and assess weather variability and impacts on plant phenology. (Snyder) Subobjective 1D: Apply bioinformatic analyses to newly developed single-nucleotide polymorphism (SNP) markers to determine whether outcrossing and heterosis in cheatgrass may facilitate invasion of new environments in Great Basin ecosystems. (Longland) Objective 2: Evaluate rangeland community productivity, responses to disturbance, and identify appropriate rehabilitation practices. (NP215 1A, 3B, 4A) Subobjective 2A: Assess effects of post-fire grazing on burned rangelands. (Newingham) Subobjective 2B: Quantify effects of arthropod seed predators in reducing seed viability of western and Utah juniper as a potential pre-establishment control strategy. (Longland) Subobjective 2C: Develop management strategies providing guidelines and tools to stakeholders for enhancing native grass productivity on Great Basin rangelands using diversionary seeding. (Longland)
Subobjective 1A, Hypothesis: Runoff, sediment yield, and salt transport processes will increase as a non-linear function of rainfall return period through rill processes being initiated. Rainfall simulations will be conducted to quantify salt mobility and transport as a function of rainfall return period on saline rangeland soils and to parameterize the Rangeland Hydrology and Erosion Model. Subobjective 1B, Research Goal: Quantify rangeland vulnerability to soil erosion. Unit scientists and a team from the National Agricultural Library will develop the Agricultural Runoff Erosion and Salinity database. They will also expand the current understanding of wind erosion processes in the Great Basin by establishing a new post-fire National Wind Erosion Research Network site in eastern Nevada. These research activities will allow users to quantify vulnerabilities to soil erosion on rangelands. Subobjective 1C, Hypothesis: Mechanical tree control treatments for piñon and juniper will reduce precipitation interception and tree transpiration losses and result in increased soil moisture, which will increase the presence and diversity of the desired understory vegetation. Ecological and hydrological instrumentation will be used at a field station in central Nevada to: (1) investigate effects of post-expansion piñon and juniper tree control and exclusionary fencing on components of the water budget and recovery of natural habitats, and (2) assess weather variability and impacts on plant phenology. Subobjective 1D, Hypothesis: Occasional outcrossing facilitates expansion of cheatgrass across the intermountain west by selecting for new genotypes adapted to drier sites and more alkaline soils. Bioinformatic analyses will be applied to newly developed single-nucleotide polymorphism (SNP) markers in order to determine whether outcrossing and heterosis in cheatgrass may facilitate invasion of new environments in Great Basin ecosystems. Subobjective 2A, Hypothesis: Delaying defoliation at least two years post-fire will ensure adequate perennial grass establishment. Defoliation experiments with native perennial grass species will be conducted to assess effects of post-fire grazing on burned rangelands. Subobjective 2B, Hypothesis: Arthropods that feed on juniper seeds vary systematically in their quantitative impacts in rendering seeds inviable. Systematic sampling of juniper berries from several field sites and laboratory dissection of the berries to identify associated arthropods will be used to quantify effects of arthropod seed predators in reducing seed viability of western and Utah juniper as a potential pre-establishment control strategy. Subobjective 2C, Hypothesis: Manipulating the behavior of granivorous rodents through the addition of preferred diversionary seeds to field plots enhances seedling recruitment of Indian ricegrass. Using commonly available commercial seeds, seed augmentation experiments intended to manipulate the behavior of seed-caching rodents (i.e., “diversionary seeding”) will be conducted to develop management strategies for enhancing native grass productivity on Great Basin rangelands.
In support of Sub-objective 1A, research was focused on how salinity in rivers affects every aspect of life from drinking water to industrial and agricultural use. The Upper Colorado River has natural and anthropogenic sources of salinity. Researchers at ARS developed a project with University of Nevada, Reno (UNR), Desert Research Institute (DRI), and Bureau of Land Management (BLM) colleagues to develop new predictive tools to assess risk of salt transport during storm flow at hillslope and watershed scales. The team evaluated nine sites in Utah and Colorado, developing predictive equations to quantify salt loading and salt transfer across the land as a function of storm intensity. The team developed methods to assess which watersheds in the Upper Colorado River Basin had the highest risk for contributing salt loading to the Colorado River. This enabled tracking of salt redistribution into the soil during a rainfall event and partitioning remaining salt that was available to be transported overland and potentially reach the river. Woody species encroachment into herbaceous and shrub-dominated rangelands is a worldwide concern. Woody species lead to changes in vegetation structure and altered biophysical processes. Encroachment of pinyon (Pinus spp.) and juniper (Juniperus spp.) tree species into sagebrush-steppe environments threatens typical hydrological functioning of these ecosystems. Prescribed fire has been proposed as one rangeland improvement practice to restore sagebrush-steppe from pinyon-juniper encroachment. Short-term effects of burning on the hydrologic response of these systems have been documented and often include a period of increased erosion vulnerability. Long-term hydrologic responses of sagebrush-steppe ecosystems to fire are poorly understood. A team of ARS scientists evaluated vegetation, hydrologic, and erosion responses at two pinyon-juniper encroached sagebrush sites nine years after prescribed fire was applied as a restoration treatment. Overall, increases in herbaceous cover in intercanopy areas between trees at both sites resulted in a 6.5 – 7.6-fold reduction in runoff and erosion depending on vegetation regrowth and initial level of degradation. Results indicate that prescribed fire can be used cautiously to restore hydrologic function in degraded rangelands where woody species have been removed. To address Sub-objective 1B, the ARS team developed new approaches of estimating rainfall storm events, allowing development of gridded climate files for better prediction of runoff, soil erosion, sediment transport and water quality in the western United States. These tools will allow BLM and Natural Resources Conservation Service (NRCS) and landowners to understand where landscape conservation and salt load management practices could be implemented to reduce salt transport into the Colorado River. Sub-objective 1B also involves post-fire wind erosion. Fire not only affects water erosion but also wind erosion due to exposed soil for several months after fire. However, little information exists about effects of fire on wind erosion. In collaboration with BLM, we have installed two wind erosion sites (Twin Valley and Red Hills) associated with the National Wind Erosion Network (NWERN). These sites are located on the Martin Fire, which burned in July 2018. Measurements include temperature, relative humidity, precipitation, wind speed and direction, saltation, dust flux, soil particle size distribution, soil surface roughness, aggregate size distribution, biological soil crust, and vegetation. Additionally, equipment was installed at Twin Valley to measure concentrations of particulate matter smaller than 2.5 microns (PM 2.5), which can get into lungs. Soil samples were collected monthly when sites were accessible. Vegetation and soil surface characteristics were measured three times in the past year. Ecohydrological data collection in the Porter Canyon Experimental Watershed (PCEW) in the Desatoya Mountain Range is now in its tenth year, with the goal to develop tools and strategies for arid rangeland ecosystems based on an integrated understanding of plant and soil relationships. This research addresses Sub-objective 1C to determine effects of tree control in recently expanded woodlands on components of the water budget and understory plant community response. BLM masticated 105 acres of pinyon and juniper woodlands above the instrumentation in PCEW in Fall 2019. We continue to collect data on soil moisture, soil temperature, plant phenology, spring flow, groundwater levels, streamflow, and plant community composition. Additional funds from BLM were used to instrument several high elevation meadows in the Desatoya Mountains. This instrumentation enhances progress on Sub-objective 1C, to understand meadow responses to controlled grazing and use phenology cameras to quantify plant phenological responses under variable environmental conditions. Over-grazing by cattle and wild horses can lead to groundwater declines and degradation of meadow habitat. Meadow habitat is critical to the survival of sage grouse chicks. The BLM and Nevada Department of Wildlife installed exclusionary fencing in three of the four meadows this fall. We finished instrumentation of four high elevation meadows with plant phenology cameras, weather stations, snow depth sensors and soil moisture sensors. We now have six paired camera stations in three meadows that have grazed and un-grazed areas and a seventh camera station in an unfenced control meadow. This is a fully replicated grazing experiment to determine the effects of exclusionary fencing on: meadow species composition, timing and peak of plant greenness, and changes in soil moisture. Field measurements of plant phenology and species composition are now in the third year. In support of Sub-objective 1D, DNA sequencing was conducted on cheatgrass samples collected from sites throughout the Great Basin and Mojave regions and from several European populations within the native range of the plant. Two scientists with ARS, Reno, Nevada, collaborated with a UNR bioinformatics specialist to analyze sequencing data using DNASTAR Lasergene software and generate single nucleotide polymorphism (SNP) markers for characterizing specific cheatgrass genotypes. Marker data will be used in both a longitudinal (time-series) study of genetic changes within a population and in a snapshot study comparing genotypic frequencies among numerous populations. Analyses using these SNPs will improve our understanding of cheatgrass invasion processes and help direct searches for effective biocontrol agents by identifying native range origins of U.S. cheatgrass populations. Native perennial bunchgrasses are often seeded and domestic livestock grazing is often delayed two growing-seasons after wildfire in the Great Basin. Seeding failures often occur due to unsuitable abiotic conditions or inappropriate post-fire management. In support of Sub-objective 2A, we established an experiment examining how neighboring plant communities and timing of post-fire defoliation affect post-fire seeding treatments in Artemisia tridentata ssp. wyomingensis communities in northwest Nevada and southeast Oregon. Plant removal treatments varied the relative density of adult and seedling perennial bunchgrasses, while spring and fall defoliation treatments simulated livestock grazing. We recorded within-season timing of senescence, leaf and inflorescence production, and stem length, as well as across-season bunchgrass density, foliar cover, and seedling survival. Our results will inform managers on whether post-fire plant community structure affects restoration efficacy, and whether spring and fall defoliation differ in their effects on seedling perennial bunchgrasses. Progress on Sub-objective 2B included sampling of juniper berries at three western juniper sites in northern California and at five Utah juniper sites in western and central Nevada. In the lab we dissected at least 100 berries per tree from 20 trees per site and collected larvae from insect species that damage juniper seeds, as well as reared adult arthropods from mass berry collections. To date, we have identified 38 insect species and one mite species that occur within western juniper berries, at least seven of which are seed predators that render seeds inviable. The recent expansion of this work to include Utah and California juniper is generally finding the same or closely related seed predators in berries of these species. This research will determine if arthropod damage to juniper seeds is primarily accomplished by one or a few species or is attributable to a greater variety of species. This is an essential first step for potential biological control applications, and it has immediate utility for parameterizing models of juniper expansion. Progress on Sub-objective 2C was limited by mandatory telework. Collectively, desert rodent species constitute the most important consumers of seeds on arid western rangelands. Some rodents also provide important seed dispersal benefits to certain plants through seed caching activities. The diversionary seeding concept involves broadcasting inexpensive, commercially available seeds (i.e., “diversionary” seeds) to reduce the rate that granivorous rodents consume seeds of an alternate plant species that is a target for restoration efforts. This approach has been previously demonstrated to be successful for enhancing seedling productivity of Indian ricegrass, an important forage grass for livestock on Great Basin rangelands. A broadcast seeding experiment was initiated in October 2019 at two western Nevada study sites. However, an experiment involving use of diversionary seeds in conjunction with drill seeding was to be initiated in March 2020, but was prevented by mandatory telework due to the COVID-19 pandemic. This experiment will therefore be delayed for one year.
1. Quantifying watershed scale salt loading. The Colorado River has significant challenges in meeting international treaties on water quality with Mexico. ARS scientists in Reno, Nevada, and Kimberly, Idaho, along with scientists at the Desert Research Institute (DRI) developed an approach to use the Rangeland Hydrology and Erosion Model to estimate soil erosion and salt loading at the hillslope and watershed scale. These tools will allow the Bureau of Land Management (BLM), the Natural Resources Conservation Service (NRCS), and landowners to understand where the landscape conservation and salt load management practices could be implemented to reduce salt transport. This will also facilitate improved water quality for the Colorado River, which provides a large portion of the water supply for the western United States.
2. Climate influence on soil erosion. Soil erosion and runoff on arid and semi-arid rangelands is driven by precipitation intensity and duration. Currently there are relatively few weather stations in the western United States with sufficient measurements of these precipitation parameters to estimate runoff and soil erosion at the hillslope scale across the west. ARS scientists in Tucson, Arizona, and Reno, Nevada, developed new ways to estimate these critical parameters from alternative weather records. The team now has methods to estimate these climate parameters and predict risk of soil loss on rangelands worldwide at a scale that is appropriate for making management decisions.
3. Qualitative assessment tool for rangeland health. Rangeland health assessments are critical to maintaining ecosystem productivity under the pressures of livestock grazing, fire, invasive species, and other disturbances. An ARS scientist in Reno, Nevada, in collaboration with instructors from the Bureau of Land Management (BLM), U.S. Geological Survey, U.S. Forest Service, and Natural Resource Conservation Service (NRCS) have updated and published a technical document on the qualitative assessment tool for rangeland health, “Interpreting Indicators of Rangeland Health” (IIRH). Changes incorporated in the IIRH, Version 5 are designed to improve the ease of using the protocol in the field and clarify instructions. The IIRH protocol is the standard for BLM and NRCS rangeland health assessments and is applied domestically on over 500 million acres of U.S. rangelands. The protocol has been published in four languages and implemented internationally in at least five countries. It is used by private landowners and livestock producers, as well as by organizational planners and researchers.
4. Comprehensive synthesis of the state of the knowledge in pinyon and juniper woodlands. A researcher for ARS Reno, Nevada, worked with a team of researchers from other ARS locations, U.S. Forest Service, U.S. Geologic Survey, and University collaborators to synthesize recent research findings and comprehensively summarize the current knowledge of pinyon and juniper ecosystems in a General Technical Report for managers, researchers, and the interested public. The ecohydrology section discusses hydrologic processes in woodlands that influence soil conservation and loss; water capture, release and storage; and the effect of woodland structure and composition on these processes. Key components in the success or failure of restoration and management activities are discussed - components that are necessary to consider when restoring ecosystem function and resilience. This publication was well-received by the management community as evidenced by the large number of downloads, was the topic of a press release, and was selected by the U.S. Forest Service to be featured in a “Science You Can Use” Bulletin.
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