Location: Great Basin Rangelands Research2021 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.
Sub-objective 1A involves developing several key USDA publications. The Rangeland Erosion Assessment and Watershed Protection Team developed science-based tools for assessing rangeland condition. The team assisted in developing the USDA National Range and Pasture Handbook 645 to address rangeland ecohydrology. As part of national policy, the Natural Resources Conservation Service (NRCS) adopted the Rangeland Hydrology Erosion Model (RHEM) and mandated its use with release of the handbook in 2021. To support new USDA requirements the team developed USDA Handbook 646 (Rangeland Processes: Hydrology and Soil Erosion) to describe basic processes and literature regarding soil erosion on rangelands. They developed USDA Handbook 647 (Rangeland Hydrology and Erosion Handbook: The RHEM Guide), which describes equations used by the tool and provides a complete user guide and tutorial with four examples – wildfire, invasive plants, overgrazing and conservation benefits. These handbooks, plus an additional 25 publications, were used for a five-day in-person NRCS short course on ecohydrologic processes. This provides instruction on using the RHEM Model (https://dss.tucson.ars.ag.gov/rhem/) for assessing sustainability of rangelands as a function of return period runoff events and includes a newly developed application of risk management. The team developed YouTube videos (https://www.youtube.com/watch?v=AvDPRyU_PZE ) and AgLearn style training on RHEM and Automated Geospatial Watershed Assessment (AGWA) (https://www.tucson.ars.ag.gov/agwa/) for use when in-person training is not available. In-person training workshops are taught twice a year (virtually during the pandemic), and training has been translated into French, Arabic, Russian and Spanish. This enables RHEM to be used across the globe in arid and semi-arid rangelands to address sustainable food and water security issues through promoting productive rangelands, conservation planning, and protection of natural resources after wildfire. Runoff water quality assessment of rangeland areas treated with compost was suspended due to travel restrictions, but will resume in 2022. Sub-objective 1B involves wind and water erosion. Fire not only affects water erosion and watershed processes but also affects wind erosion due to exposed soil. Little information exists about effects of fire on wind erosion. In collaboration with the Bureau of Land Management (BLM), we installed two-wind erosion sites associated with the National Wind Erosion Network (NWERN). These sites are located in Northern Nevada where the Martin Fire 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. Soil samples were collected monthly when sites were accessible. Vegetation and soil surface characteristics were measured three times in the past year. Data has been submitted to the NWERN database, and research collaborations have been facilitated through monthly meetings. Ecohydrological data collection in the Porter Canyon Experimental Watershed (PCEW) in the Desatoya Mountain Range is now in its 11th year to develop tools and strategies for arid rangeland ecosystems based on an integrated understanding of plant and soil relationships. Progress has been made on Sub-objective 1C, research to determine the effects of tree control in recently expanded woodlands on components of the water budget and understory plant community response. The BLM is continuing to remove trees this summer and fall, while ARS continues to collect data on soil moisture, soil temperature, plant phenology cameras, spring flow, groundwater levels, streamflow, and plant community composition. Upland vegetation community composition was measured in both cut and uncut plots in Summer 2020. Once pinyon and juniper are removed, mountain mahogany previously in the understory becomes more dominant. We have selected two sites where we will install sap flow probes on mountain mahogany to determine water requirements of this species with and without a pinyon/juniper overstory. We collected tree cookies from both pinyon and juniper trees in late fall 2019, however due to COVID-19 restrictions we did not yet prepare them for isotopic sampling. We will reschedule this for Fall of 2021. Upper elevation meadows in Haypress have been fully instrumented for two full growing seasons. Baseline data on plant composition and phenology with no grazing exclusion was collected in 2019. Exclusionary fencing was built in Fall 2019, and data on plant composition and phenology was collected during 2020 on managed grazing, no grazing and uncontrolled grazing treatments. This research found strong agreement between on-the-ground measurements of plant phenological stage, phenology determined with images from near-surface digital cameras (phenocams), and Landsat satellite-based indices of plant vigor (Normalized Difference Vegetation Index). In support of Sub-objective 1D, two ARS scientists in Reno, Nevada, collaborated with a University of Nevada-Reno (UNR) bioinformatics specialist to compare cheatgrass genotypes from samples collected annually using Fstat and STRUCTURE software. This will allow us to determine whether cheatgrass genotypes vary temporally, which would imply that this invasive plant continues to adapt to its introduced range through occasional outcrossing events. This work will improve our understanding of cheatgrass invasion processes and an extension of this research will 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 delayed two years 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, stem length, as well as across-season bunchgrass density, foliar cover, and seedling survival. Preliminary analyses showed that fall and spring defoliation within seedling removal hastened senescence following defoliation, while spring defoliation decreased leaf production, stem length, and inflorescence production. Adult and seedling removal both decreased plant density and foliar cover in the first year after fire. Our results will inform managers of whether post-fire plant community structure affects restoration efficacy, and whether spring and fall defoliation treatments differ in their effects on seedling perennial bunchgrasses. Progress on Sub-objective 2B included sampling juniper berries at three western juniper sites in northern California, four juniper sites in Utah, juniper sites in central and western Nevada, and four juniper sites in central California. We dissected berries 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 at least 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. The mite that we have found to be nearly ubiquitous in western and Utah juniper populations has recently been determined through genetic analyses to be a new 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 diversity of species. This is an essential first step for potential biological control applications, and it has immediate utility for parameterizing models of juniper expansion. This work has recently resulted in acceptance of a paper on parallel evolution among arthropod communities in different juniper species in the journal Ecology. Progress on Sub-objective 2C was limited by the COVID-19 pandemic and lack of soil moisture. Collectively, desert rodent species constitute the main consumers of seeds on western rangelands, and some rodent species also provide important seed dispersal benefits to certain plants through seed caching. In such cases, rodent-made seed caches that remain in the soil are the primary source of new seedlings. The diversionary seeding concept involves broadcasting inexpensive, commercially available “diversionary” seeds as an alternate seed source to reduce the rate that rodents recover their caches and consume seeds of the plant species that is a target for restoration. This approach has been successfully applied for enhancing seedling productivity of Indian ricegrass, an important forage grass on Great Basin rangelands. A broadcast seeding experiment was initiated in October 2019 at two western Nevada study sites, and we attempted to quantify seedling emergence, but drought conditions during the following two winters resulted in no seedling establishment. Because Indian ricegrass seeds remain viable through dormancy over numerous years, this effort could still yield results. A second 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 and has not been rescheduled.
1. Conserving groundwater dependent systems on grazed rangelands. During the last three years, an ARS scientist from Reno, Nevada, has worked with a private livestock ranch, the U.S. Geological Survey (USGS), University Nevada Reno (UNR), Bureau of Land Management (BLM), and the Nevada Department of Wildlife, to develop, fund and monitor a replicated grazing experiment on public lands in support of the BLM’s outcome-based grazing program. This fully replicated experiment is providing data to determine how grazing management of both livestock and feral horses affects the resistance and resilience of groundwater dependent meadow systems in the Great Basin. These meadow systems, though small in size, provide a disproportionate amount of forage and wildlife habitat, and a critical habitat for the greater sage grouse. This effort, led by ARS and UNR, has resulted in these partners reaching a common ground, installing needed fencing, and establishing several science projects within a shared experimental design.
2. Assessing soil erosion and benefits of conservation. Soil erosion is a major a concern with 21% of rangelands in the western United States degraded and vulnerable to accelerated soil erosion. To address this, ARS scientists in Reno, Nevada, Boise, Idaho, and Tucson, Arizona, developed the Rangeland Hydrology and Erosion Model (RHEM). The RHEM has become the standard tool used by federal and state agencies for assessing soil erosion on rangelands. As part of national policy, the Natural Resources Conservation Service (NRCS) adopted RHEM and mandated its use with the release of Handbook 645 in 2021.
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