Location: Great Basin Rangelands Research2018 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.
This project is a short-term bridging project for 2060-13610-001-00D, "Invasive Species Assessment and Control to Enhance Sustainability of Great Basin Rangelands". The project is in place during the Office of Scientific Quality Review period for the next five-year project. Please see the report for the previous project for additional information. Many of the sub-objectives in the new project plan which will begin in FY19 are direct extensions of sub-objectives in the recently expired project and this bridging project, so these essentially constitute continuing research. Continuing areas of interest include soil erosion and salt transport on rangelands, expansion of native conifer woodlands, cheatgrass population genetics, passive restoration techniques using the seed dispersal services of native animals, and fire ecology. In these cases, research activities during the period covered by this report will involve either attending to details to finish the terminated project (e.g., revising manuscripts that are in the review process, reanalyzing data if needed for revisions, etc.), preparing for the research proposed in the new project with such preliminary tasks as site selection and acquiring necessary permits, or preparing additional manuscripts that were unforeseen, but motivated from research results from the previous project. Additionally, most continuing areas of study include ongoing field research that is conducted annually, so personnel will remain occupied with this work. For example, rainfall simulation, sampling of juniper populations, and monitoring water use in managed conifer forests will continue during the period of this report. Given that this short period occurs within the busiest part of the field season, it is essential to maintain the continuity of such ongoing research projects. Sub-objective 1.1: Results revealed that many of the thousands of simple sequence repeat DNA markers (SSRs) that have been developed for bread wheat are likely to also be applicable to cheatgrass genetic studies. DNASTAR Lasergene SeqNinja software was used to identify single nucleotide polymorphisms (SNPs) throughout the cheatgrass genome. Sub-objective 1.2: Journal articles have been published demonstrating that various fruit-eating bird species (e.g., American robins, Townsend’s solitaires, cedar waxwings) consume berries of western juniper and defecate the seeds, and seed-caching small mammals (e.g, yellow pine chipmunks, California kangaroo rats, pinyon mice) are secondary dispersers of juniper seeds defecated by birds. Quantitative data from this work will be used to parameterize predictive models of western juniper expansion. Sampling of Utah juniper berries was conducted at five sites in western and central Nevada. Berries were frozen for later inspection for arthropod seed predators. Western juniper berries will be sampled during fall. Objective 2: Plots are being monitored on the Strawberry fire to assess herbicide and seeding treatment effects on plant establishment and soil properties. Two new experimental sites were established in Nevada and Utah to examine the effects of post-fire grazing on surviving perennial grasses. Plants were marked and measured and grazing treatments were applied. Objective 3.2: Final reports have been sent to the Bureau of Land Management (BLM) on post-fire treatment success and suggested sampling designs for new fires. Diversionary seeding, which uses the manipulates of the natural seed dispersal services provided by seed-caching animals was demonstrated to enhance productivity of Indian ricegrass, and new approaches deploying the diversionary seeding strategy were detailed in two journal articles. Sub-objective 4.1: Annual rainfall simulation experiments are being conducted at multiple sites to quantify erosion rates on Colorado Plateau rangelands. Sub-objective 4.2: A soil particle size analyzer was purchased to contribute to soil analysis as part of the National Wind Erosion Research Network. Coordination with BLM offices to locate a post-fire site is in progress. Activities to prepare for the new project and preliminary tasks include the annual water use monitoring in managed conifer forests conducted at the Porter Canyon Experimental Watershed in central Nevada. Initial population clustering analyses have begun for cheatgrass populations sampled throughout Nevada using single nucleotide polymorphism (SNP) markers recently developed for cheatgrass.
Dimitri, L.A., Longland, W.S., Tonkel, K.C., Rector, B.G., Kirchoff, V.S. 2018. Impacts of granivorous and frugivorous arthropods on pre-dispersal seed production of western juniper (Juniperus occidentalis). Arthropod-Plant Interactions. 12(3):465-476. https://doi.org/10.1007/s11829-018-9603-3