Location: Watershed Management Research2013 Annual Report
1a. Objectives (from AD-416):
Management goals on rangelands are often based on a perception that the ecosystem is unbalanced or disturbed. Prioritization of management requires assessment of existing disturbance, the potential for mitigation and/or restoration, and expected benefits from conservation practices. Management plans in public and private sectors increasingly require quantification and estimation of ecological and fiscal costs and benefits of proposed land treatments. Predictions of land treatment effects, potential conservation benefits, and the relevance of alternative treatment options are very complicated in a landscape with extremely high variability in soil, vegetation, weather, management, and disturbance regime. The project objectives all address these general issues relating to the spatial and temporal variability in landscape-scale disturbance, evaluation of management treatments and their effectiveness in the context of this variability, and developing adaptive and mitigating strategies for negative impacts of invasive annual grasses, juniper expansion, and potential climate change. Each component of this program includes new and innovative basic research; enhancement, testing and validation of predictive models; and development of technology-transfer applications for use by land management agencies and other rangeland resource managers, cooperators and partners. 1) Develop management tools for hydrologic and erosion assessment of the impacts of fire, weed-invasions, and conservation practices on Great Basin sagebrush steppe rangelands to aid public and private land managers in formulating conservation strategies and selecting effective conservation practices. 2) Develop decision-support tools that will improve the success of rangeland restoration projects in the Great Basin by integrating weather, climate, micro-climate and forecast data into ecological site descriptions and conservation practice models to reduce the risks of climatic uncertainties. 3) Develop adaptive grazing management strategies for shrub-steppe rangelands impacted by fire, juniper and other invasive weeds to improve livestock productivity while enhancing other ecosystems services.
1b. Approach (from AD-416):
Rangeland resources across the Intermountain West have been severely impacted by range expansion of non-native and native weeds such as cheatgrass and juniper and altered natural wildfire regimes. Nonnative annual grass invasions into sagebrush steppe have established self-perpetuating increases in wildfire frequency and extent. At higher elevations, juniper encroachment into sagebrush steppe has occurred due to poorly-managed livestock grazing, fire suppression and climate change. Range expansion of these weeds and changes in the role of fire have negatively impacted upland and riparian ecosystem health, biodiversity, rates of runoff and erosion, livestock distribution and productivity, wildlife habitat and economic viability of rural communities. Land management agencies, nongovernmental organizations, private landowners and environmental groups across the West are seeking conservation strategies to mitigate and/or reverse negative effects of weed expansion. This project will develop management tools and guidelines to assist management of weed-disturbed rangelands under current and potential future climate conditions in the Great Basin. Specific products include: (1) management tools for assessing hydrologic/erosion risk and targeting of conservation practices; (2) weather and climate data processing tools and models for improving the success of rangeland restoration practices; and (3) guidelines for optimal management of livestock distribution and grazing behavior in intact and disturbed rangeland systems. Resultant benefits include potential savings of millions of dollars in wildfire mitigation, improved water quality by reducing sediment delivered to streams, reduced loss of forage for livestock and wildlife from cheatgrass and juniper invasion, improved species diversity and wildlife habitat, and greater livestock productivity from rangeland systems.
3. Progress Report:
This report documents progress for the parent Project 5362-13610-011-00D Assessment, Conservation and Management of Rangelands in Transition which started Feb 2013 and continues research from Project 5362-13610-009-00D Disturbance Assessment and Mitigation of Great Basin Rangeland. The Rangeland Hydrology and Erosion Model (RHEM) was tested against field data for disturbed rangeland conditions. Results indicate the model is capable of simulating elevated erosion rates due to fire as well as the rapid recovery of erosion rates often observed following fire. Ecological Site Descriptions (ESDs) are a primary resource for rangeland managers for planning as they describe key soil and plant community characteristics at a given field site. A framework for incorporating information on runoff and erosion potential into ESDs was developed and presented to users for feedback. The framework will allow users to parameterize the RHEM model for further ESD development or for conservation planning purposes. Rangeland restoration planning requires additional information on topographic effects on seedbed microclimate, and the impact of weather variability on seeded plant performance. Topographic effects on solar radiation and seedbed temperature and water relations that control potential establishment response of both native perennial grasses and introduced annual weeds were characterized based on field data. This information will be used to supplement ESD information to include effects of topography and weather on potential establishment success on disturbed rangelands in the western US. Existing methodology for disaggregating hourly weather data from daily weather parameters for the SHAW model was evaluated using 17 alternative disaggregation schemes for precipitation, humidity, wind, solar radiation and relative humidity. Results suggest that the existing disaggregation scheme was adequate for most parameters, but a new disaggregation scheme for precipitation improved model performance relative to hourly measured input data. This result allows use of more readily available daily meteorological data and greatly reduces the expenditure of time and effort for regional modeling applications. Analyses of cattle activity and movement path responses to prescribed fire treatments on mesic sagebrush steppe were completed and a manuscript describing the results was prepared and submitted for peer-reviewed publication (Journal of Arid Environments). Initial analyses of plant basal cover and species diversity responses to prescribed fire and livestock grazing treatments at Whiskey Hill were completed. Initial analyses indicate reformatting and recompiling of some of the data is required before additional analyses can be conducted.
1. Weather variability and adaptive restoration management. Highly variable weather in the western US makes rangeland restoration an extremely risky endeavor. Successful restoration requires a management approach that can adapt to variations in weather along the path to establishing the desired plant community. ARS researchers in Boise, Idaho, developed a procedure for quantifying how historical weather patterns affected variations in seed germination responses of common grasses and shrubs then created a conceptual model for using this information in an adaptive management framework for future rangeland restoration efforts. This methodology can be used by land managers to design more effective restoration plans for millions of hectares of rangelands in the western US that have been taken over by introduced annual weeds.
2. Fire as a restoration pathway for woodland encroachment. Extensive woodland expansion in the Great Basin has generated concern regarding ecological impacts of tree encroachment on sagebrush rangelands and strategies for restoring sagebrush steppe. Woody plant encroachment can destabilize a landscape by reducing understory vegetation and ground cover causing very damaging erosion of limited surface soil resources. ARS researchers in Boise, Idaho, investigated the use of fire to control woodland encroachment across the Great Basin. Fire is a viable restoration pathway for land managers to use for reversing the destabilizing impacts of woodland encroachment and preserve vital soil resources on sites where understory plants reestablish following fire.
Al-Hamdan, O.Z., Pierson Jr, F.B., Nearing, M.A., Williams, C.J., Stone, J.J., Kormos, P.R., Boll, J., Weltz, M.A. 2013. Risk assessment of erosion from concentrated flow on rangelands using overland flow distribution and shear stress partitioning. Transactions of the ASABE. 56(2):539-548.