Location: Watershed Management Research2010 Annual Report
1a. Objectives (from AD-416)
The overall objective of this research project is to improve scientific understanding to transfer technology related to assessing and mitigating the impacts of ecological disturbances by invasion-weeds,fire and predation on rangeland water, vegetation and animal resources within sagebrush ecosystems of the Intermountain West. The aim is to provide sound science-base information and management tools in support of private and public land management activities. Specific research objectives inclued: 1) Develop strategic management tools and guidelines for use in fire impact assessment and rehabilitation planning of sagebrush ecosystems of the Intermountain West to aid land managers in determining the location, severity and persistence of fire impacts on post-fire runoff/erosion. 2) Improve guidelines and methods for monitoring and assessing impacts of juniper encroachment and management on plant, soil and water resources in sagebrush-steppe ecosystems to enhance efficiency and success in action agency planning and implementation of juniper-control treatments throughout the Intermountain West: 3) Develop methodology for classifying seedbed microclimate and identify microclimatic thresholds for successful germination and early establishment of seeded grass species in sagebrush-steppe ecosystems to improve success of rangeland restoration efforts across the Intermountain West: 4)Evaluate the effects of landscape-scale disturbance such as fire, invasive plants, and predation on livestock productivity and livestock use of stream systems and other critical resouces of sagebrush-steppe ecosystems throughout the Intermountain West so producers and land managers can employ adaptive management and better plan for changes in animal resources use and productivity.
1b. Approach (from AD-416)
A suite of hydrology, vegetation, remote sensing and animal behavior experiments will be conducted from point to landscape scales to improve scientific understanding and produce technology for managing impacts of ecological disturbances by fire,invasive-weed and predation within sagebrush ecosystems of the Intermountain West. This research project will deliver products to aid land managers in conducting fire impact risk assessments, inventory and assessing the impacts of juniper encroachment, planning and implementing juniper-control treatments, determining seedbed-microclimatic requirements for establishment of native and introduced rangeland-grass species appropriate plant species and optimal planting time for post-fire rangeland rehabilitation and restoration treatments, evaluating livestock behavioral response and resource use following disturbance and establish appropriate post-fire livestock grazing strategies. Outcomes of this project help to assesss and quantify environmental benefits of conservation practices and improve action agency land use planning and management activities. Resultant benefits include potential savings of millions of dollars in wildfire mitigation,improve water quality by reducing sediment delivery to streams, reduced loss of forage for livestock and wildlife from juniper and cheatgrass invaion, improved species diversity and wildlife habitat, and greater livestock productivity from rangeland systems.
3. Progress Report
Extensive data from numerous field experiments of the impact of fire and juniper encroachment on runoff and erosion were used to derive estimates and develop predictive equations for concentrated flow velocity, flow width, and hydraulic friction factors for the Rangeland Hydrology and Erosion Model (RHEM). Work was initiated to use these results to estimate and predict concentrated flow erodibility and shear stress parameters. Once completed, this work will expand the applicability of RHEM to disturbed rangeland conditions. Evaluation of Light Detection and Ranging (LiDAR) for measuring rangeland vegetation characteristics demonstrated that vegetation type and slope had significant effects on the accuracy of both the vegetation and the underlying ground topography. There are larger errors on steeper slopes and for low-lying vegetation, and these errors are of similar magnitude to the height of the low-lying vegetation. By comparison, LiDAR classification of larger vegetation, such as western Juniper, is relatively accurate. LiDAR measurements were successfully fused with hyperspectral remote sensing data to correctly classify juniper presence, and the trajectory of juniper invasion at multiple sites in southwestern Idaho. The NWRC continued monitoring a 4 year experiment in the Boise foothills to investigate prescribed fire, herbicide rate, seeding rate, and species effects on restoration of these rangelands. The general experimental design was modified this year to include a wider range of seeding rates. Results suggest large impacts of fall-applied herbicide and fire on weed composition and density during the spring establishment period. A germination-response index developed from previous field germination and establishment experiments is being used to evaluate long-term probabilities of favorable weather for plant establishment, and to evaluate potential climate change effects on native and non-native/weed establishment. Cattle distribution data sets were collected on 9 study areas for the 2009 grazing season using Clark Global Positioning System (GPS) tracking collars. These 5-min interval data sets are unique in that they represent the combination of temporally-intensive animal location sampling throughout large rangeland grazing allotments over long time periods. These data sets contain both acute, short-term effects (e.g., bunching and flight events) as well as the chronic, longer-term effects (e.g., altered foraging patterns and riparian occupation durations) of wolf presence on cattle distribution patterns. GPS-Iridium based animal tracking collars were developed and field-tested on beef cattle. This technology provides global, 24-7, two-way communication between user and deployed tracking collars allowing remote data downloading and collar configuration uploading via email. These technological advancements enable researchers to detect animal behavior patterns in real-time then opportunistically intensify sampling rates to evaluate behaviors in greater detail than previously possible.
1. HYDROLOGIC RESPONSE TO MECHANICAL SHREDDING IN A JUNIPER WOODLAND. Juniper encroachment has increased fuel densities on shrub-dominated rangelands across the Great Basin, USA resulting in increased occurrence and extent of catastrophic wildfires. This has prompted land managers to search for effective fuel control methods such as mechanical shredding which reduces juniper trees to a surface soil residue. ARS scientists at the Northwest Watershed Research Center in Boise, Idaho investigated the impacts of mechanical shredding on soil compaction, infiltration and surface runoff and erosion following shredding of Utah juniper in a sagebrush/bunchgrass plant community. Experimental results indicate that minor soil compaction can result from the use of mechanized shredders; however, the shredded tree material sufficiently mitigates these impacts while also potentially reducing runoff and erosion in areas where shredding spreads tree residue beyond the canopy of the tree. Limited adverse and some positive hydrologic responses to shredding at the small plot scale indicate that shredding is a potentially hydrologically-viable fuel control method that land managers can use.
2. COMPARING CUMULATIVE-GERMINATION RESPONSES OF CHEATGRASS AND FIVE PERENNIAL BUNCHGRASS SPECIES. Cheatgrass has invaded and now dominates millions of hectares of rangeland in the western United States by outcompeting native vegetation following fire. ARS scientists at the Northwest Watershed Center (NWRC) in Boise, Idaho studied the germination response of cheatgrass and 5 different native bunchgrasses by simulating potential germination response as if they had been planted on any day during the last 38 years. By comparing potential response over such a long time period, NWRC confirmed that an average, cheatgrass is from 2-5 times faster than other species in early germination. The modeling techniques developed in this study can also be used to identify what type of future weather conditions are necessary to successfully establish desirable native plant species even after taking measures to control cheatgrass competition. With this improved understanding of climatic requirements for establishment of different species, land managers can make better and more cost-effective decisions about species selection for revegetation and restoration in a given year.
Cline, N.L., Roundy, B.A., Pierson, F.B., Kormos, P., and Williams, C.J. 2010. Hydrologic Response to Mechanical Shredding in a Juniper Woodland. Rangeland Ecology and Management. 63:467-477.