Location: Great Basin Rangelands Research2012 Annual Report
1a. Objectives (from AD-416):
The Integrated Invasive Species Control, Revegetation, and Assessment of Great Basin Rangelands project has two objectives: 1) Identify and characterize biotic and abiotic conditions and processes that affect plant community factors and ecosystem dynamics on healthy and degraded rangelands to improve the ability to predict how rangelands will respond to changing environmental conditions and alternative management practices and 2) Devise management guidelines, technologies, and practices for conserving and restoring Great Basin rangelands.
1b. Approach (from AD-416):
The research project is organized into four complementary components: (1) ecology and control of invasive plants, (2) revegetation of degraded rangelands, (3) maintaining and/or enhancing healthy rangelands, and (4) quantifying economic and environmental impacts of management practices at the landscape scale. Experiments will be conducted to understand the seed and seedbed ecology of several native and non-native grasses and shrubs. Herbicides and tillage will be used to vary content of competing vegetation as it affects shrub establishment. Research will be conducted to document ecological processes which control expansion of Western Juniper. Levels of genetic variation of selected plants will be compared between high and low quality ecological conditions sites to determine effects of disturbance on genetic diversity. Rainfall simulators will be used to characterize runoff and soil erosion processes at the scale of a plant community under different manipulative treatments (altered grazing practices, burning, and brush removal) to quantify the hydrologic impact of the conservation practices. The SWAT model will be utilize to evaluate which alternative management scenarios (i.e., a change in vegetation state as represented by changes in canopy and ground cover or vegetation composition by life form) are the most cost effective in achieving the desired environmental benefit.
3. Progress Report:
Great Basin Rangelands Research team in Reno, Nevada, has developed techniques to increase the variety and density of desirable native and introduced species when revegetating degraded Great Basin rangelands to suppress cheatgrass and decrease wildfire frequencies. The research team documented this by seeding into areas where cheatgrass had died-off from natural causes and were able to successfully establish 3.9 perennial grasses/ft² compared to 0.6/ft² outside of the die-off zone. Our previous plant materials testing narrowed the species list to 4 wheatgrasses and these species went to seed in their first growing season despite record drought conditions. In an associated study the team found that by disking sites that were still dominated by cheatgrass prior to seeding the resulting action buried the majority of cheatgrass seeds and prevented the cheatgrass seeds from germinating. This resulted in an 83% decrease in cheatgrass densities and a corresponding increase of 244% establishment of desirable seeded species. The combination of these two results was sufficient to decrease fuel loads and significantly reduced the risk of wildfire and provides a variety of treatments depending on site conditions for reducing the impact of cheatgrass on Great Basin Rangelands. We continued ongoing population genetic research with the annual weeds cheatgrass and medusahead using SSR (i.e., microsatellite) markers to characterize populations and identify vulnerabilities that can be exploited when developing treatments to reduce the impact of cheatgrass. Research on animal seed-dispersal vectors of expanding populations of western juniper continued this year, with successful results from a field experiment comparing germination rates of seeds dispersed by birds, by small mammals, and by neither of these seed dispersers. Results clearly indicated that a two-phase dispersal system yields the best seedling recruitment in which birds consume fruits, defecate the seeds, and small mammals then harvest and cache the seeds from the bird droppings. Results of a successful field experiment using “diversionary seeds” to enhance seedling recruitment of Indian ricegrass from seeds cached by small mammals were published in a peer-reviewed article in the journal Restoration Ecology. This was in collaboration with a USGS scientist. The Rangeland Hydrology and Erosion Model tool was used to estimate runoff and erosion at the hillslope scale for over 10,000 sample points in the 17 western states on non-Federal rangelands. Modeling of soil erosion based on quantitative data derived from the rangeland National Resources Inventory (NRI) can be used to predict the effectiveness of alternative management actions and support cost-benefit analysis to optimize return on investment in conservation. The spatially unbiased nature of the rangeland NRI assessment allows for rapid determination of regional needs and identification of where conservation may be most cost-effective in arresting land degradation and enhancing ecosystem services. This same concept can be utilized to inform policy and provide a quantitative mechanism to justify when targeting to meet specific goals.
1. New technology is available to reduce the cost of restoring Great Basin Rangelands. Over 2 billion dollars has been spent fighting wildfires in the western United States and millions more in trying to restore these devastated landscapes over the last decade. Scientists in the Great Basin Rangelands Research Unit in Reno, Nevada, have been working on methods to cost-effectively revegetate these landscapes and reduce the frequency of burning. Our herbicide research on cheatgrass control yielded a 95.8% decrease using Plateau and 98.7% decrease using Landmark which resulted in 4.8 perennial grasses/ft² in the Plateau plots and 6.6 perennial grasses/ft² in the Landmark plots despite only receiving 6.3” of precipitation. No perennial grasses established in the control plots and the cheatgrass density and the associated fuel load is a serious problem. Our Cheatgrass Control Methods resulted in a cost-effective technique to establish a dense long-lived perennial grass population capable of suppressing cheatgrass, decreasing cheatgrass fuel loads, and subsequent associated wildland fires.
2. Targeting conservation saves money and land. Soil erosion of agricultural lands and sedimentation of the rivers and lakes is one of the largest and persistent environmental problems facing the world. It is estimated that soil loss costs the Unites States over $6 billion dollars every year. Scientists in the Great Basin Rangelands Research Unit in Reno, Nevada, in collaboration with ARS scientists in Boise, Idaho, and Tucson, Arizona, have developed the Rangeland Hydrology and Erosion Model (RHEM). The RHEM model was used to develop the first national quantitative assessment of soil erosion on western rangelands using data from the NRCS National Resources Inventory program. Results from this assessment were highlighted in the USDA Resource Conservation Act and National Conservation Program publications that were delivered to Congress in support of the 2012 Farm Bill and document how targeting conservation can save money and land.
3. Rodents can be utilized to restore Great Basin environments. Seed harvesting, consumption, and dispersal through caching by granivorous (i.e., seed-eating) desert rodents have profound impacts on specific plant species and on species composition of arid plant communities. The feasibility of utilizing the seed dispersal services of native animals as a passive restoration strategy was successfully tested at a field scale for the first time by broadcasting millet as a “diversionary seed” over 1-ha plots in areas where heteromyid rodents typically cache Indian ricegrass seeds in abundance. Under these circumstances, rodents cached and preferentially recovered the preferred diversionary seeds before beginning to consume the less desirable target seeds. Consequently, more target seeds were available for emergence as seedlings using this passive restoration scheme. We documented this enhanced seedling recruitment in a recently published article in Restoration Ecology.
4. Cheatgrass density does impact establishment of native species used to restore degraded Great Basin rangelands. Surprisingly little is known about how climate change coupled with cheatgrass invasion will affect the long-term persistence of sagebrush populations. ARS researchers in Reno, Nevada, continue to measure population-level performance of sagebrush when grown in competition with low and high densities of cheatgrass under different climate change scenarios across an elevation gradient. The research indicates that lower elevation populations of sagebrush will decline in the face of climate change and cheatgrass invasion. Higher elevation populations and sites with higher annual precipitation, have greater resilience and resistance to invasion by cheatgrass and are likely to persist and continue to provide critical ecosystem services.
5. Introduced plants can provide valuable ecosystem services. ARS scientists in Reno, Nevada, and Logan, Utah, have been investigating the risks and benefits of the introduced plant ‘Immigrant’ forage kochia (Bassia prostrata, formerly Kochia prostrata). This perennial semi-evergreen half shrub averages 1 to 3 feet in height and can grow in habitats that receive 5 to 27 inches of annual precipitations, and survives the extreme temperatures (-25 to 104ºF) found in arid deserts. ARS scientists have determined that forage kochia is excellent winter forage, especially for livestock and wintering mule deer herds; is competitive with cheatgrass; can slow the spread of wildfires; and is widely adapted to soils found across semi-arid cold deserts of the western United States. Research conducted over the last 25+ years by the USDA-ARS scientists at Logan, Utah, and Reno, Nevada, have documented that forage kochia has shown no evidence that it is invasive and will spread outside of original planting area into established plant communities. Forage kochia has proven to be a valuable tool in revegetating disturbed rangelands destroyed by cheatgrass invasion and repeated wildfires and prevents soil erosion.
6. Starving cheatgrass of essential nutrients may prevent invasions and lead to opportunities for successful restoration of Great Basin rangelands. Cheatgrass is an exotic annual grass causing ecosystem degradation across the entire western United States. ARS scientists in Reno, Nevada, have investigated potential mechanisms by which the perennial grass, crested wheatgrass, can be used to suppress cheatgrass. Research focused on understanding the role of nitrogen in the susceptibility of the site to invasion to cheatgrass. Scientists found that crested wheatgrass does not suppress cheatgrass by controlling extractable Nitrogen (N) below a threshold level. Rather, scientists hypothesize that it may limit the conversion of ammonium-N to nitrate-N and thereby reduce nitrate-N availability to cheatgrass and its ability to invade and dominate a site.Finzel, J.A., Seyfried, M.S., Weltz, M.A., Kiniry, J.R., Johnson, M.V.V., Launchbaugh, K.L. 2012. Indirect measurement of leaf area index in sagebrush-steppe rangelands. Rangeland Ecology and Management. 65:208-212.