Location: Great Basin Rangelands Research2009 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. Replaces 5325-11220-005-00D (2/09).
3. Progress Report
The USDA team working on CEAP has developed a new process based model for assessing soil erosion rates on rangelands. The Rangeland Hydrology and Erosion Model (RHEM) is being developed based exclusively on data collected from rangeland erosion experiments, and is designed to use data that is routinely collected by range managers. RHEM will be used to calculate runoff and erosion at the hillslope scale and will replace the Revised Universal Soil Loss Equation on grazing lands. Efforts are currently underway to apply RHEM to NRCS National Resource Inventory (NRI) sampling sites as a means of producing the first national assessment of soil loss on rangelands. In cooperation with University of Nevada, we conducted a field study that quantified above- and below-ground carbon stocks in pinyon-juniper ecosystems treated with prescribed fire. Data clearly showed that prescribed burning caused immediate increases in surface soil C and N concentration, but over longer periods of time no statistically detectable change in soil C or N content occurred from burning. We also completed a study on 8 sites in northern Nevada and northeastern California in which individual and combinations of Fe, Cu, Zn, Mn, Fe, Ni, and Ag were applied to decrease enzyme activities associated with N-mineralization. We then monitored cheatgrass density and soil nutrient availability of N. At all sites, micronutrient additions have not decreased N availability or cheatgrass density relative to control plots. In another cheatgrass study, plants were collected as both green plants and mature seed at 8 different field sites. Red brome samples were also collected at 2 of these sites and one additional site. Samples are being shared with the US Forest Service’s Shrub Science Laboratory (Provo, UT) for collaborative research. DNA extractions and analyses have been completed for samples collected in 2008 and are ongoing for green plant Three study sites were identified in northern California for long-term study of the roles of seed dispersal and seedling recruitment in the ongoing expansion of western juniper woodlands. All juniper trees on 2 of these sites were cored for aging in 2008, and tree coring is currently ongoing at the third site. Collected cores have been prepared and aged in the lab. Juniper berry production was estimated for all trees at each site during the Fall of 2008. We conducted small mammal trapping and bird surveys and deployed automated wildlife cameras to identify potentially important seed dispersing animals. Small mammal and bird species that consume juniper berries and disperse seeds have been identified at one study site using motion-activated trail monitoring camera systems. We initiated a seed trap study at the new sites to begin quantifying levels of seed predation in western juniper. The rate at which juniper berries fall from trees was quantified at 2 field sites using paired seed traps placed under berry-laden trees.
1. Understanding what makes a plant invasive on rangelands. The introduction of non-native plant species can result in breeding among closely-related native species or populations that have historically occurred in different areas. ARS scientists in Albany, CA concluded that multiple introductions and subsequent gene flow provide a serious mode of the evolution of new invasive genotypes. Microsatellite markers were successful in identifying plants which cross-pollinated, an important aspect regarding the production of offspring that may be able to colonize new habitats. This process can present a serious problem for control efforts due to the novel genetic variation found in these new evolved populations. Understanding how gene flows across and within species will help scientists better understand and develop control treatments that target specific populations of cheatgrass which should increase the efficacy of the treatment and reduce treatment costs.
2. Carbon sequestration on rangelands. Increasing woodland cover in the intermountain western U.S. may increase carbon storage on rangeland; however, knowledge is limited about the distribution of carbon on these landscapes, especially below ground pools. ARS scientists in Albany, CA attempted to quantify the spatial distribution of soil carbon in expansion woodlands, and to determine prescribed fire’s effect on soil C and N in pinyon-juniper woodlands. Prescribed burning caused immediate increases in surface soil C and N concentration, but over intermediate to longer periods of time no statistically detectable change in soil C or N content occurred from burning. This research indicates that proposed fuel load reduction treatments within the pinyon-juniper woodlands of the Great Basin should have no impact on long-term carbon sequestration while also providing an effective means of improving watershed health of native rangelands and reducing the cost associated with catastrophic wildfires within the Great Basin.
5. Significant Activities that Support Special Target Populations
The Research Unit worked with University of Nevada at Reno to develop a workshop on jobs in natural resources for Piute tribe high school students. During the 1 week summer workshop the high school students were provided an overview of jobs in natural resources on the first day and a tour of ARS and University of Nevada at Reno research facilities. On each of the following days the students were hosted by a scientist who took them to the field to demonstrate different techniques to measure abiotic and biotic parameters used to define watershed health within the Truckee river basin. Most research conducted through this research project is in support of small farms and/or ranches that need economically viable methods of controlling invasive weeds and sustainably managing Great Basin rangelands. In particular we work closely with ranchers in central Nevada on control of salt cedar, cheatgrass and management issues related to pinyon-juniper woodlands. Through our outreach program and sponsorship of conferences and workshops over 500 people have been engaged with the project and have learned about our rapidly developing new technology and techniques to mange Great Basin rangelands.