Location: Great Basin Rangelands Research2011 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 condition 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 utilized 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 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 that by disking the site 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% in establishment of desirable seeded species. The combination of these two results were sufficient to decrease fuel loads and significantly reduced the risk of wildfire. 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. National average annual erosion rate on non-Federal rangeland is approximately 1.5 tons per year. Nationally 20% of non-Federal rangelands generate over 65% of the average annual soil loss. Over 29 million hectors 18% of the non-Federal rangelands might benefit from treatment to reduce soil loss to a sustainable level. The release of this new erosion tool now provides land managers a cost-effective tool for targeting conservation on the most vulnerable lands. Seed dispersal and seedling recruitment studies in western juniper populations were initiated to document pathways of recruitment of this invasive conifer. At least 6 small mammal species and 5 bird species have been found to feed on juniper berries and/or seeds. Results to date indicate that most birds consume juniper berries and defecate seeds intact and that all small mammal species (except for one) tend to avoid berries and take mainly seeds that are defecated by birds. Preliminary analysis supports hypothesis that juniper seedling recruitment occurs through “diplochory” or two sequential seed dispersal agents – in this case consumption of fruit by birds followed by harvesting and caching of bird-defecated seeds by rodents. Methods designed to reduce invasion by western juniper trees must account for this recruitment action in developing restoration plans. Great Basin Rangelands Research team documented that soil type mediates interactions between an invasive plant and its biocontrol agents. This study documented the need to explicitly consider soil type when selecting release sites for new agents – an agent that is minimally effective in one area may be more effective in another based on soil-plant interactions. A recently approved agent has been generally considered a disappointment as a biocontrol agent but this work shows that in areas where starthistle has invaded serpentine soils it is expected to be effective. This is especially important as serpentine soils are generally areas of critical concern as they host numerous endangered species and use of this biocontrol agent to reduce starthistle will have great conservation impact and help to recover these impacted sites in a cost-effective manner.
1. Reducing the cost in restoring Great Basin Rangelands. Over 2 billion dollars have 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. The scientific team has documented that by disking the site 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, significantly reduced the risk of wildfire, increase forage availability for wildlife and domestic livestock, and reduced the cost of revegetating a site by approximately 50%.
2. New technique predicts impact of invasive weed control saving time and money. Weed control costs time and money. A new tool was developed that allows land manager to predict the impact of a biocontrol agent on weed density, spread rate and population growth rate. This tool allows land managers to predict how a biocontrol agent will impact an invasive plant over temporal and spatial scales that are not otherwise possible. It can show land managers that an agent may be capable of reducing one measure of invader success (e.g., density), while having no impact on others (e.g., the rate at which it is spreading into uninvaded areas or its persistence over the long-term). With this new information, land managers can assess if current invasive weed control strategies will work or will they need to augment their control strategies with additional weed control practices. Adoption of this new approach in predicting invasive species control should improve efficacy of control techniques and reduce cost by minimizing number of ineffective practices deployed.
3. Tools to target conservation saving 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 a new soil prediction tool for rangelands. This tool allows land managers to predict long-term soil loss and soil loss from individual storms. This new tool provides a method for land managers to predict where erosion will occur and evaluate alternative conservation practices to assess possible benefits before soil degradation occurs. This tool has been adopted by the Natural Resources Conservation Service and is being used to evaluate existing conservation programs and how they can be enhanced and improved deliver of conservation in a more cost-effective manner by targeting areas of concern.
Rau, B.M., Johnson, D.W., Blank, R.R., Lucchesi, A., Caldwell, T.G., Schupp, E.W. 2011. Transition from sagebrush steppe to annual grass (Bromus tectorum): influence on belowground carbon and nitrogen. Rangeland Ecology and Management. 64:139-147.