The Reno Great Basin
The Reno Great Basin Ecology Laboratory at the Rocky Mountain Research Station uses a collaborative, interdisciplinary approach to increase understanding of Great Basin ecosystems and to develop approaches for maintaining and restoring their integrity. The lab and its collaborators focus on the region’s major ecosystem types, Sagebrush ecosystems, Pinon and Juniper ecosystems, and Riparian ecosystems, and have study sites located across the Great Basin. Multiple temporal (early Holocene to present) and spatial scales (watershed to stream reach) are used to address research questions.
The Reno Great Basin Ecology Laboratory consists of two research ecologists:
- Jeanne Chambers, Research Ecologist. Research focus: disturbance and restoration ecology; global change processes; invasive species, especially annual grasses; and arid and semi-arid shrublands, woodlands, riparian ecosystems and alpine ecosystems.
- Robin Tausch, Scientist Emeritus. Research focus: ecology and management of vegetation changes in the Great Basin and modeling the growth and dynamics of individual plants, and of plant communities, as self-organized systems.
Ecology, Management and Restoration of Riparian Ecosystems
Many riparian ecosystems in the central Great Basin are severely degraded due to the effects of stream incision (down cutting) on stream processes and riparian ecosystems. The Great Basin Ecology Laboratory is studying (1) the underlying geomorphic, hydrologic and vegetation processes structuring these ecosystems, and (2) the causes of degradation – specifically, climate change and human-induced disturbance. We are using a basic understanding of the processes influencing these ecosystems and causes of degradation to determine the most effective methods for their management and restoration. The spatial scales addressed include the watershed, riparian corridor, and stream reach or riparian ecosystem, while the temporal scales include the mid-late Holocene (last 5,000 years), post-settlement (after 1860) and present. The research is highly interdisciplinary in nature and currently represents a cooperative effort among the USDA Forest Service, Rocky Mountain Research Station and Humboldt-Toiyabe National Forest and Environmental Protection Agencies’ Office of Research and Development. Collaborators include the University of Nevada, Reno, Western Carolina University, University of Tennessee and Lafayette College. Some projects include:
- Ecology, Management and Restoration of Great Basin Meadow Ecosystems — In the central Great Basin, meadow complexes, or areas with shallow water tables that are dominated largely by grasses and carices, are at especially high risk of degradation. They often occur in hydrologic and geomorphic settings that are susceptible to stream incision. Stream incision usually results in a drop in the base level for groundwater discharge and, consequently, deeper water tables. Because riparian vegetation depends on elevated water tables, major changes in the structure and composition of meadow ecosystems are occurring. For example, encroachment of upland shrubs and trees has resulted in a net loss of meadow vegetation. This project is examining (1) the factors affecting the sensitivity or, conversely, resistance of streams and their associated meadow complexes to stream incision, and (2) the underlying geomorphic, hydrologic and biotic processes related to meadow degradation. It is using this process-based understanding to develop management and treatment options for these important ecosystems.
- The Great Basin Ecosystem Management Project for Restoring and Maintaining Riparian Ecosystems — Initiated in 1992 to address the problem of stream and riparian ecosystem degradation within the central Great Basin, the Great Basin Ecosystem Management (EM) Project used an integrated, interdisciplinary approach to increase understanding of the effects of climate change and anthropogenic disturbance on riparian areas, and to elucidate the connections among watershed and channel processes, hydrologic regimes and riparian ecosystem dynamics. The EM Project was unique in that it addressed temporal scales ranging from the mid-Holocene to the present and spatial scales ranging from entire watersheds to localized stream reaches. The Project’s process based and multi-scale approach was used to develop guidelines and methods for maintaining and restoring sustainable riparian ecosystems. Results of the EM Project are being used to accomplish the series of interrelated objectives as shown in the hierarchical classification system chart below. Forest Service funding for the project ended in 2009. The current emphasis is on maintaining long-term monitoring of precipitation and water tables in key riparian ecosystems, data archiving and syntheses.
Hierarchical classification system
Watershed Sensitivity to Disturbance — A Process-Zone Approach — Results of our earlier investigations clearly show that most stream systems in the central Great Basin are currently unstable or have unstable reaches, and that the dominant geomorphic response during the past 1900 years has been channel incision. Although the general pattern of geomorphic response is similar among watersheds, the rate and magnitude of response differs considerably indicating that the watersheds differ in sensitivity to disturbance. Some basins have completely incised and appear to have re-established new equilibrium morphologies, whereas others are actively incising, prone to catastrophic incision over short periods (months to years), or highly dynamic and responsive to flood events. The response within the watersheds also varies and many of these systems are physically compartmentalized into discrete process zones that have unique geomorphic characteristics. Process zones (alternatively called river styles) can be defined as sections of a river or stream that are characterized by similar processes and landforms. This project is evaluating the use of a hierarchal process zone approach to further refine our understanding of watershed sensitivity to disturbance in the central Great Basin, and to capture the complexity among geomorphic, hydrologic and vegetation processes at spatial scales appropriate to management.
Managing Piñon, Juniper Woodlands and Sagebrush Ecosystems Exhibiting Tree Expansion
Big Creek 2004
Piñon and juniper trees are native species that occur naturally in woodland vegetation types, but that also are expanding into mid- to upper-elevation sagebrush vegetation types throughout much of their range. Expansion of the tree species into sagebrush types typically results in an increase in tree biomass and, thus, woody fuel loads, and a decrease in the understory species associated with the sagebrush type. Higher fuel loads increase the risk of larger and more severe fires, and higher severity fires further deplete the understory species. The net effect of tree expansion on sagebrush ecosystems often is a decrease in ecological resistance to invasive species and in ecological resilience or the capacity to recover after fire. Managers throughout the region are using fire and fire surrogate treatments in an attempt to decrease fuel loads and the risk of catastrophic fire and to increase the ecological resistance and resilience of sagebrush ecosystems. The Great Basin Ecology Lab is studying (1) the factors influencing the rate and magnitude of tree expansion; (2) the effects of tree expansion on sagebrush ecosystems; and (3) the response of sagebrush ecosystems to fire and fire surrogate treatments aimed at removing the tree species. Results are being used to develop decision support tools for managing piñon and juniper woodlands and sagebrush ecosystems exhibiting tree expansion. Some projects include:
- A Demonstration Area on Ecosystem Response to Watershed-Scale Burns in Great Basin Piñon-Juniper Woodlands — This Joint Fire Sciences Program project established a demonstration watershed for illustrating the feasibility and ecological effects of prescribed fire on piñon and juniper dominated ecosystems to managers, researchers, and the public in Underdown Canyon, Shoshone Range, central Nevada. It is a cooperative effort among the USDA Forest Service, Rocky Mountain Research Station, Humboldt-Toiyabe National Forest and Nevada Bureau of Land Management. Collaborators include University of Nevada, Reno, UC Stanford, Lafayette College and High Desert Ecology. The project is examining: (1) the recovery thresholds and successional trajectories of vegetation communities with different stand densities of pinyon and juniper; (2) the changes in fuel loads that occur with increasing stand densities; (3) the influence of prescribed fire on soil and plant nutrients and seedling establishment; (4) the effects of rehabilitation seeding with natives and introduced species on site recovery; and (5) the effects of the burns on animals shown to respond to similar disturbances, i.e., ants, birds and butterflies; and (6) the effects of prescribed burn projects on stream channels, sedimentation and water quality. Plot-scale burns were conducted in spring 2002 and watershed-scale burns in 2003 and 2004. Post-burn data were collected for most variables in years (2002, 2003, 2004, and 2006). Longer-term research is examining changes in soil nutrients and carbon:nitrogen budgets after fire. The demonstration area is still used for field tours.
- Changing Fire Regimes and Increased Fuel Loads: Effects on Sagebrush Steppe and Piñon-Juniper Ecosystems — This integrated research project addressed the spatial and temporal changes that occurred in sagebrush ecosystems and piñon and juniper woodlands after settlement of the region. Specifically, it determined the changes in plant community structure, composition, fuel loads, and fire regimes that occurred over the last 150 years due to the expansion of the tree species into sagebrush ecosystems. It also evaluated changes in fuel loads following settlement, and developed information on the fuel loading characteristics of ecosystems that are functional, at risk, or tree dominated. Twenty-one cross-mountain transects were systematically sampled on four mountain ranges, one range in each of the states of Oregon, Idaho, Nevada, and Utah, for a total of 555 plots. This research is providing both local and regional information on the rate of tree expansion and how this expansion is influencing ecosystem response to fire. It is allowing managers to identify both ecosystems that are at greatest risk of catastrophic fire, and those that are suitable for prescribed fire.
- Decision Support Tools for Conducting Fire and Fuels Management Projects in Piñon-Juniper Woodlands — In mountainous areas of the Great Basin, piñon and juniper expansion is occurring in a variety sagebrush ecological types that differ significantly in environmental characteristics and in species composition and abundance. Consequently, the effects of fire and fire surrogate treatments depend on the ecological type and differ over elevation gradients. The resilience of sagebrush ecological types or their ability to recover after disturbance can be predicted based on several key characteristic including environmental conditions, ecological amplitude of the trees, rate and magnitude of recent expansion, tree cover and biomass and interaction with environment, residual perennial understory species, especially perennial herbaceous species, and composition and abundance of invasive species. This project is developing guidelines for conducting fire and fuels treatments in sagebrush ecosystems exhibiting piñon and juniper expansion based on their ecological resilience. This three-year project in the Northern portion of the Monitor Range of central Nevada was initiated in 2010.
Hypothesized changes with repeated burning
Long-Term Vegetation Response to Chaining and Prescribed Fire in Eastern Nevada Piñon-Juniper Woodlands — In 1970-1971, this study sampled four chained sites and adjacent controls in eastern Nevada that were treated between 1958 and 1969. In 2008, the same sampling protocol was replicated to assess the long-term effects and efficacy of the treatments. In addition, five prescribed fires from the same area were sampled that were first treated and studied in 1975–1976. The sampling procedure used for the chaining was modified to ensure compatibility with previous sampling on the burns. Results provided the first long-term information on the effects of prescribed fire and mechanical approaches to rangeland restoration. Detailed information on the response of sagebrush ecosystems to mechanical and prescribed fire treatments was obtained, including tree ages, vegetation structure, community composition, and quantification of tree cover change since treatment. The differential effects of chaining versus prescribed fire were quantified, and the effects of site environments and initial stand conditions were determined. Results have helped to address a major knowledge gap regarding the ability of these treatments to address the long-term objectives of countering tree expansion and reducing fire risk.
- Sagebrush Steppe Treatment and Evaluation Project — The Sagebrush Steppe Treatment Evaluation Project (SageSTEP) is a comprehensive, integrated long-term study evaluating the ecological effects of fire and fire surrogate treatments designed to reduce fuel and to restore sagebrush (Artemisia spp.) communities of the Great Basin and surrounding areas. The overarching objective of the project is to define the conditions that facilitate recovery of sagebrush communities following treatment, and the conditions that result in ecological threshold crossings and the need for active restoration. Standard management treatments (fire, mechanical thinning, and herbicide) were implemented between 2006 and 2009 over gradients of cheatgrass (B. tectorum) invasion and piñon and juniper expansion at 21 different sites. An inter-disciplinary approach monitoring nearly 100 variables describing treatment effects on vegetation, soils, wildlife, and fuels is being used at all sites. A multi-variate approach to data analysis is being used to provide information on ecological thresholds and treatment effectiveness. Recommendations and guidelines will be developed for fuels management and the maintenance and restoration of sagebrush ecosystems. These results also will be useful landscape-level strategic planning and for understanding the implications of climate change. Additional information on this large, multi-investigator project can be found at SageSTEP.
Understanding Ecological Resistance to Annual Grass Invasion and Resilience to Disturbance
Increasing ecological resistance to cheatgrass
The invasion of non-native annual grasses, especially cheatgrass (Bromus tectorum
), into sagebrush ecosystems depleted by livestock grazing is having widespread ecological and economic effects. The highly flammable annual grasses are increasing fine fuels and causing larger and more frequent fires in sagebrush ecosystems. The Great Basin Ecology Laboratory is examining the environmental and ecological factors that make Great Basin ecosystems resistant to invasion and expansion of cheatgrass, and management approaches for both increasing ecological resistance to cheatgrass and restoring native ecosystems. Some projects include:
- Factors that Influence the Resistance of Great Basin Ecosystems to Invasion by B. Tectorum — Few mechanistic studies have focused on the environmental and ecological factors that influence ecological resistance or, conversely, susceptibility of ecosystems to invasion by B. tectorum. Research in other ecosystems indicates that several different factors affect the establishment and persistence of invasive species. These include (1) the ecological amplitude of the species or its ability to establish and persist under a given set of environmental conditions; (2) the ecological memory of the site as reflected in the site potential (precipitation and soils), species composition and ecological condition, and presence, abundance and type of invasive species; and (3) the type, severity and frequency of disturbance. In the Great Basin, invasion of B. tectorum varies across the landscape but is occurring most rapidly in mid-elevation Wyoming sagebrush types, in degraded rangelands with depleted understories and in response to fire. Research conducted by the Great Basin Ecology Lab is attempting to (1) better define the ecological amplitude of the species; (2) determine the effects of site conditions and species composition on resistance to B. tectorum; and (3) evaluate the effects of disturbance s like fire and herbaceous species removal on both community composition and B. tectorum. Collaborators include the University of Nevada, Reno and ARS.
- The Use of Repeated Burning to Restore Sagebrush Ecosystems Dominated by B. Tectorum — Restoration of B. tectorum dominated rangelands depends on controlling B. tectorum while simultaneously providing the conditions necessary for native species establishment. B. tectorum is highly responsive to variations in soil N availability, and reductions in available nitrogen significantly decrease B. tectorum establishment and growth. Native perennial grasses are generally more tolerant of low nutrient conditions. If soil nitrogen levels can be decreased sufficiently to reduce B. tectorum growth and reproduction, it may be possible to establish native perennial species. A possible mechanism for decreasing growth and reproduction of nitropholous annual grasses like B. tectorum is repeated burning. Fire causes the loss of N by volatilization from plant material and litter that burns and increases soil available ammonium by heating and denaturing soil organic N. Mobilization of ammonium which is ultimately converted to nitrate increases cheatgrass growth. Greater cheatgrass growth is accompanied by higher cheatgrass N content and greater ecosystem N loss when cheatgrass is burned. This project is testing the hypotheses that (1) repeated burning increases C:N ratios and decreases available N, and (2) decreases in available N lowers growth and reproduction of B. tectorum and increases establishment of native species. A study was initiated in 2008 to examine the effects of five years of repeated burning in B. tectorum dominated ecosystems on carbon and nitrogen budgets and establishment, growth and reproduction of B. tectorum and native species commonly used restoration. Collaborators include the Great Basin Ecology Lab, University of Nevada, Reno, ARS and the Winnemucca Field Office of the BLM.