Influence of fire regime on patch dynamics of sagebrush dominated landscapes in the Utah-Wyoming Rockies, Utah Highlands and Eastern Great Basin

Zach Nelson, Graduate Research Assistant, University of Nevada - Reno , Ecology, Evolution and Conservation Biology Program

Dr. Peter Weisberg, Assistant Professor of Landscape Ecology, University of Nevada - Reno, Department of Natural Resources and Environmental Science

Stanley Kitchen, Research Botanist, USFS, Rocky Mountain Research Station

Abstract: Knowledge of past fire regimes associated with mountain big sagebrush-dominated landscapes is inadequate for accurate assessment of current departures from historic conditions. Scientifically-based understanding of the role of fire in big sagebrush ecosystems is particularly critical when managing rangeland that include habitat for sagebrush dependent species such as sage grouse and Pygmy rabbits. Determining fire frequency based upon old fire-scarred trees have been widely utilized for management purposes but are untested, and may have limited application, because of the limited number of supporting studies. Most important, these studies fail to address the uncertainties associated with fire behavior across the levels of available fuel materials.

Alternative estimates of big sagebrush fire frequency have been based upon the time required for big sagebrush to recover after fire, as measured by percent cover and plant density. Similarly, maximum fire-free intervals for big sagebrush communities prone to invasion by evergreen trees are estimated based upon the time required for tree invasion and dominance. Published studies of mountain big sagebrush post-fire recovery are also limited primarily to higher latitudes, and as a rule are not linked to tree invasion studies.

This project will provide tree-based estimates of fire frequency for mountain big sagebrush from multiple sites located in the southern half of its distribution. It will generate estimates for shrub recovery and tree invasion rates for the same region. It will provide a test of the appropriateness of using previously burned trees to estimate fire frequency for mountain big sagebrush. We will also be using computer simulation models of fire and plant community response to determine the adequacy of tree scar-based estimates of fire frequency for mountain big sagebrush and provide a framework for extrapolating our results to un-sampled landscapes.

Funding provided by: Joint Fire Science AFP

Project duration: September 2007 – August 2010

Presentations:

Z. Nelson, P. Weisberg, S. Kitchen, and D. Ko. 2010. Simulation of mountain big sagebrush (Artemisia tridentata spp. vaseyana) persistence under different combinations of fire size and frequency.Wildland Shrub Symposium, Logan, Utah, oral presentation.

Z. Nelson and P. Weisberg, S. Kitchen, and D. Ko. 2008. Recovery after fire and long term persistence of mountain sagebrush communities. Annual Meeting of the International Association for Landscape Ecology. Madison, WI, poster presentation.