Strengthening a state-and-transition model for wyoming big sagebrush dominated ecological sites in Eastern Nevada. Roche, Richard^*,1, Swanson, Sherman², ¹ University of Nevada, Reno - Dept. of Natural Resources and Environmental Science, Reno, Nevada, United States of America²

ABSTRACT- For decades, range condition was measured by methods that assumed all vegetation changes were equally significant and could be easily reversed. New approaches are utilizing concepts that better describe relationships within plant communities and their soil components. State-and-transition models are one concept that has received much attention in the past 15 years. It is apparent that for these models to be useful to land managers, they must be composed on regional and ecological site scales, because of site specific variations in soil, vegetation, precipitation, and disturbance potential. Forty (40) Wyoming big sagebrush (A. tridentata ssp. wyomingensis Beetle and Young) dominated ecological sites in Eastern Nevada were monitored for species presence, frequency, and cover as well as surface soil stability and sagebrush age. Data was compared among sites and to historical data collected on these permanent monitoring stations at least once in the past 3 decades. Sagebrush was aged and a regression model for age-stem diameter relationships was calculated. One goal was to capture information about these communities before and/or after the crossing of a threshold, by observing these sites in different states with methods employed by managers on the ground. Preliminary results indicate that changes in species composition and frequency have occurred throughout the three decades of monitoring. Several site characteristics, including shrub cover, sagebrush age, surface soil stability, and the frequency of perennial herbaceous species provided insight on state-and-transition models being developed in Eastern Nevada, their management keys, and how to better identify states approaching a threshold.

KEY WORDS: states, wyoming big sagebrush, thresholds, range condition