Skip to main content
U.S. flag

An official website of the United States government

Estimating abiotic thresholds for sagebrush condition class in the western United States

March 1, 2020

Sagebrush ecosystems of the western United States can transition from extended periods of relatively stable conditions to rapid ecological change if acute disturbances occur. Areas dominated by native sagebrush can transition from species-rich native systems to altered states where non-native annual grasses dominate, if resistance to annual grasses is low. The non-native annual grasses provide relatively little value to wildlife, livestock, and humans and function as fuel that increases fire frequency. The more land area covered by annual grasses, the higher the potential for fire, thus reducing the potential for native vegetation to reestablish, even when applying restoration treatments. Mapping areas of stability and areas of change using machine-learning algorithms allows both the identification of dominant abiotic variables that drive ecosystem dynamics and the variables’ important thresholds. We develop a decision-tree model with rulesets that estimate three classes of sagebrush condition (i.e., sagebrush recovery, tipping point [ecosystem degradation], and stable). We find rulesets that primarily drive development of the sagebrush recovery class indicate areas of midelevations (1 602 m), warm 30-yr July temperature maximums (tmax) (30.62°C), and 30-yr March precipitation (ppt) averages equal to 26.26 mm, about 10% of the 30-yr annual ppt values. Tipping point and stable classes occur at elevations that are lower (1 505 m) and higher (1 939 m), respectively, more mesic during March and annually, and experience lower 30-yr July tmax averages. These defined variable averages can be used to understand current dynamics of sagebrush condition and to predict where future transitions may occur under novel conditions.

Publication Year 2020
Title Estimating abiotic thresholds for sagebrush condition class in the western United States
DOI 10.1016/j.rama.2019.10.010
Authors Stephen P. Boyte, Bruce K. Wylie, Yingxin Gu, Donald J. Major
Publication Type Article
Publication Subtype Journal Article
Series Title Rangeland Ecology & Management
Index ID 70211902
Record Source USGS Publications Warehouse
USGS Organization Earth Resources Observation and Science (EROS) Center