Form Submission: Participation Entry

The probability of extreme weather events is increasing, with the potential for large-scale impacts to plants. Extreme weather conditions can result in widespread plant mortality when they exceed a species’ physiological limitations, and drought-induced plant mortality has become more frequent globally over the past two decades. In 2014, a large-scale die-off of the widespread shrub, big sagebrush (Artemisia tridentata Nutt.), was reported in southwest Wyoming, following extreme drought conditions in 2012 and subsequent extreme precipitation in September of 2013. Across 11 U.S. states, big sagebrush ecosystems provide critical wildlife habitat and support local livelihoods. The big sagebrush die-off exhibited distinct patterns across the landscape, with widespread mortality in some areas and mortality restricted to lowland positions in others, suggesting soil and landscape position contributed to the die-off. I established 51 pairs of upland and lowland plots to capture these patterns, including live upland/live lowland, dead upland/dead lowland, and live upland/dead lowland pairs. I measured the cover and number of live and dead big sagebrush plants and collected soil samples. I used soil and site information with gridded historical weather data as inputs for simulating soil water conditions from 1980 to 2016 using SOILWAT2, an ecosystem water balance model. Sagebrush mortality was greatest on sites with fine-textured soils and sites with low mean annual precipitation. Output from SOILWAT2 indicated that big sagebrush mortality was lowest at sites where 2012 drought and 2013 wet conditions were the most extreme over the simulation period. This suggests that the die-off occurred in locations that were driest on average and that big sagebrush at sites that have experienced frequent drought conditions over the past 37 years were most vulnerable to the extreme events of 2012 and 2013.