Sagebrush steppe recovery on 30–90‐year‐old abandoned oil and gas wells

Abstract

Oil and natural gas extraction is rapidly expanding in semiarid intermountain big sagebrush ecosystems of the western USA. Formerly covering over 60 million ha, this ecosystem has lost almost half its area due to land use changes. In this study, we measured the natural recovery of the big sagebrush plant community across a chronosequence of 29 oil and gas well sites that were abandoned without reclamation between 1923 and 1980. We measured big sagebrush cover and density with strip transects inside and outside of the well sites, and we estimated big sagebrush biomass using both canopy measurements and allometric equations. Cover of other shrubs, grasses, and forbs was estimated with line transects inside and outside of well sites. We estimated that it takes at least 87 years for Wyoming big sagebrush cover to recover naturally, although big sagebrush density recovered in fewer than 70 years. Grasses and non‐sagebrush shrubs recovered rapidly, shown by the high cover of those groups in the youngest sites. We found none of the invasive plants that are common in disturbed big sagebrush communities in other parts of the big sagebrush range. The forbs that account for the largest portion of plant species richness in semiarid ecosystems and promote consumer diversity showed very little indication of recovery after 87 years. Our results suggest that reclamation efforts in disturbed big sagebrush plant communities in southwestern Wyoming should target big sagebrush and forbs.