Vegetation diversity and heterogeneity on abandoned gas well pads in the Piceance Basin of western Colorado

Background/Question/Methods We are exploring the recovery of vegetation and soil resource patterns following oil and gas development in the Piceance Basin in western Colorado. Disturbed areas are generally characterized by a loss in heterogeneity in vegetation and soil structure and function. We identified eight abandoned well pads and two reference sites to compare soil and vegetation characteristics. All sites are located in Rio Blanco County, Colorado. The most recently abandoned site had only just had the topsoil replaced in the spring prior to sampling, while the oldest site was abandoned in 1967. At each site, we established a 9m x 12m sampling grid. We randomly located a point in each of 48 1.5m x 1.5m grid areas. We also randomly located 4 subplots of 2m x 2m, and sampled 16 random locations within each subplot. We sampled a total of 112 points in each plot. Plant species identity in the top canopy and understory was determined at each point.

Results/Conclusions Vegetation in reference locations was dominated by big sagebrush (Artemisia tridentata) and was characterized by both a diverse herbaceous understory and distinct patches of bare ground. Well pads reclaimed within the last 10 years were nearly uniformly dominated by an introduced annual grass (Bromus tectorum) or lacked vegetation. Well pads abandoned for at least 30 years were characterized by a nearly uniform shrub cover (primarily rubber rabbit brush (Ericameria nauseosa) and broom snakeweed (Gutierrezia sarothrae)), and a depauperate herbaceous community. These results indicate that even 40 years after abandonment, pre-disturbance sagebrush communities have not yet recovered. Practices that promote heterogeneity in soils and vegetation at the time of reclamation may aid in the achievement of reclamation objectives of these sites.