Investigation of sagebrush reclamation success on bentonite mined areas in the in the Big Horn Basin (Wyoming, USA)

The Big Horn Basin located in north central Wyoming has some of the largest deposits of high quality bentonite in the world. Historically, reclamation efforts to establish plant communities similar to conditions found in big sagebrush (Artemisia tridentata) grassland plant communities before mining have been limited due to the absence of shrub regulatory standards and poor response of sagebrush to reclamation efforts on bentonite mine lands. The lack of suitable shrub cover is believed to have a negative effect on sagebrush obligate species, such as the greater sage-grouse (Centrocercus urophasianus). The objective of this study was to determine if sagebrush communities were reestablishing on reclaimed bentonite mined lands in the Big Horn Basin under conventional reclamation techniques. Findings indicate that sagebrush establishment on reclaimed bentonite lands in the Big Horn Basin has not been successful using conventional methods. At study sites, sagebrush plants were not established in adequate densities on sites seeded within the past 15 years. However, it does appear conventionally reclaimed sites older than 15 years are undergoing natural recolonization of sagebrush to greater densities than found on the younger sites. In this study, 11 reclaimed and six native reference sites were analyzed throughout the Big Horn Basin. Five sites were reclaimed in the past 15 years, while six were reclaimed more than 15 years ago. The younger sites had a mean sagebrush density of 900 stems ha-1 while the older sites had a mean of 5140 stems ha -1. Native reference sites had a mean sagebrush density of 10,763 stems ha-1. Even the densities of the older reclaimed sites were only about half of observed sagebrush densities on native reference sites. These results indicate that conventional methods of sagebrush reestablishment used in bentonite mineland reclamation are ineffective in the short term, 15 years or less. That is, initial seeding efforts during site reclamation result in very little sagebrush establishment. However, over longer time periods (ca. 15-30 years), natural seed dispersal of native sagebrush from undisturbed areas surrounding reclaimed mine sites appears to have resulted in greater densities of sagebrush plants. Included are sagebrush height and canopy cover to aid in better understanding natural reestablishment rates. It is also believed that other newly developed reclamation technologies may be more effective in reestablishing sagebrush communities on reclaimed bentonite mined land.