Hard Rock Mine Restoration in the Arid Southwest

Abstract

The hard rock mining industry has left a legacy of degraded landscapes and waste disposal sites in need of reclamation. Revegetation of mining affected lands is a common method for mine reclamation that has demonstrated success across a variety of landscapes. This approach involves the establishment of diverse plant communities on mine wastes. Mine wastes are generally considered poor habitats for plant growth largely due to denuded and potentially toxic soil conditions. Further difficulties with plant establishment are found in arid lands due to scant, infrequent rainfall, and extreme temperatures. My dissertation explores different methods to enhance the success of revegetation efforts on copper mines in Southern Arizona. In Chapter 1, I explore how incorporating ecological theory in revegetation planning, namely facilitation, can help improve revegetation success. I assessed the plant communities and soil chemical properties underneath the canopies of a targeted nurse plant, desert broom (Baccharis sarothroides), and compared them to exposed conditions. Chapter 2 explored how different seed application techniques, mycorrhizal inoculation, and seeding season affect revegetation success. Chapter 3 analyzed the causes of revegetation failure on a tailings pile. The native shrub, brittlebush (Encelia farinosa), initially dominated the site after seeding in 2011. Over time, there was a gradual decline in the health of the brittlebush on site, and by 2023 nearly all individuals died with no other shrub species colonizing the site. We analyzed the belowground soil conditions to understand the causes of shrub die-off. Taken in conjunction, these chapters provide a thorough exploration of methods to improve revegetation success on hard rock mines.