Shrub Densities on Pre-1985 Reclaimed Mine Lands in Wyoming

摘要

The reestablishment of native shrubs is part of the mandate under which mining companies extract mineral resources in Wyoming and other western states. Post-mining shrub density and species mixtures have been topics debated by various mine reclamation stake holders. By law, coal-mined lands in Wyoming must now meet a post-mining shrub density of 1 shrub/m2 on 20% of the affected area. To better understand the long-term results of shrub reclamation methods, we measured shrub density by species in 14 pre-1985 seedings at eight mines in three geographic regions of Wyoming. The sites studied were selected as Atriplex canescens (Pursh) Nutt. (fourwing saltbush) and grass or as Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush), fourwing saltbush, and grass post-mining communities. Shrub density and composition varied by site but typically reflected the seed mixtures used. Seedings that used a diversity of shrub species generally had greater 1994 shrub densities. Seeding rates between 60 and 1000 shrub seeds/m2 had a positive, linear relationship with shrub density up to 0.6 shrubs/m2 when sagebrush was part of the shrub seed mixture. We conclude that the likelihood of meeting the shrub standard can be enhanced by seeding diverse shrub mixtures at high seeding rates.