ONGOING EVALUATION OF EFFECTS FROM VARIABLE TOPSOIL DEPTHS AT A COAL MINE IN NORTHEASTERN WYOMING

摘要

After passage of the Surface Coal Mine Reclamation Act in 1977, studies on mine reclaimed areas in the late 1970's and early 1980's evaluated varying topsoil depths over unsuitable backfill on vegetation productivity and cover. In recent years, several of those earlier studies have been revisited to provide long-term results on vegetation productivity, cover and diversity. A more recent study developed in 1999 was conducted to evaluate variable topsoil depth on soil and vegetation factors at the North Antelope/Rochelle Mine (NARM). Backfill at this location did not exhibit unsuitable plant growth parameters, based on Wyoming Department of Environmental Quality (WDEQ) guidelines. The formal study evaluated vegetation parameters such as cover, production and diversity, and soil differences in pH, electrical conductivity (EC), and sodium adsorption ratio (SAR) between three treatment depths, i.e., 15, 30 and 56 cm. Reclaimed and two native vegetation reference areas were sampled three times during the 2000-2002 growing seasons. At the end of the 2002 monitoring, results were mixed. After that time, the reclaimed area only continued to be part of the ongoing vegetation monitoring program at NARM. Five years of continuous monitoring (2000-2004) were statistically analyzed to determine significant trends between topsoil depth treatments, as the seeded areas matured. No significant differences were found between treatments for two measures of cover and three measures of species richness. Although no significant differences were found between treatments for shrub density, positive increasing trends in the more shallow treatments are evident.