Properties and Potentials of Coal Mine Soils in Southwest Virginia 29 Years After Establishment

Abstract

Current reclamation research following surface mining in the Appalachian coal region seeks to measure carbon (C) and nutrient accumulation and retention under forest vegetation to better understand the role of reforestation in the re-establishment of these ecosystem services. This study capitalized on the Controlled Overburden Placement Experiment (COPE), a 29-year-old reclamation research installation in southwestern Virginia, to estimate long-term mine soil C sequestration potentials and nutrient capitals after different reclamation strategies. The COPE includes two studies, a rock mix study (RM) comparing topsoil substitutes created from different ratios of local overburden [pure sandstone (SS), pure siltstone (SiS), 2:1 SS to SiS, 1:1 SS to SiS, and 1:2 SS to SiS], and a surface amendment study (SA) comparing organic amendments [control (CON), natural topsoil (TS), sawdust (SD), and 22 Mg ha-1 (22B), 56 Mg ha-1 (56B), 112 Mg ha-1 (112B) and 224 Mg ha-1 (224B) of biosolids] on a common 2:1 SS to SiS topsoil substitute. In the RM, overburden selection significantly affected soil nitrogen (N) and C concentrations as well as many other soil chemical [e.g., available phosphorus (P), pH, and other macro- and micronutrients) and physical (e.g., sand, silt and clay contents) properties. C sequestration rates were also significantly different and ranged from 0.13 to 0.47 Mg C ha-1 yr-1. Many of the differences demonstrated relationships with the mineral make-up of the RM treatment. The SA mine soils also differed significantly in many properties after 29 years, including N, C, and many other nutrient concentrations and contents. C sequestration rates were also significantly different with the SD and 224B treatments having negative sequestration rates, and the remaining treatments ranging from 0.23 to 0.80 Mg C ha-1 yr-1. Collectively, the results demonstrate that topsoil substitutes and surface amendments show divergent trends in soil C and nutrient dynamics after nearly three decades of development and stress the importance of post- mining reclamation based on available materials and reclamation goals.