Soil Carbon Recovery in Reclaimed Mine Lands in the United States.

Reclaimed mine soils have great potential to accumulate and store carbon (C) in both the eastern and western United States.  Carbon has been reported to accumulate in mine soils at between 0.13 and 3.1 Mg C ha^-1 yr^-1 under re-established grasses; however, no distinction is made for various climatic regimes or the permanency of accumulated C.  Reclaimed surface coal mine soils (0-5 cm) under grassland vegetation in Virginia and Wyoming were sampled.  In Virginia, reclaimed soils typically develop from crushed rock and are completely depleted of organic C.  After 27 yrs, surface soils contained approximately 9.0 Mg C ha^-1.  Carbon accumulated at a rate of 0.34 Mg C ha^-1 yr^-1 (0.22 Mg C ha^-1 yr^-1 in protected pools).  In Wyoming, C in topsoil materials is greatly reduced (50-70%) with topsoil salvage and replacement.  Fine textured soils contained 22.9 Mg C ha^-1 after 26 yrs and coarse textured soils held 5.81 Mg C ha^-1 after 16 yrs.  Reclaimed fine textured soils accumulated 0.71 Mg C ha^-1 yr^-1 (0.16 Mg C ha^-1 yr^-1 in protected pools) while coarse textured soils accumulated 0.17 Mg C ha^-1 yr^-1 (0.03 Mg C ha^-1 yr^-1 in protected pools).  The active pool contained 35% of total C in eastern soils and 60-70% of total C in western reclaimed soils.  We can assume physical protection by soil aggregates and chemical binding of C to fine soil particles are important mechanisms for C accumulation in eastern US reclaimed soils.  In contrast, climatic conditions (i.e. low soil moisture and the subsequent effects on microbial dynamics) and soil texture contribute to C accumulation in western US reclaimed soils.