Stabilization of organic carbon in chemically separated pools in reclaimed coal mine soils in Ohio

Surface mining for coal drastically alters soil properties, destabilizes soil organic carbon (SOC) and depletes SOC pools. Reclamation aims to establish a vegetation cover and replenishment of the SOC pool. Therefore, the objective of this research was to compare the SOC pool, and chemically separated C fractions in 0- to 15-cm and 15- to 30-cm depths at four reclaimed sites in southeastern Ohio: (i) Dyes Fork under forest reclaimed in 1956, (ii) Mount Carmel under forest reclaimed in 1973, (iii) Singer under pasture reclaimed in 1962, and (iv) Active Site under pasture reclaimed in 2003. The SOC pool (Mg ha− 1) from 0- to 30-cm depth was the highest at Singer (116.2), and progressively smaller at Dyes Fork (52.7), Mount Carmel (31.6) and very low at the Active Site (6.1). Only at Mount Carmel, the SOC concentrations and pool sharply decreased with increase in depth, as is the case in un-disturbed soil profiles. The amount of C preferentially bound to soil minerals in 0- to 30-cm depth was the largest at Singer (29.6 Mg ha− 1) and the least at the Active Site (1.9 Mg ha− 1), as was indicated by treatment with HF to release mineral-bound SOC. The reclaimed soil at the Singer site stored the largest pool (32.2 Mg ha− 1), and those at the Mount Carmel and Active Sites the smallest pool (3.2 and 2.9 Mg ha− 1, respectively) of non-oxidisable C, as was indicated by treatment with disodium peroxodisulfate (Na2S2O8). By comparing the oldest (Dyes Fork or Singer) with the newly reclaimed sites (Mount Carmel or Active Site) under same land use, the high potential of reclaimed sites for SOC sequestration was obvious. In particular, pasture may have a high potential for C sequestration in 0- to 30-cm depth. However, specific recommendations of land uses for SOC sequestration in reclaimed sites can be made only after chronosequence studies are done on the entire rooted soil profile including correction for any coal C impurities.