TEMPORAL CHANGES IN SOIL ORGANIC CARBON CONCENTRATION AND STOCKS IN RECLAIMED MINESOILS OF SOUTHEASTERN OHIO.

Drastic disturbances during surface mining severely depletes the soil organic C (SOC), and reclamation or restoration of degraded land can lead to the increases in SOC concentration. This research project is aimed at assessing the SOC sequestration potential of reclaimed minesoils (RMS), which are characterized by distinct age chronosequences of RMS and located in Guernsey, Morgan, Noble, and Muskingum Counties of Ohio. Three cores and three bulk soil samples were collected from each of the experimental site and one unmined site (UMS) from 0 to 15 cm and 15 to 30 cm depths in October-November 2003. Soil bulk density was the highest for the site reclaimed in 2003 (R03) (i.e., 1 year old from date of sampling) for both depths (1.24 for 0 to 15 and 1.61 Mg m^-3 for 15 to 30 cm depths). However, it did not vary among sites reclaimed in 1987 (R87), 1978 (R78) and UMS for either depth. For sites reclaimed without topsoil application, soil bulk density was significantly higher in site reclaimed in 1957 under grass (R57; 1.6 Mg m^-3) than reclaimed during the same year but under forest (R57-F; 1.2 Mg m^-3) for 15 to 30 cm depth only. No significant differences were observed in saturated hydraulic conductivity, volumes of transmission and storage pores and available water capacity of soil for 0 to 15 cm depth among sites reclaimed with or without topsoil application. Soil organic C and total N stocks were lower in R03 (3.5 Mg ha^-1 and 0.6 Mg ha^-1; respectively) than R78 (17.5 Mg ha^-1 and 1.6 Mg ha^-1) and UMS (18.7 Mg ha^-1 and 1.8 Mg ha^-1) for 0 to 15 cm depth. Soil organic C and total N stocks were also lower in R03 (3.1 Mg ha^-1 and 0.8 Mg ha^-1; respectively) than R87 (19.1 Mg ha^-1 and 1.1 Mg ha^-1) and R78 (9.2 Mg ha^-1 and 1.1 Mg ha^-1) for 15 to 30 cm depth. No significant differences were observed in SOC and total N (P (less than) 0.05) among sites reclaimed without topsoil application. Overall, coal C concentrations ranged from 0.5% (R03) to 68.4% (R69) of total soil C in 0 to 15 cm and 0.8% (R03) to 77.0% (R69) in 15 to 30 cm depth. Ignoring the stochastic effects of reclamation methods and assuming SOC stock of R03 as baseline, SOC stocks increased at a rate of 0.53 Mg ha^-1 yr^-1 for 0 to 15 cm depth and 0.31 Mg ha^-1 yr^-1 for 15 to 30 cm depth. However, the rate of increase in SOC stocks for 0 to 15 cm depth was greater in soils reclaimed with topsoil application (0.45 Mg ha^-1 yr^-1) than without (0.25 Mg ha^-1 yr^-1). These results show that reclamation with topsoil application increases the rate of SOC storage in soil and enhances the rate of soil quality improvement.