Increasing carbon (C) storage in soils of degraded lands, such as surface coal mines, is of interest because of its potential role in mitigating increases in atmospheric CO2. While it has been shown that reforesting degraded lands can significantly increase C storage in soils, there are limited studies addressing what processes control soil C in these systems. A study was initiated with the following objectives: 1) quantify the amount of soil C accumulating on reforested mine lands; and 2) examine several biological processes that govern the amount of C sequestered into soil (decomposition, soil respiration and microbial dynamics). A chronosequence approach was used to examine C changes with time in reforested mine lands (years 1, 3, and 8) and unmined regenerating clear-cuts (years 4, 12 and 20). From a C perspective, our results indicated that the young reforested mines (ages 1 and 3) differed significantly from the older mines (age 8) and all regenerating clear-cuts for all parameters examined. However, after 8 years litterfall, microbial biomass C and nitrogen (N), microbial activity, litter decomposition and CO2 efflux were similar on the mine as that found on the 12-year-old naturally regenerating clear-cut. Although soil organic C (SOC) content was lower on the reforested mines than the regenerating forests, rates of SOC accumulation were greater on the mine sites, likely because the young mine lands were initially devoid of SOC and conditions were suitable for rapid sequestration.