The soil organic carbon (SOC) pool in mineral soil horizons plays an important role in the global C cycle. Any long-term change in forest SOC and, in particular, mineral soil SOC pools is a major uncertainty in credible terrestrial C budgets. Strategies are needed to increase the mineral soil SOC pool in forests because: (i) the turnover time of SOC increases with increase in soil depth, and (ii) the mineral soil SOC is chemically and physically stabilized. We compared the total SOC and TN pools, chemically and physically separated C fractions, and C and N pools in fine roots in a pedon under deciduous forest at the North Appalachian Experimental Watershed near Coshocton, Ohio, USA. The SOC pool (Mg ha-1) was the highest in 0-20cm depth (47.4), and smaller in 20-30cm (6.9) and 30-46cm (6.7). The SOC and TN concentrations sharply decreased with depth. Fine root C and N pools (Mg ha-1) were much larger in 0-20cm depth (0.71 and 0.025) than in underlying horizons. Although only 22% of the SOC pool was stored below the A horizon, 58% of the chemically stabilized and 31% of the physically stabilized fractions of the entire SOC pool occur in the mineral soil horizons. Yet, in soils under coniferous forest mineral soil horizons contributed more to SOC stabilization than surface horizons. Thus, enhancing translocation of photosynthetically fixed CO2 into the lower horizons of soils under forests by introducing functionally important tree species (i.e., those having deep and extended root profiles with high contents of chemically recalcitrant biomacromolecules and a high root turnover) and promoting the close association of soil microorganisms and SOC with the mineral phase is a potential but overlooked strategy to stabilize the SOC pool and mitigate the human-induced climate change.