Assessment of Labile and Recalcitrant Carbon Fractions in Bulk Soils of a Secondary Forest.

Forest soils offer an enormous opportunity for carbon (C) storage and are considered one of the major terrestrial carbon (C) sinks. The potential of C sequestration in forest soils are greater on the long-term compared with agricultural soils and other related land uses. Forest soils tend to protect more stable forms of C because they are frequently left undisturbed. Assessment and monitoring of the amount and distribution of soil carbon fractions are critical to understanding C storage in soils. However, little is known of the potential for C storage in the Busby forest soils in this study. Samples were collected from surface soils under oak (Quercus spp.) and hickory (Carya spp.) trees on a Gatewood-Moko Silty-loam (Oxyaquic Hapludalfs) soil. The principal objectives of this study were to quantify the concentrations and distribution of labile (water-soluble extractable C; hydrolysable C) and recalcitrant (non-hydrolyzable –NHC) soil carbon fractions in bulk soils of this secondary forest and to establish baseline concentrations for total soil C. Sequential extraction with water of varying strengths and acid hydrolysis using 6 N HCl were used to measure the labile and recalcitrant C fractions. Whole soil total C concentrations in these soils ranged from 22.1 - 83.4 g C kg^-1 soil, with nitrogen concentration of 0.8 - 4.4 g N kg^-1 soil, in the surface soil. The contribution and implication of these C fractions to emissions of greenhouse gases in a secondary forest having only one canopy layer are discussed.