Chemically stabilized soil organic carbon fractions in a reclaimed minesoil chronosequence: implications for soil carbon sequestration

Abstract

With adoption of appropriate reclamation strategies, minesoils can sequester significant amount of soil organic carbon (SOC). The objective of this study was to isolate different SOC fractions and coal-C in a reclaimed minesoil chronosequence and assess effects of increasing time since reclamation on each SOC fraction and selected soil properties. The chronosequence was comprised of four minesoils with time since reclamation ranging between 2 and 22 years. Total SOC (TSOC, summation of all SOC fractions), ranged between 20 and 8 g kg−1, respectively, at the oldest (Mylan Park) and youngest (WVO1) minesite, indicating increasing SOC sequestration along the chronosequence. The humin fraction accounted for about 43 and 7 % of TSOC, respectively, at Mylan Park and WVO1, indicating increasing humification and biochemical stabilization of SOC with increasing time since reclamation. At WVO1, >60 % of TSOC was apportioned among the acid-hydrolysable (labile) and mineral-bound SOC fractions. Total soil carbon (TSC, TSOC + coal-C) were significantly (p < 0.05) related to the humin fraction in older minesoils, whereas with the acid-hydrolysable (labile) fraction in the younger minesoils indicating that C stabilization mechanisms differed substantially along the chronosequence. Coal-C was unrelated to any SOC fraction at all minesites indicating that SOC sequestration estimations in this chronosequence was unaffected by coal-C. Soil cation exchange capacity and electrical conductivity were significantly (p < 0.05) related to the humin fraction at Mylan Park while to the acid-hydrolysable and mineral-bound SOC fractions at WVO1 indicating that the relative influences of different SOC fractions on soil quality indicators differed substantially along the chronosequence.