| The potential of soil organic carbon (SOC) sequestration varies between ecosystems and is probably the highest through reclamation of degraded lands. Therefore, lands subjected to mining and eventually reclaimed are appropriate areas to study the potential of degraded lands to sequester SOC. A chronosequence (0--50 years) of reclaimed mine soils, were studied to determine the potential and assess mechanisms of SOC sequestration. The ameliorative effect of reclamation was conspicuous because of temporal gains in SOC pool, decrease in compaction, and improved soil structure. The SOC pool of the 20--25 year old reclaimed sites surpassed that of the control sites, which were 65--70 year old reclaimed sites. There was strong correlation between temporal changes in minesoil aggregation and SOC accumulation. During the initial stages of reclamation, the SOC content associated with the microaggregate fraction (<0.25 mm) was highest (stability of SOC pool), but by the end of reclamation period, the SOC content of the macroaggregate fraction (>0.25 mm) was the highest (positive impact of reclamation). However, the % SOC of the total in the macroaggregate fraction in old reclaimed sites was not as high as that in the control sites suggesting incomplete C sequestration. There were no distinct trends in clay, silt and sand contents over the reclamation duration but the SOC content in these fractions increased over the reclamation duration. The clay size fraction contained the highest SOC content. However, the SOC content of the silt and sand size fraction was substantial, showing that the SOC pool was still unstable. Humification of soil organic matter (SOM) increased over the duration of reclamation for all treatments, but was lower than that of the control sites. The study showed that the potential of reclaimed minesoil to sequester C was high at 2--3 Mg ha--1yr--1, highest being in pasture treatment with topsoil application. In addition, it could take 100--150 years for SOC pool in reclaimed minesoils to achieve equilibrium. |
