English

Abstract

Particulate organic matter (POM) and aggregate recovery following mining disturbances are important for soil biogeochemical properties and ecosystem function. The objective of this study was to track POM accumulation and aggregation in reclaimed soils following coal mining in southwestern Virginia. A chronosequence of sites was selected based on shifts in vegetation communities with succession, typically occurring between 0-2, 5-7, 16-20, and 38-42 years since reclamation. Undisturbed adjacent forested sites were also sampled. The 0-2 yr old sites were covered with grasses and forbs, the 5-7 yr sites by thick stands of Lespedeza cuneata, the 16-20 yr sites predominately with Festuca arundinaceae and patches of deciduous trees (Acer rubrum, Oydendrum arborea, etc.) and the 38-42 yr old sites with a mix of Pinus taeda and deciduous forest with a grass understory. Undisturbed sites predominantly supported mixed Appalachian deciduous forest. Available POM (inter-aggregate) and physically protected (intra-aggregate) forms were determined using a density flotation technique and aggregate size distribution with wet sieving. Inter-aggregate POM did not change across site ages; however, intra-aggregate POM increased significantly between the 5-7 and 16-20 yr old sites and remained unchanged through the 38-42 yr old reclaimed site. Inter-aggregate POM reached levels similar to undisturbed sites, while intra-aggregate POM weights were almost threefold that of undisturbed sites after 16-20 years. By observing just the available POM, we would conclude that reclaimed systems recover to an protected POM, reclaimed system POM storage greatly exceeded undisturbed soil conditions. A positive relationship was observed between small macroaggregates (250-2000 μm) and intra-aggregate POM, suggesting that protection of POM by small macroaggregates in reclaimed systems is extremely important for POM accumulation and subsequently ecosystem function within a period of 20 years. We can also argue the greatest rates of POM accumulation and aggregate formation occur under early succession communities with grasses and forbs rather than under late succession forested communities.