Post-reclamation Age Effects on Soil Physical Properties and Microbial Activity Under Forest and Pasture Ecosystems

During surface mining and subsequent reclamation efforts, physical, chemical, and biological properties of soils are disturbed. A study was conducted to evaluate the effects of age chronosequence on soil physical property and microbial activity in chronosequence reclaimed sites covering successional ages in the ranges 1, 4, 8, 11, and 13 years under forest and pasture ecosystems. The adjacent normal and unmined pasture and forest were used as a control for comparison purposes. The study site was located at the Red Hill Mine in east central Mississippi (approximately 33.3 N latitude and 89 W longitude), which is used by the North America Mining Company, LLC. Soil samples were collected from the reclaimed and unmined sites at 0–15- and 15–30-cm depth and analyzed for selected soil quality indicators. Results indicated that water stable aggregate and infiltration were increased, but soil bulk density and compaction decreased with increasing reclamation age. Soil penetration resistance was greater in the pasture than forest ecosystem. All reclaimed soils had less microbial enzyme activity than an unmined forest ecosystem; however, bacteria population level after 11 years since reclamation was similar to that of unmined forest soils. Soil organic carbon increased with increasing reclamation age strongly correlated with soil physical indicators and appears to be the main driving force during the development of soil physical and biological properties in the humid southeast.