Chemical, physical‐temporal and spatial changes in 25‐year‐old mine soils in Southeast Ohio
2022
Demyan, M. Scott | Smeck, Neil
Reclaimed surface coal mines afford an opportunity to study initial pedogenic processes. This study sought to determine pedogenic processes active in a topsoiled* surface mine over 25 years. Soils were taken at 108 points from three grids in 1979 (1 year) and 2004 (25 years post‐reclamation) across a 20 ha watershed. The upper darkened portion of the replaced soil (^A1, ca. 0–5 cm), lower portion of the replaced soil (^A2, ca. 5–15 cm), and spoil (^2C) were sampled. Exchangeable Ca²⁺ increased from 4.3 cmolc kg⁻¹ in 1979 to 8.2 cmolc kg⁻¹ in 2004, and exchangeable Mg²⁺ increased from 2.5 to 3.3 cmolc kg⁻¹. Soil organic carbon (SOC) increased from 0.59% to 4.05% providing evidence for humification and cycling of basic cations. SOC increases and structural development decreased bulk densities from 1.70 to 0.99 g cm⁻³ in the ^A1 and 1.70 to 1.24 g cm⁻³ in the ^A2. pH decreased in all horizons. In ^2C horizons, total sulfur decreased from 0.39% to 0.13% and electrical conductivity 3.34 dS m⁻¹ to 1.01 dS m⁻¹, indicating probable pyrite oxidation and salt leaching. Soils classified as Anthroportic/Anthrodensic Udorthents, as three representative pedons lacked cambic horizons. Mine soil variograms indicated higher spatial dependency in ^A1 and ^A2 horizons in 2004 than 1979 (decreasing nugget: sill ratios), whereas ^2C horizons had lower spatial dependencies in 2004. This suggests that surface horizons are more influenced by soil forming factors than spoil, which is more influenced by 'random' conditions of reclamation and not in equilibrium.
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