Minesoil Genesis and Morphology in a Spoil Chronosequence in Montana

Abstract Minesoils from 1 to 50 years old in southeastern Montana were compared to adjacent natural soils. Due to their maninfluenced origin, minesoils had several unique morphological properties which made them difficult to classify. Weakly consolidated rock fragments, common in minesoils, acted in part like soil in supplying water and in part like rock in preventing root penetration. Low chroma mottles were common in minesoils without the influence of a high water table. Organic C content from 0–10 cm soil depth reached levels found in natural soils within 30 years, but will not reach equilibrium at 20–50 cm for 400 years or more. Litter accumulation was common under pioneer vegetation on minesoils resulting in wide C/N ratios; reduction in available N; successional stagnation; and reduced plant community production. Soluble salts were leached downward in minesoils in tens of years, but thousands of years will probably be required for carbonate removal to occur in the upper 50 cm. Soil structure developed more quickly near the soil surface (10–50 years) than below 10 cm (50–200 years), and was attained sooner in clayey than in sandy minesoils. Many characteristics of minesoils are expected to always be different from natural soils. Well‐designed minesoils can be highly productive, however, in a few cases perhaps exceeding the potential of natural soils.