Boreal soils on hard gypsum rocks: Morphology, properties, and genesis

The genesis of soils developed from hard gypsum rocks in the northern taiga of European Russia is considered. These soils are formed by the following processes: surface accumulation of a low-ash litter and raw humus, humus formation from roots and fungal hyphae, local migration of humus compounds, physical disintegration, dissolution, leaching, and local accumulation of gypsum in the form of coatings. Pedogenesis on hard gypsum is a model of a bio-abiotic exogenous process that does not form stable mineral products. The existence of the soil profile is possible provided that the rates of physical disintegration of hard gypsum rocks and formation of loose gypsum fine earth are higher than the gypsum dissolution rate. The synthesis of calcium carbonates in the soil profile that is often mentioned in literature is not observed: calcite in calcareous varieties of gypsum-bearing soils is inherited from the parent rock.