Impact of forest fire on soil properties (review)

We examined changes in the morphological, physicochemical properties and features of the organic matter of forest soils impacted by wildfires on the territory of Russia. Morphological signs of pyrogenesis (pyrogenic horizon formation, partial charring of litter and illuviation of organic compounds) are most evident detected in the first decade after a fire. Ground fires in lichen pine forests, formed on Albic Podzols lead to complete burning of litter. Low intensity ground fires in sphagnum pine forests, developing on Histic Podzols, contribute to partial burning of litter (charring). Fires change the hydrothermal regime of soils, which is most clearly demonstrated for soils formed on permafrost soils / cryosols. Fires lead to hydrophobization of the upper mineral horizons, estimated from the contact angle of wetting. Resistant products of pyrogenesis (charcoals, soot) are retained in soils for several centuries. The most common changes in the physical and chemical properties of soils after fires are a decrease in acidity by 1–2 units of pH, an increase of saturation with base saturation. Fires increase aromaticity of soil organic matter. After fires, the content of polyaromatic hydrocarbons in soils increases, and the concentrations of water-soluble organic compounds decrease. Restoration of soil properties to the prefire state takes a decade to several centuries. The introduction of a universal subtype “pyrogenic” is proposed in describing the morphological characteristics of forest soils.