Changes in Acidity and Cation Exchange Properties of Spruce Forest Soils after Damage by Bark Beetle

Changes in the acidity and cation exchange properties of soils in spruce ecosystems after the death of spruce as a result of an outbreak of the bark beetle (Ips typographus) in the coniferous-broadleaf forest zone (Moscow oblast) have been studied during long-term monitoring. The studies have been carried out in three types of forest ecosystems developed on eluvozems and soddy eluvozems on the two-layered parent material—mantle loam underlain by glaciofluvial sand—in 2008, 2019, and 2023, using uniform methods in accordance with the recommendations of the international monitoring program ICP Forests. Soil samples were collected in a stratified random manner in 30 × 40 m plots in organic layer and 0−5, 5−10, 10−20, 20−40 and 40−80 cm mineral layers. The soils have been characterized by a slightly acidic and acidic reaction, low cation exchange capacity and low base saturation. Over a 12-year period after the bark beetle attack, there were ambiguous changes in pH, an increase in exchange acidity and cation exchange capacity, enrichment of soils with exchangeable bases, and their redistribution in the soil layer. The organic layer and 80-cm mineral soil layer accumulated 560–1080 and 100–230 kg/ha of exchangeable calcium and magnesium and lost 140–370 kg/ha of exchangeable potassium with maximum changes in the soddy eluvozems of the most damaged complex spruce forest, which was replaced by a linden forest. The further dynamics of nutrients in soils and the need for forestry measures will be determined by the direction and rate of restoration of plant communities.