Biochemical Activity of Litter as an Indicator of Soil Quality in Pine Forests of Eastern Fennoscandia

Forest litter’s biochemical activity was examined in iron-illuvial podzols and podzolized podburs (Albic Podzols and Entic Podzols), considering (1) variations in edaphic and climatic conditions, and (2) levels of anthropogenic pollution. In the first case, blueberry (BPF), lingonberry (LinPF), and lichen (LicPF) pine forests in the middle taiga subzone and LinPF in the northern taiga subzone and at the boundary with the forest-tundra zone were studied. In the second case, soils from pine forests at different distances from the impact zone of the Pechenganickel Mining and Metallurgical Combine were analyzed. The study examined how the “ground cover–litter” system affected soil enzymes and chemical properties (pH, C, N, P, K, S, Cu, Ni). The forest litter in the middle taiga’s LicPF exhibited 1.5–1.8 times higher invertase and phosphatase activities compared to BPF and LinPF. The decrease in mean daily temperature by 2–3°C resulted in a corresponding decline in catalase activity by 58 and 69%, urease activity by 43 and 52%, and invertase activity by 51 and 28%. The activity of enzymes in the forest litter did not significantly vary with the level of copper and nickel contamination, suggesting a strong adaptive potential in the microorganisms-soil system. The discussion revolves around using soil biochemical activity for monitoring forest biogeocenoses.