Scientific publications

The research of the organic matter in the soils forming over bedrock of varying mineralogical and chemical composition (from poor granites to nutrient-rich marbles, dolomites and shungite schists) has been conducted. To single out the effect of the lithological factor on the stock and composition of organic matter in the soils, sample plots were chosen so that they would lie in the same climatic settings (mid-taiga subzone of Karelia) and in forests with the same tree species in composition and age (40-80-year-old pine stands). In the areas where the bedrock is rich in composition, but deeply metamorphosed and, hence, weathering-resistant (e.g., porphyrites with titano-magnetite ore, or volcanic breccia), it takes very long for the soil organic matter to be transformed. The bulk of it is stored at the surface as the forest floor, with only a minor part found in the mineral body of the soil. The humus forming under such conditions is mainly of the fulvate type, i.e. with the composition dominated by fulvic acids. Less resistant rocks (e.g., dolomites) offer better conditions for biotic activity, and the rate of soil organic matter transformation is higher, as evidenced by the humic/fulvic acid ratio (> 1). Organic matter in such soils migrates massively down the soil profile to be deposited in the mineral horizons. Thus, the studies have shown that the composition of organic matter and its deposition patterns are influenced not only by the mineralogical and chemical characteristics of the parent rock, but also, quite significantly, by its weathering resistance.