Abstract
Clear-cutting induces biogeochemical, ecological, and hydrological changes in the soil environment, especially in the conditions of climate change effect. This type of management affects soil carbon sequestration. In this paper, we generalize the effect of clear-cutting in mountainous mixed coniferous forests on the direction of organic matter transformation and the properties of humic substances. Soil samples of dystric Cambisols were taken two and ten years after clear-cutting (CC). Soil profiles located at the same elevation under forest cover without any harvesting were used as references. The contents of total organic carbon, total nitrogen, qualitative and quantitative characteristics of humic substances, as well as the mineralogical composition and the clay-associated C fraction, were analysed. Under mountainous conditions, clear-cutting in the mixed coniferous forest enhanced organic matter decomposition and decreased the low-molecular weight humic fraction. It also caused the accumulation of more stable humic acids, particularly in the upper soil horizons, and resulted in accumulation of humic substances with higher contents of C and O and lower H content in the first years after CC. Clear-cutting in the first two years reduced the aliphacity of humic acids in the topsoil. Ten years after harvesting, a significant increase in aliphacity in the Oa horizon confirmed organic matter recovery. Mixed coniferous forests are more resistant to biotic and abiotic disturbances, which is particularly important in the face of violent weather phenomena related to climate change. Thus, forest management plans should consider the conversion of spruce monocultures to mixed coniferous forests.