Dynamics of Water-Soluble Carbon and Nitrogen Content in Soils in the First Years after Clearcutting

Logging is one of the main anthropogenic factors that change forest ecosystems. An experiment was launched to study the effect of logging equipment on soil properties after cutting spruce forests in the middle taiga of the Komi Republic, during which skidding trails with different number of wheeled vehicle passes (forwarder PONSSE ELEPHANT) were set. Carbon (C_ws) and nitrogen (N_ws) of water-soluble compounds play an important role in the global cycle of elements. The paper presents the results of observations over the water-soluble organic matter content in the soils of original forests (podzolic soils—Albic Retisols) and the soils at different technological sites of the logging area that have experienced different loads, i.e., cutting strips and skidding trails with three passes of logging equipment (podzolic soil), ten passes (turbozem), and passes followed by leveling (turbozem). A significant increase in total carbon was revealed in soils in the first two years after cutting. The greatest changes were registered in the upper mineral horizons (EL and TUR_cwd), in which the carbon content increased 3–6 times (0.32–2.2%) versus 0.45% in the original forest soil. A considerable rise in the C_ws content was found in organic and mineral soil horizons (up to 33.4 and 0.46 mg/g, respectively) after clear cutting, which thrice on average exceeds the initial values. The content of water-soluble nitrogen increases from 0.23 to 2.12 mg/g in the organic horizon two years after tree cutting. In the mineral horizons, the N_ws content varied from 0.003 to 0.020 mg/g after cutting (versus 0.002–0.011 mg/g in the original forest soil). It is shown that an increase in water-soluble carbon and nitrogen contents can be considered a significant criterion of changing soil organic matter due to logging activities, since their concentrations differ substantially from the initial values.