Physical Properties Dynamics of Podzolic Soil in the Naturally Regenerated Cutover Areas

Abstract

The research relevance is driven by the need to study the patterns of changes in the physical properties of soil for prediction the recovery period after anthropogenic impact. The aim of the research was to establish the space-time patterns of changes and restoration of the podzolic soil physical properties during natural regrowth after cuttings. The study objects are located in the taiga forest zone on small-scale clear cuttings with fellings of 5, 18 and 28 years old. The initial plots are represented by the mature stands of blueberry forest with pine domination. Cuttings were carried out with the use of gasoline chainsaws for trees felling, and a skidding tractor for skidding. Clearing of cutting areas was realized simultaneously with timber harvesting by laying slashes on the skidding trails. In order to establish current characteristics of the studied areas, the evaluation of natural reforestation was carried out by laying out 215 test sites (5 x5 m) along the transects. In order to determine the soil physical properties on technological elements of cuttings (cutting strip, skidding trails) and control 288 samples were selected: 96 of forest litter (O), podzolic (E), illuvial (BF) soil horizons each. The results obtained at different times of cuttings have shown that the physical properties of sandy soils are dynamic over time. In 5 years after cutting soil compaction is detected, especially on the skidding trails, which affects the increase in bulk density (by 15-59 %) with a decrease in total porosity (8-11 %) and porosity of aeration of the upper horizons (8-23 %). Reliable compaction is observed in the forest litter and podzolic horizon, while in the illuvial horizon such difference is not proven. In 18 years soil compaction is detected. However, there are processes of soil decompression which are related to active reforestation of tree species and period passed after cutting. In 28 years the physical properties of soil were restored to their original values. We have established a moderate correlation between the bulk density of soil and cutting age (r = -(0.44 +/- 0.11)), as well as between the bulk density and the number of natural reforestation samples (r = -(0.31 +/- 0.10)), which contribute to soil decompression after cutting.