Prodrssive soil succession after thinning in northern taiga bilberry spruce forest

Damage to the top soil layers during logging operations can be of various forms (compaction, mixing, pressing, etc.) and of a long-term character. The recovery of the morphological characters and the structure of the soil profile of the native soil can take decades or have irreversible effect. We have studied the soil damage during two-stage (1973 and 2002) conversion thinning operations in the spruce forest with blueberry cover in the northern taiga (tree-length log skidding, TDT-55 tractor). The types of damage that stay during the progressive succession for 50 years and have signs of disturbances due to the logging operations were identified. The mosaic structure of the mixed bedrocks still continues to exist. The forest litter pressed by the heavy machines is replaced by the newly formed one. And at the same time, the organic bedrock of the medium degree of decomposition, which is untypical for the native podzolic soil, is preserved. Mixing by tractor tracks and the formation of mixed bedrock is the most common disturbance of the upper bedrock during logging operations due to insufficient coverage of the skid roads by felling residues. The amount of such damage to the soil is 77 % and 79 % in the skid roads of 1973 and 2002, respectively. But the depth of damage is small, which is 10 cm on average, with fluctuations up to 22 cm. In nano- and micro-depressions, the processes of peat formation and gleying develop. The number of locations with the genesis of bog soils is gradually increasing. On the skid roads of 1973 the proportion of wetlands is 2,5 times higher than in the skid roads of 2002 (86,9 % and 37,3 %, respectively). The long-term soil disturbance in the structure of the soil profile makes it necessary to develop classification approaches to improve the analysis of anthropogenic disturbed soils in cutting areas. The classification units are suggested