Dynamics, Structure, and Functional Activity of Microbial Biomass in Soils of Restoring Felled Areas in Fir Forests of the Yenisei Ridge

The dynamics, structure, and functional activity of microbial biomass have been studied in soils of felling areas in southern taiga fir forests (the Yenisei Ridge, Krasnoyarsk krai), which are at different stages of natural regenerative successions. The top organomineral horizons of soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) of the after-felling regeneration succession (with the stage of secondary birch forests) is characterized by an increase in the content of carbon of microbial biomass (C-mic) and in the intensity of basal respiration from new felling to the stage of dense young forest. In the soil of the dense young-wood stage, the total reserves of C-mic (170 g C/m(3)) and microbial CO2 production (528 mg CO2-C/m(3) per hour) are the highest and exceed the control by 80-85%. In the humus-accumulative soil horizon of the studied succession series, there is a tendency for a decrease in the portion of fungal substrate-induced respiration and in the fungi to bacteria ratio in comparison with the control. In the middle-aged deciduous forests with dark-coniferous undergrowth, all the considered parameters of microbial complexes decrease but remain higher than the control. A trend for a decrease in C-mic and basal respiration is revealed in the profile of soddy-podzolic soil of the regeneration series without species change over an eight-year period. At the stage of fir dense young forest, all ecological-functional parameters of the microbial complex become closer to the control small-grass-true-moss fir forest.