Soils of Pinus sibirica forests near settlements

Pinus sibiricaforests near settlements are formed on the rich habitats in the absence of competition from other forest species. Tree stands here have fast rate of biological processes and high productivity. These forests ecosystems inherit the background conditions of the environment and are formed in habitats with a wide variety ofmoisture conditions and soils. Most of studied P. sibirica forests at the south of Tomsk region are dedicated to landscapes subtaiga forest zone with zonal gray soils. In the north of forest-steppe zone P. sibirica forests are rarer and confined to the river valleys due to high standards of P. sibirica to moisture conditions. Complex combinations of soil cover in each P. sibirica forest patch is determined by proximity to river valleys. There are several levels of heterogeneity of soil. Zonal level is defined by climatic conditions. Regional level is defined by position in the macro-relief. Local level of inhomogeneity is related with the microreliefand soil position in the system of tree stand edificator. Zonal automorphic soils are typical of upland habitats. Accumulation - transitive or eluvial soils are typical of sloping positions. Semi-hydromorphic and hydromorphic soils are typical of accumulative positions. The patterns of distribution of soil are found in each patch of P. sibiricaforest, but in general, the soils ofslope positions are foundfor a large part of their area. Tree stand structure in biogeocenosis affects through redistribution of precipitation by crowns and litter inflow. Edificator influence of forests determines capacity offorest litter, sod horizon, bulk density of humus and humus content in the upper part of soil. The main factor of differentiation of the soil cover in South taiga is lithological. It is heterogeneity of the underlying rocks. The variety oflithological basis was analyzed by using combined indicator - the average diameter of fractions. The soil-forming processes and patterns of the soil profile were analyzed by distribution of silt fraction. The peculiarity of soils of Pinus sibirica forests is loose constitution and high aggregation of humus horizons. These facts create an optimal water-air and thermal conditions in the root zone. Basic soil characteristics determine the type and shape of Pinus sibirica trees and their productivity. Pure P. sibirica forests ofpark type with low resistance to pests and diseases are formed in rich soils, but stable P. sibirica forests of taiga type with complex structure are formed on podzolic soils. Modern degradation of P. sibirica forests near settlements occurs due to their accelerated development, high levels of anthropogenic pressure and the lack of renewal.

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