Condition of Forest Soils Under Plantations Of Scots Pine of Various Age in the Forest-Steppe Zone of Trans-Ural

摘要

The paper contains an analysis of fertility changes in dark gray forest soils under man-made forests of Pinus sylvestris (L.) with the age of 15; 30; 45 and 60 years. The studies were performed in the territory of a forest enterprise located in Abatsky district of Tyumen oblast, in the northern forest-steppe of Western Siberia. Dark gray forest soil under a birch forest was used as a control. It has been established, that change in type of forest cover leads to changes in the species composition of the grass and shrub stratum. Humus state of the dark gray forest soils under man-made pine forests gradually deteriorates. Humus content reduces to 5.4% in the case where pines reach 60 years of age, while in the control plot under natural vegetation it amounts to 7.4% of soil mass. Qualitative composition of humus also gradually deteriorates: A fulvate-humate type is substituted with a humate-fulvate one, with low nitrogen enrichment. It has been established, that leaching is amplified under man-made pine forests with the age of under 45 years. Subsequently (60 years), podzolization starts in the dark gray forest soil, manifesting as destruction of soil adsorbing complex and increased acidity of the humus layer. In 45 years, base saturation decreased from 77% to 71% of the cation exchange capacity. Change in the humus state and chemical properties had a negative impact onto agrophysical properties of the dark gray forest soil. Water stability of structural aggregates gradually reduces from 65 to 42% with increased age of pine, while bulk density increases to 1.27 g/cm3. To prevent loss of fertility soils in Northern Trans-Ural, it is recommended to thoroughly analyze the plots planned under coniferous trees, to avoid their planting onto dark gray forest soils or soils similar in fertility. When moving such soils into arable lands, special measures are required for radical improvement in fertility (application of fertilizers, chalking) with subsequent sowing of perennial herbs.