Dynamics of Soil Properties and Carbon Stocks Structure in Postagrogenic Ecosystems of Southern Taiga during Natural Reforestation

The dynamics of some soil properties and carbon stocks in the main components of postagrogenic ecosystems were studied during natural reforestation in dependence on the lithological conditions and the type of former land use by the example of four chronosequences in Kostroma oblast. In the course of forest restoration, soil acidity increases and the content of exchangeable bases decreases in the upper part of the soil profile; this trend is more pronounced in sandy soils. The content and stocks of organic carbon dynamics are determined by the land use type, while the intensity of the postagrogenic dynamics is controlled by the native properties of soil. As forest vegetation is restored, a gradual differentiation is going on in the old arable layer by its carbon content and reserves, being most pronounced in 90-100 year-old forest soils. Approximately in 100 years, a total stock of organic carbon increases by 7-9 times in an ecosystem when overgrowing the arable land, and by 3.5 times in case of overgrowing hayfields. The structure of ecosystem carbon pool changes, i.e., the share of soil carbon decreases from 80 to 50% in 20 years after the land use had stopped, while the detritus share, on the contrary, increases up to 10% of the total carbon pool.