Carbon stocks were calculated in different components of bigeocenosis (soil, living ground cover, forest floor, undergrowth, underbrush and forest stand) using the example of a selected chronosequence of fallows (4 sample areas of different age, yrs: 16, 25, 63 and 130) in the Kargopol district of the Arkhangelsk region (middle taiga subzone, residual carbonate soils). The structure of carbon stocks of the forming plantations and its changes with the fallow age is estimated. It was found that a natural increase in carbon stocks and its redistribution between the soil and the forming phytocenosis occurs in the process of succession during the afforestation of arable lands. In plantations growing on young fallows, more than 86 % of the carbon stock is represented by carbon from the arable soil horizon. During the colonization of the fallow by forest vegetation the share of this pool decreases and already in the middle-aged 63-year-old forest it is 22 %, and in the mature 130-year-old forest it is only 7.6 %. In the structure of the total carbon stock in the middleaged plantation, the share of the stand reaches 69 %, and in the mature 130-year-old stand it is already 90 %. In plantations on young fallows, the structure of the main components of biogeocenosis (soil carbon, ground cover carbon and tree layer carbon) is characterized by a ratio of 9:1:0, whereas in plantations on old fallows of 63 and 130 years it is 2:0:8 and 1:0:9, respectively. The undergrowth and underbrush of the studied chronosequence are characterized by the small shares of carbon, which do not have a significant value in the structure of the ecosystem carbon pool. Forest floor in forming forest stands contributes significantly to the carbon structure of the biogeocenosis, although the total biogeocenosis carbon pool is 3–4 % and does not contribute to an increase in soil carbon stocks. In the system “soil – forest floor – living ground cover” the share of soil carbon decreases from 91 to 76–77 % with the increase in the age of plantation, while the share of formed forest floor in the middle-aged and mature forest is 16 and 20 %, respectively. In plantations on young fallows the ratio of these components of biogeocenosis is 9:0:1, whereas on old fallows it is 8:2:0. Leaving arable land on residual carbonate soils for self-overgrowth with forest vegetation and formation of forest plantations on them in the middle taiga subzone will lead to a gradual decrease in the carbon pool in the soil, but will contribute to the sequencing of carbon in the phytomass of perennial woody vegetation and in forest floor. These two components of biogeocenosis will serve as a sequenced carbon depot, supporting the biological cycle.
Effects of litter traits, soil biota, and soil chemistry on soil carbon stocks at a common garden with 14 tree species
