Assessment of Carbon Pools in the Tree and Shrub Layer of Postagrogenic Forest Phytocenoses of Kenozersky National Park

An assessment of carbon pools in the components of the aboveground phytomass of the tree and shrub layer of the small-leaved stage of succession is presented for thickets of gray alder (Alnus incana L.) and goat willow (Salix caprea L.) with an admixture of birch (Betula sp.) growing in postagrogenic conditions on the territory of Kenozersky National Park. The studied biological communities were formed on abandoned arable lands with an age of up to 30 years in herb-rich forest vegetation conditions. It was found that the largest carbon pool accumulates in the 16-year-old herb-rich alder stand (31.11 t/ha) compared with the stock in the herb-rich willow stand undergoing successional replacement by gray alder (18.67 t/ha). The largest share of the carbon pool is accounted for by the stem wood fraction. The share of stem wood in the total aboveground phytomass of the overstory is 70.5 % in the alder stand and 66.7 % in the willow stand. The branch fraction occupies a secondary position in terms of carbon stock in the stands of alder (13.2 %) and willow (11.7 %). The share of carbon accumulated by the stem bark in the total carbon pool of the aboveground phytomass for both forest types is identical (11.1 %). The fraction of foliage accounts for the lowest share of the carbon pool in the first tier: 3.3% for willow and 3.6 % for alder. The carbon stock in the fraction of dry twigs is variable; for alder, this is the smallest share of the carbon pool (1.5 %), while in willow, the value increases to 7.3 %, which can be explained by the disintegration of the willow phytocenosis and its replacement by gray alder. In the carbon pool of the understory, the largest share is accounted for by the second-size trees and shrubs (64.9 % for the alder stand and 54.5 % for the willow stand).