Carbon and Nitrogen Contents and Stocks in the Phytomass of the Ground Cover and Organogenic Soil Horizons in the Forests of Kivach Nature Reserve

In order to assess the carbon and nitrogen stock for such elements of the forest community as living ground cover and forest litter, studies were conducted in pine and mixed forests growing on soils of different types and moisture conditions on the territory of the Kivach State Nature Reserve. The carbon and nitrogen content in different types and groups of ground cover species and in organogenic soil horizons was determined. It was found that the carbon content in the vegetative organs (stems, leaves) of dwarf shrubs (bilberry, cowberry, heather) averages 53—55%, in sedges, grasses, forbs, green, sphagnum and polytrichous mosses, and fruticose lichens it is 45—46%. The nitrogen content in forbs, grasses and sedges averages 1.5—1.6%, in dwarf shrubs it is 0.9%, and in fruticose lichens it is 0.3%. The carbon and nitrogen content in the underground phytomass of the grassy-dwarf-shrub layer averages 51.3±0.3% and 0.51±0.03%, respectively. Depending on the habitat conditions, the total carbon stock in the living ground cover varies from 0.98 t/ha to 2.77 t/ha, nitrogen — from 0.017 t/ha to 0.030 t/ha. The carbon and nitrogen contents of the organogenic soil horizons change in accordance with the degree of decomposition of plant residues — from 53.1±0.6% and 1.1±0.05% in the fresh litter subhorizon to 39.3±0.1 and 0.9±0.07% in the lower organogenic horizons, respectively. Lower carbon content and higher nitrogen content are typical of mixed stands compared to pine stands. Carbon and nitrogen stocks reach their highest values of 50.5±4.8 and 0.92±0.19 t/ha respectively in waterlogged conditions. Nitrogen stocks in the organogenic horizons of mixed forests soils were larger (0.57±0.04 t/ha) compared to pine forests (0.47±0.03 t/ha).