Estimation of Carbon Stocks in Forest Litter of Middle-Taiga Forests of Eastern Fennoscandia

The forest floor is an integral component of forest soils, which constitutes a significant yet underaccounted terrestrial carbon pool. Comprehensive studies were conducted at a test site in the Kivach State Nature Reserve, which represents little disturbed middle-taiga ecosystems of Eastern Fennoscandia. Forest floor properties were studied following the methods guidelines of the project “National system for monitoring the dynamics of climate-active substances in terrestrial ecosystems of the Russian Federation”. Organic carbon content (С_org) was determined using Perkin Elmer 2400 Series II CHNS/O Analyzer (USA). The forest floor is a heterogeneous formation with quite variable composition and state. There predominantly (80% of all sampling points) forms a fermentation-type raw-humus forest floor with average thickness of 5.9 ± 0.2 cm and a stock of 49.8±1.9 t/ha in the study area. Organic matter is lost gradually in the course of dead plant biomass degradation, so С_org content in the dwarf shrub–true moss habitats predominating at the test site was the highest in the top layer of the forest floor, OL, reaching 52.8 ± 0.6%. Carbon content in the lower floor subhorizons declined to 40.8 ± 2.0%. Where the proportion of forb species increased, average С_org content significantly decreased, to 19%. Average estimated forest-floor С_org stock in the studied ecosystems is 20.9 ± 0.9 t/ha. It exhibited high spatial variation of 1.5 to 45 t/ha. The predictors of forest-floor С_org variation in the study area include land cover characteristics, dominant tree species, and location relative to the tree. Thorough estimation of the contribution of forest-floor carbon is necessary for accurate quantification of the stock of this pool within the new national system for monitoring carbon pools and greenhouse gas fluxes.