Nitrogen and Carbon Reserves in the Soils of Spruce Forests of the Murmansk Region

Forest ecosystems play an important role in regulating the carbon and nitrogen cycles, serving as natural reservoirs of chemical elements. This study aims to obtain new data and refine existing information on carbon and nitrogen stocks in the soils of northern taiga forests. This information is particularly relevant for certain regions due to climate change and anthropogenic impacts. The focus on the Murmansk Region is due to the insufficient knowledge of carbon pools in the soils of northern forests, where specific temperature and hydrological regimes can significantly affect organic matter stocks. The article presents the results of a study on organic carbon (Corg.) and nitrogen (N) stocks in the soil of spruce forests in the Murmansk Region. The study object was Al-Fe-humus podzols in dwarf shrub‑green moss spruce forests in automorphic landscape positions. In July–August 2023, five sample plots were surveyed. Within these plots, soil samples were collected in the dominant elementary biogeoregions: in inter‑crown areas (dwarf shrub‑green moss) and under‑crown spaces (under Picea obovata Ledeb. and Betula pubescens Ehrh.). The study reveals the characteristics of the profile distribution of carbon and nitrogen stocks in the organogenic horizon (forest floor) and mineral horizons. It also demonstrates the accumulation of Corg. and N in the mineral layers at depths of 0–10 cm, 0–30 cm, and 0–100 cm. The highest reserves of Corg. and N in the forest litter were found under the spruce canopy. The total reserves (organogenic horizon + mineral layer 0100 cm) of Corg. in all studied biogeoregions are comparable and amount to 116,7–119,3 t/ha. The reserve of Corg. in the litter is 13,3–21,8% of its total reserves in the soil. The reserves of N in the organogenic horizon are comparable for the under- and inter-canopy spaces and amount to 0,63–0,70 t/ha. The total N reserves (16,4 t/ha) and N reserves (15,9 t/ha) in the 1-meter soil layer are maximum under the Betula pubescens crowns. In the intercrown spaces and under the Picea obovata crowns, the total nitrogen reserves are 14,5–14,8 t/ha. The N reserves in the litter are 2,9–4,9% of the total soil N reserves. Thus, the main reserves of soil nitrogen (up to 95%) and carbon (up to 82%) are located below the organogenic horizon and are found in the mineral layer of 0–100 cm.