The problem of assessing carbon fluxes and pools in forests is acute due to climate change and contribution of forests to carbon reserves. The papers provides a comparative assessment of carbon ingress with atmospheric precipitation and leaching the dissolved organic carbon from soils under coniferous–deciduous forests of different types on sandy soil-forming deposits. The dominant types of coniferous–broadleaved forests of the Bryansk region, i.e., dwarf shrub–green moss pine forests, composite boreal–nemoral herbaceous pine forests and polydominant broadleaved nemoral-forb spruce forests are the objects of study. On average, over a three-year-long observation period (2016–2019), the carbon ingress with rain and snow was 60 ± 4 kg C/ha per year in shrub–green moss and composite pine forests; this turned out to be higher than in coniferous-broadleaved forests, where the carbon input was 47 ± 2 kg C/ha per year. The removal of organic carbon from organic horizons in polydominant broadleaved forests was four times lower (14 ± 4 kg C/ha per year) on average than in dwarf shrub–green moss pine forests specified by a thick litter (56 ± 22 kg C/ha per year), and 2.5 times lower than in composite pine forests (36 ± 12 kg C/ha per year). The cases of leaching organic carbon from the lower mineral horizons were scarce for different types of coniferous-deciduous forests and varied on average from 6 to 12 kg C/(ha year). The distribution of dissolved organic carbon in the soil profile shows a more efficient carbon fixation in the mineral part of soil profile in pine forests than in polydominant broadleaved forests.

The problem of assessing the impact of biodiversity on the climate-regulating functions of forests has fundamental character and great importance for sustainable forest management in the context of global climate change. On the one hand, climate changes affect biodiversity, on the other hand, it is biodiversity, as a provider of all ecosystem functions, underlies the mechanisms of adaptation to these changes. This paper aims to discuss scientific questions about the links between biodiversity and climate-regulating functions of forests, and to outline the prospects for these studies. It is shown that studies of the influence of plant and animal species – ecosystem engineers on forest ecosystem’s functioning, including climate-regulating processes and functions, are quite numerous. However, studies of the combined effects of the diversity of biota belonging to different trophic levels and groups on climate-regulating functions of forests of different types/different stages of succession are not carried out. In such studies, it is important to take into account both taxonomic, including genetic, and functional biodiversity as well as structural diversity of forests. Various concepts of forest management taking into account the conservation and restoration of biodiversity are considered. An important aspect of this problem is the assessment and prediction of relationships (synergy or trade-offs) between climate-regulating and other ecosystem functions of forests with different levels of biodiversity functioning in natural conditions and under the combined impact of natural and anthropogenic factors, including climate change, fires, and forestry regimes. It is shown that a promising approach to assessing and predicting the dynamics of relationships between different ecosystem functions of forests is the integration of mathematical models.

A comparative assessment of carbon accumulation in the soils of pine forests in western Russia (the Republic of Karelia, the Karelian Isthmus, and Bryansk region) developed on coarse-textured parent materials has been made. The total carbon stock in the litter and upper soil layer (0–50 cm) varied from 47 t/ha in the soils of pine forests of Bryansk region to 116 t/ha in the soils of pine forests of the Karelian Isthmus. It has been shown that the main factors of carbon accumulation in the soils of pine forests in western Russia were the climate, parent materials, vegetation, agricultural activity, and fires. The influence of climatic conditions has been clearly manifested in the levels of carbon accumulation in the litter and in the upper humus-accumulative soil horizons. In the pine litter within the zone of mixed forests (Bryansk region), the level of carbon accumulation was the lowest, whereas the litter layer of pine forests in the northern taiga (Karelia) has the highest stock of carbon. At the same time, the lowest carbon stocks in the upper mineral soil layers has been noted for the soils of northern taiga forests, which had no humus-accumulative mineral horizon. The variability of carbon stocks in the litter layer was largely controlled by the C/N ratio, as well as by the fraction of deciduous undergrowth and grasses producing high-quality litter. The influence of agricultural activity on soil carbon stock in pine forests was especially pronounced on the Karelian Isthmus with the high agricultural activity in the past, as well as in Bryansk region, where pine forests are formed from pine plantations. The effect of fires on soil carbon stock was most pronounced in heather and lingonberry pine forests of the northern taiga of Karelia.

A comparative assessment of the carbon stock in loamy soils (Albic Retisols) of coniferous–broadleaved forests on the Moskvoretsko-Oksky Plain and sandy soils (Albic Podzols) in the Bryansk region is given. The carbon accumulation in soils is related to the texture of their mineral horizons and biotic factors, such as the quality of litter and activity of earthworms. The forests on sandy soils were characterized by a high carbon stock in the plant litter, which is explained by the low biomass of earthworms. The carbon content was significantly higher in the mineral horizons of loamy soils owing to high share of fine particles. The carbon stock in the litter and mineral horizons of loamy and sandy soils turned out to be comparable, except for the sandy soils of mixed forests due to higher clay content. In the course of succession of the coniferous-deciduous forests on the loamy soil, the carbon accumulation in the litter was high only at the late stage due to the high input of spruce needles. The carbon stock in the humus horizons of the loamy soils varied due to changes in their density, which was regulated by earthworms. When comparing different succession stages/types of the forests on sandy soils, it was found that the carbon stock in the litter of the pine forests at the early stage of succession was significantly higher than that of the mixed and broadleaved forests. Trends of carbon accumulation in the mineral horizons of sandy soils were mainly explained by their thickness, which was related to the amount of percolating precipitation regulated by woody plants.

We have assessed the influence of vegetation on the labile characteristics (acidity, total carbon and nitrogen content, and available nutrients) of automorphic soils of polydominant coniferous–broadleaf forests and dwarf-shrub–green-moss pine forests of the Bryansky Les Nature Reserve. Despite the comparable gross and grain size compositions of soil-forming rocks, the differences of soils of these forest types are determined by the influence of vegetation, mainly by its ability to form litters of different quality and to regulate the amount of precipitation percolating through the forest canopy and contributing to the nutrient removal. Soils of pine forests have a higher acidity and lower contents of total nitrogen, organic carbon, and available nutrients than do soils of coniferous–broadleaf forests. The stand of pine forests has a low crown density, which leads to more intensive nutrient removal by atmospheric precipitation infiltrating through the soil.