Currently, there is no consensus on how growing conditions affect the heartwood formation in Scots pine. Comparing the results obtained by different authors is difficult due to methodology differences and poor descriptions of the objects used. We selected two sample plots in (1) a blueberry pine forest on nutrient-rich and moist soil and (2) a lichen pine forest on nutrient-poor and dry soil and performed their detailed characterization. The sample plots were located 22 km apart in the middle taiga subzone (Karelia Republic, northwest Russia). In each sample plot, we selected five dominant trees (model trees), from which we took cores at different trunk heights (0.3, 1.5, 4.5, 7.5 and 10.5 m). The cores were treated with 2,6-dichlorophenolindophenol to identify the heartwood zone. Additionally, samples were taken to study the structural features of the transition zone between sapwood and heartwood. In both forest types, the number of heartwood rings depended on the cambium age, and the patterns of parenchyma cell death did not differ in the transition zone. These facts point to a predominantly internal regulation of the heartwood formation in Scots pine. The heartwood radius and its proportion on the cross-sections were significantly higher in the blueberry pine forest than in the lichen pine forest, despite the relative values of the annual ring width. Further research is needed to develop successful Scots pine heartwood width models under a wide range of conditions.

The study was carried out in the Kivach Nature Reserve (62°17′ N, 33°58′ E) from September 2019 to October 2022 in the mature middle-taiga spruce forests on Albic Stagnosols developed from varved clays. The dynamics of litter decomposition was estimated by the litterbags method. The samples of ten different litter fractions were studied: needles, leaves, bark of the dominant tree species (Picea abies, Populus tremula, Betula pendula), and leaves of a subshrub (Vaccinium myrtillus). The sample mass loss and changes in chemical composition of the plant material were analyzed over 9, 14, 28, and 38 months of the experiment. The impact of different factors on the litter decay rate was studied, taking into account its volume, diversity, and quality. We estimated the rates of litter input and decay, as well as the forest floor turnover rate in relation to the parcella (unit of the biogeocenosis horizontal structure) heterogeneity. Forest floor volumes varied among zones of the tree phytogenic field from 26 to 108 t/ha. The forest floor turnover period was between 13–14 and 34 years in the spruce forest studied.

The properties of a sandy Ferric Podzol over fluvioglacial deposits and the root mass of its 0–20 cm layer with Pinus sylvestris L. fine roots (≤3 mm in diameter) have been studied in a mid-taiga cowberry-type pine stand. Keeping in mind the structure of the phytogenic field of a tree, the study is subdivided into trunk, crown, and gap zones. The root mass of the forest floor and the mineral horizons are found to change in different directions in the these zones. In the forest floor, the trunk zone is more saturated with roots than the gap zone, while the trend in the soil mineral layer was the reverse. The highest root biomass is associated with sites that are the richest in soil nutrients and organic matter (NPKC). The cellulolytic activity and ecophysiological parameters of the microbiota vary in the studied horizons. Cellulolytic activity in the forest floor is the highest near tree trunks, while the spatial variation of this parameter in the mineral body of the soil is less pronounced. A correlation is detected between the contribution of root respiration to total СО₂ emissions from the soil surface and the biomass of fine roots (≤3 mm) in the 0–20 cm soil layer. The effect of the soil thermal regime on root mass in different zones of the phytogenic field is studied. Soil temperature variation due to the redistribution of solar energy by the canopy results in a higher root mass in areas receiving more heat. The zone with better heated soils is the canopy gaps. The effect of the temperature of the root mass of the soil is more explicit in the mineral layer. The results of this study can be used in environmental monitoring and in predictive assessments of the effects of climate change on boreal forest ecosystems.

In an old-growth bilberry spruce forest (Republic of Karelia, Kivach Nature Reserve), an assessment of the main components of the carbon cycle was carried out, and the net carbon balance was calculated using a stock-difference method. Based on the data from the forest stand measurement surveys of 2016 and 2022, the net primary production was calculated to be 3.38 t C/(ha year). During 3 years of year-round measurements of CO₂ emissions from the soil surface, estimates of annual CO₂ fluxes were made. The root and microbial respiration was separated. Because of heterotrophic soil respiration, 3.83 t C/(ha) year) enters the atmosphere, and due to coarse woody debris (CWD) respiration, it is 0.23–0.71 t C/(ha year). An analysis of the influence of environmental factors on the CO₂ emissions of soils was carried out. The seasonal dynamics of soil respiration by 45–50% was determined by soil temperature at a depth of 10 cm. Soil respiration during the cold period from November to April amounted to 15–22% of the annual CO₂ flux, depending on the spruce forest facies. The share of root respiration on average amounted to 27% of CO₂ emissions from the soil surface. Monitoring the formation of net primary production and CO₂ emissions in old-growth forests, as well as an analysis of factors influencing these processes, is of great importance for obtaining both modern carbon balance estimates and predictive estimates made using mathematical modeling methods.

МИКРОБИОЛОГИЧЕСКИЕ ОСОБЕННОСТИ ПОЧВ В РАСТИТЕЛЬНЫХ МИКРОГРУППИРОВКАХ СРЕДНЕТАЕЖНОГО СОСНЯКА БРУСНИЧНОГО В КАРЕЛИИ