Lesovedenie

The studied indigenous pine mesotrophic bogs are located in the Western Dvina district of the Tver region and have mixed atmospheric and groundwater supply with reduced water runoff. A comparative assessment of two mesotrophic biogeocenoses (blueberry-ledum-sphagnum pine forest (PP 1) and blueberry-sphagnum pine forest (PP 2)) is given by the parameters of age series of forest stands, dynamic successional position, regenerative potential, condition of trees and forest stands, volumes of woody debris, degree of infestation by wood-destroying fungi, characteristics of the composition and structure of peat deposit horizons. Mesotrophic forest bogs (Pyavchenko, 1963) belong to the primary biogeocenoses, have a tree layer of different ages, mixed species composition with an overwhelming dominance of Scots pine in numerical and volumetric characteristics. The closeness of the correlation between the volumes of trees and their age in age generations differs: for biogeocenosis PP 1, the correlation based on the linear and exponential approximations is almost absent, for biogeocenosis PP 2, the correlation is very close, almost functional, R2 = 0.93. This situation occurs due to the degree of uniformity of tree volumes distribution in age series. The structure and composition of natural regeneration in both pine mesotrophic bog biogeocenoses suggests the possibility of the mixed spruce-birch formation replacing the pine formation only under significant climatogenic-hydrogenous fluctuations affecting the change in edaphic conditions of growth of bog communities. The study explains differences in the volumes of wood debris by the stages of deadwood decomposition. The transitional peat deposits of both pine forests are similar in structure, but have differences in their thickness: 5.0 m under the blueberry-ledum-sphagnum pine forest and 3.0 m under the blueberry-sphagnum pine forest. While there are undeniable similarities in structure of peat deposits of the pine forests, some differences in ash content, degree of decomposition and density can still be traced, which can be explained by differing geomorphological positions and hydrological regime of both pine forests. For the first time, quantitative and volumetric characteristics of the tree stands and peat deposit horizons structures of native pine mesotrophic bogs are shown in comparative dynamics.

The paper presents the results of a comprehensive study of the structural organisation of indigenous sub-tundra’s spruce forests in the Pechora River basin in the northwest of the Komi Republic. The main components of the spruce phytocoenoses’ structure were analysed, including the size, age and spatial characteristics of the tree layer and the undergrowth. It has been established that stands of sub-tundra spruce forests are characterised by a high degree of variability in trees’ inventory indicators. The coefficients of variation in trunk diameters and heights reach 55 and 40%, respectively, even within a single species – Siberian spruce. Analysis of the age structure of tree stands revealed two types: relatively uneven-aged with a predominance of ascending series’ generations and absolutely uneven-aged with a group mixture of trees of different ages. The latter correspond to climax phytocoenoses with continuous self-reproduction. Spatial structure assessment conducted using the point process methods showed that trees in the stands are distributed mainly randomly, without pronounced aggregation. However, the undergrowth formed clusters, especially due to the seedling regeneration of birch. In the vertical structure of the canopy of sub-tundra spruce forests, both "diffuse" types of structure (trees vary in height, but are similar in the total height of the crown) and "regular at the bottom" types (trees vary in height, but the bases of their crowns are at the same level) are observed. The data obtained contribute to the understanding of the mechanisms of intact forest communities’ functioning in the Far North under the conditions of a changing climate.

The study demonstrates the influence of temperature variations, precipitation and the urban heat spot effect on the seasonal development of woody plants. Shifts in woody plants’ phenodates caused by temperature changes and associated with the urban heat island effect were determined. Synchronous phenological observations were carried out in 2019–2021 in the Ussuriysk forest district and the city of Ussuriysk (Primorsky Krai). According to the Timiryazevsky weather station, a significant trend of increasing average annual temperature was noted in the period from 2011 to 2023 at a rate of 0.15 ° С year-1. Comparison of the temperature regime in the city and in the forest confirms the presence of the urban heat spot effect. The difference in average monthly temperatures between the city and the forest fluctuated in the range of 0.2–2.5 ° С in 2019, and 0.1–1.9 ° С in 2020. The temperature in each month was higher in the city than in the forest. Differences in meteorological parameters of the forest and the city lead to a corresponding shift in the timing of the advancement of plants’ phenophases. Based on the results of comparison of the 8 species of woody plants’ phenological development in urban and forest conditions, it was found that on average the date of the phenological phases advancement in the city comes 5.2 days earlier, and for thermophilic southern species – 7.7 days earlier. Differences in the sums of temperatures required for the onset of a certain phase are within 1–80 ° С. Bird cherry is the best bioindicator of climate change in the conditions of Southern Primorye, as this is the species demonstrating the closest relationship between the sum of effective temperatures and spring phenological phases. Using published data of phenological observations in the study area, the average shift in phenodates in plants over 85 years was determined, which averaged 7 days. The duration of the growing season in Southern Primorye is determined by the average annual air temperature. A linear dependence was obtained, showing that with an increase in temperature by 1, the growing season is extended by 4.4 days, and this is primarily due to the shift in the beginning of the growing season to an earlier date.

Based on long-term studies of forest litters in various geographical zones, factorial, genetic and structural-functional approaches to their study have been proposed. The forest ecosystems of the north of the Western Siberia and the Russian Plain were picked as study objects. The analysis also includes the results of a study of the forest ecosystems litters in Primorye, Sakhalin, and Kamchatka. The factorial approach to the litters studying demonstrated the predominant influence of the forest type, its position in the geochemical landscape system, general landscape and moisture features. Analysis of geographical patterns showed that the lateral (non-stagnant) nature of soil moisture, providing an additional influx of oxygen and ash elements, is of significant importance for the genesis of litters of the humified type in the conditions of middle taiga landscapes. In conditions of stagnant moisture, regardless of the geography of the regions, litters develop according to the peat type. In the southern taiga, the conditions of watershed areas provide optimal prerequisites for the development of complexes of destructive, enzymatic and humified type litters. Climatic factors largely determine the rate of decomposition of organic residues in a geographical zones series, but the degree of this influence depends on the properties of decomposing materials. The role of the edificator tree in the spatial heterogeneity of forest litters was demonstrated, especially with regard to coniferous species. Intrabiogeocenotic variability of local environmental factors and, as a consequence, litter properties was found to be indicated by a living ground cover. The genetic approach is based on the consistent description and diagnostics of litter subhorizons, the genesis of which is used in the nomenclature of litters. This serves as the basis for the classification of litters. It is claimed that the validity of the presented classification has been shown in a wide range of bioclimatic conditions. The structural and functional approach, which provides for component analysis, allows us to assess the nature of the functioning of forest litters. The important role of the content and proportion of detritus and easily decomposable components, as well as the ratio of litter subhorizons stocks was revealed as a possible criterion for the features of forest litters’ functioning.

The decomposition of litter occurs in several stages, the most intensive of which is the primary stage. The aim of this is identifying the features of the initial stage of needles’ decomposition in a cowberry pine forest and its dependence on hydrothermal conditions and internal biogeocenotic differences. The trial plot is located on the territory of the Kivach State Nature Reserve in the middle taiga subzone of the Republic of Karelia. Decomposition of needles was carried out by laying bags with needles. The study of the features of decomposition of needles in different microgroups of ground vegetation during the first vegetation period showed insignificant differences within the standard deviation. It was found that the decomposition of needles in the cowberry pine forest in the middle taiga subzone reached 31.5 ± 3.5% during the vegetation period (120 days), 44.0 ± 1.4% during the annual cycle and 55.8 ± 5.1% during a two-year period. The use of the asymptotic model of Berg and Ekbohm showed an overestimation of the annual decomposition value by 10–3%. The proposed logarithmic model is based on two-year empirical data and gives an error of 3–5% in calculating the annual loss of needle mass.

The assessment of animals’ participation in the cycles of biogenic compounds allows to determine the key importance of species in the functioning of ecosystems and the strength of ecological connections within the biome. Such studies are especially relevant in the vast zone of boreal forests with diverse herbivore communities. The direct impact of wild ungulates on the chemical composition of a soil occurs primarily through feces and urine. The purpose of our study is to assess changes in the chemical composition of the soil under the influence of urine of the largest taiga herbivore – moose (Alces alces) in the north-east of the European part of Russia. During the period of snow melting, winter moose urine spots were marked on an overgrown field with a mosaic of tree-shrub vegetation. Soil samples were taken in two horizons (0–5 cm and 5–20 cm) under the points of moose urination and in the control. Standard soil indicators were analyzed: pH, organic matter content, NH₄⁺, NO₃^–, P₂O₅, K₂O, Ca, Mg. The decrease in acidity, high concentration of potassium oxide and some nitrogen-containing compounds were noted in the spring soil samples taken under the winter urinary patches. In particular, the concentration of ammonium in the soil under the influence of moose urine is 350% higher than the control soil location. Maximum changes in the chemical profile from the presence of urine was found in the uppermost soil horizon. The local concentrations of chemicals on the urinary patch create an anomalous soil chemical spot. By autumn, according to many indicators, the concentrations of urinary substances in the affected soil decrease to the background level, that is, rapid degradation and transformation of urine components occur in the soil during one warm growing season. No significant differences in the concentration of organic matter, calcium and magnesium in the soil were found between the soil samples from moose urinary patches and the control. It is calculated that all population groups of moose in Russia annually excrete 3.85 Mt of urine over a total area of about 700 km². The moose excretions increase the heterogeneity of the soil profile and contribute to the intensification of biogeochemical cycles.