Lesovedenie

Identification of the leading factors determining forest cover differentiation is a still understudied topic in ecology and biogeography. This study’s objective is to assess the contribution of natural and anthropogenic factors to the formation of modern forest cover diversity on the example of the Moscow region. As a result of classification of 1032 field relevés, 13 vegetation community types were identified based on the dominant forest-forming tree species and phytocenotic spectra of plants in subordinate layers. Using statistical methods, the heterogeneity of the identified community types’ floristic composition and the accuracy of their classification were assessed, and the ordination of communities in the ecological framework was done. The relationship of community types with biotopic local factors was analysed using Ellenberg scales. Most pairs of identified community types differed significantly by the results of Duncan’s test (p < 0.05) for all biotope properties. A list of indicator species for the identified community types (IndVal) was compiled. It was also shown that the most significant local factors determining the identified community types were soil acidity, nutrient abundance and moisture. At the upper spatial level, community variability was studied in relation to external environmental factors based on global spatial databases, and the relationship with individual forest cover fragmentation indicators was assessed. Among the most significant factors were the climatic ones (average annual temperatures and precipitation). Terrain (elevation above sea level) also significantly affected the composition of communities. Anthropogenic factors (distance from settlements, forest cover fragmentation) had a smaller impact on the differentiation of community types compared to natural ones.

In the subzone of the southern taiga, birch forests are the most widespread plant formation. Under the canopy of birch, undergrowth and the second layer of spruce are often found, which can serve as the basis for the restoration of economically valuable spruce stands. In such stands, birch is the dominant species, which has a significant impact on the development of the spruce population and on the course of succession processes. Without knowledge of the peculiarities of the birch forests formation, it is impossible to assess adequately the prospects of the spruce sub-canopy population. The research has been carried out for 20 years by the Institute of Forestry of the RAS on 18 permanent test plots (PTP) established by the Northern Forest Experiment Station (Yaroslavl region) in the prevailing in the region modal sagebrush-blackberry birch forests with a sub-canopy population of spruce. All growing trees were periodically surveyed at the PTP with measurement of the main biometric characteristics. The studies revealed that vertical structure becomes pronounced in birch forests aged 20 years. The studies revealed that vertical structure becomes pronounced in birch forests aged 20 years. Observed at this age can be the maximums of average periodic growth in height and in the sum of cross-sectional areas for birch trees of the first layer. The growth in the sum of cross-sectional areas of trees of the second layer always remains in the zone of negative values, which can be explained by the transition of some trees to the first layer as well as by them dying off. The age of quantitative maturity of the modal birch forests under consideration is 50 years, which corresponds to the age of birch and spruce stands in the middle taiga, but 10 years more than in normal stands. The stock of birch stem wood of the growing part of the modal birch stands of southern taiga is higher than that of complete birch-spruce stands of middle taiga, but less than that of normal birch stands. Regression relationships between a number of birch forests’ taxation characteristics and their age were established. In the course of successional processes in modal southern taiga birch forests there is a gradual decline of aspen and second-layer birch trees. Renewal under the spruce canopy leads to the formation of birch-spruce stands, in which spruce becomes the dominant species in the second layer of the stand in 120 years, and a small part of trees emerges the first layer. The age of 120 marks the beginning of birch forests’ decay.

In view of global climate change and biodiversity decline, long-term research in primeval forests escaped from timber harvesting is especially important. We aimed at analysing the dynamics of number and volume of standing dead trees (snags), as well as the patterns of tree mortality and longevity of snags in primeval middle-boreal spruce forests. The study is based on a database of tree inventories on the eleven permanent sample plots over 25—46 years. The volume of snags during the period from 1971 to 2019 varied from 0,4 to 164 m³ ha^-1 with an average annual “turnover” rate (the period from tree death to snag fall) from 0,07 to 32,7 m³ ha^-1 year^-1. In several biogeocoenoses, the peaks in tree mortality through decline after windthrows were observed, resulting in the stock of coarse woody debris being comparable to the growing stock of a forest stand. The rate and mode of tree mortality and the species distribution of snags depended on the site moisture regime, tree species composition and age structure of the forest stand. Before death, some trees were weakened for a period of up to 46 years. The time of tree weakening before death (the period from the moment when mechanical damage, traces of insect activity, diseases, etc. were noted in the tree, until the moment when a tree died) did not have a significant effect on the duration of snag longevity. The duration of snag longevity varied from 2 to 30 years or more depending on interrelated factors: tree species and size, moisture conditions, tree species composition of forest stand, and successional status of the biogeocenosis.

In light of large-scale logging in the regions of Central Siberia, the problem of restoring the hydrological regime in catchment areas seems to be very urgent. The Angara River basin is the most indicative in terms of forest disturbance. The purpose of this work was assessing the impact of the area of forest cover disturbed as well as of post-logging reforestation on the hydrological regime of the Angara tributaries using climate databases and remote sensing data. The paper analyses the runoff dynamics in four Angara tributaries (the Irkineeva, Chadobets, Mura, and Karabula rivers), whose catchment areas were subject to large-scale logging. To solve this problem, we used long-term runoff observations data from hydrological posts and precipitation data from meteorological stations in the region under study. The forest cover changes analysis in the studied catchments, taking into account the clearing areas, was carried out using the data from the Global Forest Change (GFC) 2000—2020 resource (https://earthenginepartners.appspot.com/science-2013-global-forest) and Landsat satellite images. The direction of the reforestation and the forest restoration processes were analysed based on our own forestry research and forest management materials. It was found that logging caused a decrease in the flow of the studied rivers from 1.5 mm (Mura River) to 4 mm per year (Chadobets River) over the past two decades. Relative equalisation of the flow is observed when 16—20 years old clearings are overgrown, when young trees reach the pole wood growth stage. The obtained results and numerical modelling of the runoff’s dependence on the area of forest cover disturbance showed critical values of the fresh cuttings’ share for maintaining the stability of water content of Angara’s medium and small tributaries. For example, for the smallest of the studied rivers (Karabula), the area of non-renewed cuttings should not exceed 2% of the catchment area. Cutting on adjacent units is possible only after the formation of closed young growth in the first cutting. The studies showed some certainty in studying of the conjugation of runoff dynamics and critical transitions of secondary phytocoenoses caused by a gradual change in the vegetation cover in the process of reforestation after disturbance of the forest cover in the catchment area.

As a result of constant changes in the structure of the vegetation cover, future scenarios of the rivers’ hydrological regimes after logging are determined by both further climate changes and the direction of vegetation successions.

Studying the plasticity of tree life forms helps to understand the mechanisms ensuring the stability of their populations in forest communities. The object of the study is the prostrate life form (trailing shrub, ‘stlanec’) of the pedunculate oak (Quercus robur L.). The aim of the work is to show the importance of prostrate form for the stable existence of oak populations in forest coenoses. The oak was studied in Nerussa-Desna Woodland. Field studies have revealed that the prostrate form of oak forms under limited illumination in bilberry pine forests, cowberry pine forests, green moss — cowberry pine forests, mixed-herb pine forests and cowberry-bilberry birch forests. Morphological analysis has shown that the prostrate form forms in several ways: lying down and rooting of the orthotropic trunk, of lower horizontal branches and shoots of the undergrowth, as well as of forming shoots of quasi-senile individuals. The prostrate life form is a manifestation of the oak’s phytocoenotic tolerance. The prostrate form is a variant of the undergrowth characterised by extremely low vitality. In this depressed state, the oak can exist under the forest canopy for more than fifty years. With improved illumination, the prostrate form first transforms into a semi-prostrate form, and then into an upright crown-forming tree. This demonstrates the optionality of the oak’s prostrate lifeform.

Boreal forests are the most important reservoirs of terrestrial carbon. Their wood makes up to 30—35 % of their overall carbon stock, making their inventory a task of national importance. The world practice of recent decades is scaling the forest inventory data using unmanned aerial vehicles (UAVs), which are an effective and inexpensive means of collecting information at the level of individual biogeocoenoses. The variety of survey and processing methods requires finding optimal approaches to wood stock inventory using UAVs. The article is dedicated to comparing two methods (Matlab — ML and TerraScan — TS) of estimating the number, height and projective cover of tree crowns by processing point clouds of laser reflections of different densities (100 and 2800 points / m²; ML₁₀₀, ML₂₈₀₀ and TS₁₀₀, TS₂₈₀₀). Lidar survey was carried out on three 50 × 50 metres sample plots. SP 1 — forest crossed by a stream; SP 2 — forest on a flat surface; SP 3 — forest bordering an oligotrophic swamp. The number of trees identified using ML₁₀₀ / ML₂₈₀₀ for SPs 1, 2 and 3 was: 55 / 66, 67 / 87 and 174 / 220; while using TS₁₀₀ and TS₂₈₀₀ resulted in following numbers: 66 / 95, 85 / 156 and 82 /166 respectively. The average tree height reaches 10—24 m, with little difference between the two processing methods at each site. The total projective crown cover for SPs 1, 2 and 3 was 2569, 2494 and 2059 m² in ML; 2091, 2424 and 1506 m² in TS. During remote assessment, only the first storey trees’ number could be estimated with a sufficient degree of completeness: for this task, the ML₁₀₀ method was sufficient. However, for a more comprehensive inventory of trees, including lower storeys, it is preferable to use TS₂₈₀₀, under the condition of an adequate selection of the minimum tree height parameter’s value.