Contemporary Problems of Ecology

This paper addresses the effects of climatic limiting factors (precipitation and air temperature) on the radial increment variability of Scots pine (Pinus silvestris L.) growing in the Voronezh State Biosphere Reserve under the conservation regime conditions. A natural 200-year-old pine stand belonging to the grassy pine forest with oak type was studied. The following analyses have been performed: a mathematical analysis of the strength and frequency of the relationship between the monthly precipitation amounts and average monthly air temperatures (based on the data of Voronezh and Voronezh Nature Reserve meteorological stations), as well as radial increments of the Scots pine throughout the period of 80 years. It was established that the sums of precipitation in April and especially in May have the maximum effect on the radial increment of Scots pine (spring wood). The precipitation in July–August significantly affects the late wood growth. A strong correlation between the radial increment and September and especially October temperatures of the current year (r = 0.43) and the previous year (r = 0.40) was identified. In addition, a negative correlation between the radial increment and summer temperatures was established. The correlation ratio of the relationship between the meteorological factors and radial increment was considerably higher than the correlation index, which confirms the nonlinear nature of this relationship. Based on the cyclical dynamics of the radial increment of Scots pine (11- and 34-year cycles), models have been built using two forecasting methods (Caterpillar Singular Spectrum Analysis (SSA) and an additive increment model described by a sinusoid function with a given period), and an increment forecast for the 10-year period was produced. According to the models, the radial increment is going to decrease in 2018–2019, increase in 2021 ± 1, and decrease again in 2024 ± 2.

Taxonomic status of birches (Betula pendula, B. pubescens or their hybrids) is identified by molecular genetics assay of the ploidy level using SSR-markers in moist and peatland forest types. Studies are performed on experimental forest sites of the Institute of Forest Science in the center of the East European plain. B. pendula × B. pubescens hybrids accounted for 11% of the combined dataset. Thus, the birch hybrids are essential components of natural communities. We demonstrate for the first time that B. pendula is predominant, the hybrids are rare, and B. pubescens occurs sporadically on oligotrophic peat bogs. B. pendula grew in the canopy while B. pubescens and the hybrids grew in second story of moist blueberry pine forests. Identification of birch species using keys for the flora species is proven to be confusing due to the occurrence of different combinations of traits. All genetically identified B. pendula trees had twigs growing upwards, without pendulous traits.

Experimental assessment of the fire-induced effect on reproductive structures of Pinus pallasiana is conducted using the material from the natural stands in Crimean Mountains. Vital functions of the seeds are found to be partly preserved in cones exposed to fire. Probability of the seeds’ survival following the heat shock strengthened with the cones’ length, as well as the relationship between the seeds resilience level and weight as compared with control samples is shown. Fire is shown to act as a factor of selection by seed weight and cones size in natural P. pallasiana stands. Therefore, clear-cutting of burned intact stands eliminates the biocenotic component involved into a system of natural mechanisms of post-fire recovery of forest communities. The clear-cutting changes the pathway of natural selection based on resilience to fire, as well as impairs and delays the recovery of indigenous stands in burned natural populations of P. pallasiana.

This paper presents the results of analyzing the state and dynamics of damaged vegetation from satellite images of high and ultrahigh spatial resolution. This study was conducted based on the example of the site of coniferous forests in the Lower Angara region (Krasnoyarsk krai), where a large outbreak of the Siberian moth took place in 1944–1995. The remote assessment of the state of dark coniferous forests revealed the trends of the SWVI (or NDMI) and NDVI indices that characterize long-term changes in the vegetation cover over the period 2000–2018. The SWVI index is the most informative indicator: a sharp decrease in average values and increase in the coefficient of variation of the index are noted for dead and severely damaged wood stands (crown defoliation of more than 75%). The area of dead forests was calculated according to the difference images of the indices (ΔSWVI) with the threshold criterion lσ (the standard deviation). In 2000, the area of forests that died under the impact of the Siberian moth was approximately 19 200 ha. Alter two major fires in 2004 and 2011 and as a result of destructive factors combination, the area of dead forests increased up to 20 400 ha by 2017–2018. Reforestation within the boundaries of dead stands was estimated from the classification of Landsat images (June 20, 2017; June 23, 2018) by the Random Forest algorithm using the selection of templates from detailed Resurs-P images with a spatial resolution of 1 m (Geoton-LI—July 22, 2015 and December 3, 2018), which were taken during different seasons. The classification proved to be highly reliable (Kappa index is more than 0.9). The areas of classified deciduous and coniferous stands, deciduous and mixed stands with mainly coniferous regrowth, grass–shrub vegetation, and barren soil were calculated. Natural regeneration of mainly coniferous undergrowth occurred in 17% of the damaged area, and deciduous regrowth occurred in approximately 10% of the area 23 years after damage by pests. The area damaged by the moth affected reforestation: the larger the area of the outbreak, the higher the share of open lands with grass and shrub vegetation (it accounts for more than half of the area for the large outbreak and approximately 45% for smaller outbreaks). Regrowth was found in proximity of patches of stands and deadwood in the sites unaffected by large fires. Frequent fires in the territory of moth infestation limit the process of reforestation; therefore, most of the vegetation was at the initial stage of the succession cycle.

The contribution of bark, as a phytomass fraction, to nutrient cycling is studied insufficiently. This study followed six-year dynamics of physical and chemical characteristics of bark residues after clear cutting. The amount of bark present in logging slash was found to be 20.8 m³ ha^–1, or one fifth of the volume of coarse woody debris, which varied from 105 to 127 m³ ha^–1. The initial area-specific mass of bark was 0.601 g cm^–2 for aspen, 0.346 g cm^–2 for pine, 0.446 g cm^–2 for birch, and 0.233 g cm^–2 for spruce. The initial density of bark varied in the range of 0.51–0.71 g cm^–3 for aspen, 0.56–0.80 g cm^–3 for birch, 0.39–0.64 g cm^–3 for pine, and 0.60–0.73 g cm^–3 for spruce. The initial concentrations of nitrogen and carbon were 0.23–0.53% and 42–48%, respectively. The changes over time in specific mass, phloem percentage, and bark thickness depended on a particular tree species. The rate of mass loss was the maximal in spruce bark, whereas birch bark showed the maximal rate of phloem loss. The specific mass of bark decreased by 32–38%, the density by 10–17%, and the phloem percentage by 78–99% after six years since cutting. The concentrations of nitrogen and carbon in bark did not change during decomposition. Therefore, the bark layer on a soil surface partially compensates for the nitrogen losses caused by removal of logged wood.

Forest cover dynamics derived from detailed archival and recent satellite images was studied in the southern forest–steppe within Belgorodskaya Oblast, Central Russian Upland. We analyzed data from 5 sites of the total area of 1722 km², representative for diverse environment of the region. The forest cover increased by 31% during 1970–2014. Fragmentation of lands with forest cover was noted. Number of separate woodlands has increased by 87% and the mean size of woodland has decreased from 13.0 to 9.2 ha. Mean linear movement of the forest margin towards steppe tended to decrease from northwest to southeast. The largest advance of 34.3 m of the forest margin was found in the humid western part of the region, while it was as small as 15.0 m in dry southeast. Mean distance of forest advancement since 1970 was 24 m, as measured at 1285 study sites. The distances of forest expansion significantly differed between forest–steppe and steppe domains of Belgorodskaya Oblast. The expansion cannot be attributed to northern or southern exposition of the forested slopes of river valleys and ravines.