Anthropogenically induced climate change largely affects the functioning of vegetation communities worldwide. In the world's largest land biome, the boreal forest, a persistent decoupling of tree growth from rising summer temperatures has been recorded in recent decades. This so-called ‘Divergence Problem’ (DP) has been studied over the past 30 years, yet the causes and spatial patterns within the boreal forest zone are not well understood. Here, we present tree-ring evidence on varying DP in Larix gmelinii from the globally northernmost forest island on Taymyr Peninsula and Larix sibirica from the southern taiga in central Siberia. Tree-ring width and maximum latewood density data reveal DP to be substantially stronger in the south indicating that growth-climate relationships in Siberian larch passed beyond a tipping point under warmer climate and increased anthropogenic pressure. In the north, the temperature signal remained strong and temporally stable underscoring the skill of tree-ring chronologies for long-term climate reconstructions. These findings highlight the heterogeneity of tree growth responses to global warming within the boreal forest zone, from which spatially varying consequences for carbon and water cycle dynamics must be expected. Our study emphasizes the importance of updating tree-ring chronologies in remote regions within boreal forest zone to foster understanding of spatiotemporal patterns in biomass allocation, permafrost degradation, and DP across this large biome.

The article presents the results of investigation of antitumor properties of platinum–arabinogalactan complex. We showed the ability of the complex to inhibit the growth of Ehrlich ascites tumor cells. It is found that the distribution of the platinum–arabinogalactan complex is not specific only for tumor cells in mice. The complex was found in all tissues and organs examined (ascites cells, embryonic cells, kidney, and liver). The mechanism of action of the arabinogalactan–platinum complex may be similar to cisplatin as the complex is able to accumulate in tumor cells.

Influence of growth conditions to the wood structure was researched on three species of conifers from various topoecological conditions in forest-steppe zone of Khakasia. By correlation analysis of climatic parameters (average temperatures and precipitation amounts on ten-day periods) of growth seasons and structure parameters of wood rings (tree ring width, maximum density, radial size of tracheids and thickness of cell walls) was revealed that at different conditions of growth significant transformation of climatic signal depending on the topoecological conditions and specific features of tree species takes place. It is shown also that the main target for external signal is cambial zone; subsequent processes of cells differentiation and their result are less depending on external conditions. Nevertheless, cells parameters and particularly their combination at trees from different topoecological conditions allow to receive additional and more detailed information about climatic features of growth season and to reveal “key” intervals of season, when climatic factors can be evaluated quantitatively.

Processes of xylem formation in Dahurian larch have been studied at three sites differing in the hydrothermal regime of soils in the permafrost zone of Middle Siberia. It has been found that the start and end dates of different phases of tree ring formation may differ between the sites by up to 14 days, depending on site conditions. The data obtained contribute to knowledge of possible changes in larch forest phytomass production and provide the possibility of predicting its dynamics under conditions of climate change.

Изучены процессы формирования ксилемы лиственницы Гмелина, произрастающей в криолитозоне Средней Сибири на участках, отличающихся по гидротермическому режиму почвы. Результаты наблюдений показали, что начало и завершение различных фаз формирования годичного кольца у деревьев из разных топоэкологических условий отличаются по срокам до 14 дней. Полученные данные расширяют знания о возможных изменениях продуктивности лиственничных насаждений, а также позволяют составить прогноз ее динамики в связи с климатическими изменениями.

Chromosome numbers for some species of Central Asia steppe shrubs are given: Rhamnus erythroxylon Pall. (Rhamnaceae), Caragana buriatica Peschk. (Fabaceae), Amygdalus pedunculata Pall., Armeniaca sibirica (L.) Lam. (Rosaceae), Atraphaxis pungens (Bieb.) Jaub. et Spach, and A. frutescens (L.) C. Koch (Polygonaceae). Chromosome numbers of some species were determined for the first time. A comparative analysis of adaptive properties of polyploidy and diploid species has been conducted. It was established that natural polyploids are more adaptive to existence in extreme conditions. They possess a high potential for survival and are characterized by a higher level of intraspecific polymorphism, abundant flowering and fruitification, ability to propagate both via generative and vegetative means, and high seed germination.

This study addressed distribution of calcium and strontium in Siberian spruce (Picea obovata Ledeb.) and Siberian fir (Abies sibirica Ledeb.) tree-rings and its dependence on these woody species cell structure. Calcium concentration was found to decrease gradually from earlywood to latewood, whereas strontium showed an opposite trend. However, their trends at the scale of several rings are co-directed in the samples analyzed. A strong linear relationship was identified between the distribution of Sr/Ca concentration ratio and tree-ring density profile for both woody species. Radiographic density of Siberian spruce tree-ring cell walls and Ca and Sr concentrations in them were determined to have negative correlation with cell wall thickness. In earlywood of annual rings of a spruce the radiographic density of cell wall reaches 2.0g/cm3 and decreases to 1.2g/cm3 in latewood. The hypothesis put forward in this study to explain these strontium and calcium distributions in the tree-rings is that the concentrations of the element ions change with development of different cell wall layers. The high value of radiographic density of a cellular wall in earlywood and its relationship with cell wall thickness can be explained by the presence of ions of calcium in a cellular wall. Ions of calcium absorb X-ray radiation more strongly in comparison with light chemical elements. It can become the reason of observable relationship between radiographic density of cell wall and cell wall thickness.

The authors have investigated the image analysis system. The developed methods and software adapted for mass measurements with subsequent processing of Coniferae annular rings cellular structure histometric parameters for different modes of work.

Influence of growth conditions to the wood structure was researched on three species of conifers from various topoecological conditions in forest-steppe zone of Khakassia. By correlation analysis of climatic factors (average temperatures and precipitation amounts on ten-day periods) of growth seasons and structure parameters of wood rings (tree ring width, maximum density, radial size of tracheids and thickness of cell walls) was revealed that at different conditions of growth significant transformation of climatic signal depending on the specific features of tree species takes place. It is shown also that the main target for external signal is cambial zone; subsequent processes of cells differentiation and their result are less depending on external conditions. Nevertheless, cells parameters and particularly their combination at trees from different topoecological conditions allow to receive additional and more detailed information about climatic features of growth season and to reveal key intervals of season, when climatic factors can be evaluated quantitatively.

We analyzed tree rings in wood samples collected from some of the few surviving trees found close to the epicenter (within 4-5 km) of the Tunguska event that occurred on the last day of June 1908. Tree-ring growth shows a depression starting in the year after the event and continuing during a 4-5-year period. The most remarkable traces of the event were found in the rings' anatomical structure: (1) formation of "light" rings and a reduction of maximum density in 1908; (2) non-thickened tracheids (the cells that make up most of the wood volume) in the transition and latewood zones (the middle and last-formed parts of the ring, respectively); and (3) deformed tracheids, which are located on the 1908 annual ring outer boundary. In the majority of samples, normal earlywood and latewood tracheids were formed in all annual rings after 1908. The observed anomalies in wood anatomy suggest two main impacts of the Tunguska event on surviving trees--(1) defoliation and (2) direct mechanical stress on active xylem tissue. The mechanical stress needed to fell trees is less than the stress needed to cause the deformation of differentiating tracheids observed in trees close to the epicenter. In order to resolve this apparent contradiction, work is suggested on possible topographic modification of the overpressure experienced by these trees, as is an experimental test of the effects of such stresses on precisely analogous growing trees.

Summary Mass accumulation dynamics in earlywood and latewood cell walls of larch from northern regions of Central Siberia are investigated and correlations among cell mass of different tree-ring zones, radial tracheid sizes and tree-ring width are found. A linear relationship exists between cell wall mass and radial cell size. The deviation of cell mass from the regression line (index of mass deviation) and the mean density of the respective tree-ring zone are similarly functionally dependent on the radial cell size and reflect the realization of the potential determined during the period of cell formation. There is a critical value of larch tree-ring width in relation to cell mass. For the tree-rings with width less than this critical value the difference in the mass of earlywood and latewood cells increases with decreasing tree-ring width.The cell wall mass correlates with the monthly temperatures of June and July. Under favorable growing conditions tracheids with similar mass of cell walls are formed in earlywood and latewood, while under unfavorable conditions cell wall mass accumulation in latewood is severly limited. A comparative analysis of the cell wall mass in earlywood and latewood indicates that mass accumulation is independent of the switching processes from earlywood production to the production of latewood.

Wood material for at least 12 larch trees at six sites [Larix sibirica Ldb, Larix gmelinii (Rupr.) Rupr, Larix cajanderi Mayr] near the northern timberline in Siberia was analyzed to investigate influence of climatic factor changes on tree-ring growth at high latitudes. Tree-ring cell size, maximum latewood density and ring width measured by means of image analysis and X-ray radiodensitometry and calculated latewood cell-wall thickness were used. Correlation analysis of tree-ring structure parameter chronologies with temperatures averaged over periods of 5 days (pentad) shows that early summer temperature (mean for 5–6 pentads, depending on the region, starting from the middle of June) and date of snow melt are the most important factors that define seasonal growth and tree-ring structure. Analysis of instrumental climatic data indicates that a positive trend of early summer temperature was combined with winter precipitation (October–April) increase and this combination leads to later snow melt. Based of the results of tree-ring growth modelling, it was shown that later snow melt (hence, delayed initiation of cambial activity and, as a result, decrease of wood production) explains the changes in the relationship between tree ring width and summer temperature dynamics observed after the 1960s for a large area of the Siberian Subarctic. The understanding of the role of winter precipitation in controlling ring growth, through its effect on the timing of cambial activation, suggests the possibility of using ring structure parameters to create reconstructions of past winter precipitation variations.

The causes of a reduced sensitivity of high-latitude tree growth to variations in summer temperature for recent decades 1 , 2 , compared to earlier this century, are unknown. This sensitivity change is problematic, in that relationships between tree-ring properties and temperature are widely used for reconstructing past climate. Here we report an analysis of tree-ring and climate data from the forest–tundra zone, in combination with a mechanistic model of tree-ring growth, to argue that an increasing trend of winter precipitation over the past century in many subarctic regions 3 , 4 , 5 led to delayed snow melt in these permafrost environments. As a result, the initiation of cambial activity (necessary for the formation of wood cells) has been delayed relative to the pre-1960 period in the Siberian subarctic. Since the early 1960s, less of the growth season has been during what had previously been the period of maximal growth sensitivity to temperature. This shift results not only in slower growth, but also in a reduced correlation between growth and temperature. Our results suggest that changes in winter precipitation should be considered in seeking explanations for observed changes in the timing of the ‘spring greening’ of high-latitude forests 6 , and should be taken into account in the study of the role of the Siberian subarctic forest in the global carbon cycle.