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The aim of current study was to develop a generic pseudo-allometric model of the biomass structure of larch (Larix spp.) trees growing in Eurasia, and to assess the impacts of temperature and precipitation. It was assumed that this model will create a prerequisite for predicting changes in the structure of the tree biomass of the genus Larix spp. under the influence of current climate shifts. According to the Trans-Eurasian hydrothermal gradients of Eurasia harvest biomass database was compiled from 510 sample trees. The data adequacy was determined by the level of variability and it accounted for 87–99% variability as the proposed by regression models. It was found that the increase in temperature by 1 °C at the constant level of precipitation causes decrease in the aboveground, stem, foliage and branches of equal-sized and equal-aged larch trees. The increase of precipitation by 100 mm at the constant level of temperature causes decrease in the aboveground and stem biomass and increase of foliage and branches.

The first attempt of modeling changes in the aboveground additive component composition of larch (genus Larix spp.) tree biomass, according to the Trans-Eurasian hydrothermal gradients of Eurasia on the database compiled for the structure of harvest biomass in a number of 510 sample trees is fulfilled. The adequacy of the obtained regularities is determined by the level of variability 87-99 % explained by the proposed regression models. For the central territory of European Russia, characterized by the mean annual temperature of January -10 °C and the mean annual precipitation of 400 mm, the increase in temperature by 1°C at the constant level of precipitation causes on Larix spp. trees of the equal age and sizes, the decrease in the aboveground, stem, needle and branches by 0.4, 0.3, 1.4 и 1.3 %, respectively. For the same region, in equal-sized trees, the increase in precipitation by 100 mm at a constant annual temperature in January causes the decrease of the aboveground and stem biomass by 1.2 and 1.7%, respectively, and the increase of needle and branches biomass by 4.0 and 6.0%, respectively. The development of such models for the main forest-forming species of Eurasia will make it possible to predict changes in the productivity of the forest cover of Eurasia in connection with climate change. Keywords: larch trees, genus Larix spp., tree biomass, allometric models

We used our database of tree biomass with a number of 433 sample trees of Larix from different ecoregions of Eurasia, involving 61 trees from Mongolia for developing an additive model of biomass tree components. Our approach solved the combined problem of additivity and regionality of the model. Our additive model of tree aboveground biomass was harmonized in two ways: first, it eliminated the internal contradictions of the component and of the total biomass equations, secondly, it took into account regional (and correspondingly species-specific) differences of trees in its component structure. A significant excess of larch biomass in the forest-tundra is found that may be explained by permafrost conditions, by tree growth in low-yielding stands with a high basic density of stem wood and relatively high developed tree crown in open stands. The aboveground biomass of larch trees in Mongolia does not stand out against the background of the most ecoregions of Eurasia. Based on our results, we conclude that the growing conditions of larch in Mongolia are not as tough as it was suggested earlier by other scientists. Biomass relations between regions may be explained by unknown and unaccounted factors and errors of measurements in all their phases (assessment of age, diameter, height of a tree, the selection of supposedly representative samples of component biomass, their drying, weighing, etc.). The question what explains the regional differences in the structure of biomass of trees with the same linear dimensions of their stems, remains open. Undoubtedly, the differences in tree age here play an important role. Also, important factor is the variation in the morphological structure of stands, which, in turn, is determined by both climatic and edaphic factors. The obtained models allow the determination of larch forest biomass in different ecoregions of Eurasia with the help of height and diameter data.

Climate change, especially modified courses of temperature and precipitation, has a significant impact on forest functioning and productivity. Moreover, some alterations in tree biomass allocation (e.g. root to shoot ratio, foliage to wood parts) might be expected in these changing ecological conditions. Therefore, we attempted to model fir stand biomass (t ha−1) along the trans-Eurasian hydrothermal gradients using the data from 272 forest stands. The model outputs suggested that all biomass components, except for the crown mass, change in a common pattern, but in different ratios. Specifically, in the range of mean January temperature and precipitation of −30°C to +10°C and 300 to 900 mm, fir stand biomass increases with both increasing temperature and precipitation. Under an assumed increase of January temperature by 1°C, biomass of roots and of all components of the aboveground biomass of fir stands increased (under the assumption that the precipitation level did not change). Similarly, an assumed increase in precipitation by 100 mm resulted in the increased biomass of roots and of all aboveground components. We conclude that fir seems to be a perspective taxon from the point of its productive properties in the ongoing process of climate change.

Since ancient times, climate change has largely determined the fate of human civilisation, which was related mainly to changes in the structure and habitats of forest cover. In the context of current climate change, one must know the capabilities of forests to stabilise the climate by increasing biomass and carbon-depositing abilities. For this purpose, the authors compiled a database of harvest biomass (t/ha) in 900 spruce (Picea spp.) sample plots in the Eurasian area and used the methodology of multivariate regression analysis. The first attempt at modelling changes in the biomass additive component composition has been completed, according to the Trans-Eurasian hydrothermal gradients. It is found that the biomass of all components increases with the increase in the mean January temperature, regardless of mean annual precipitation. In warm zonal belts with increasing precipitation, the biomass of most of the components increases. In the process of transitioning from a warm zone to a cold one, the dependence of all biomass components upon precipitation is levelled, and at a mean January temperature of ˗30°C it becomes a weak negative trend. With an increase in temperature of 1°C in different ecoregions characterised by different values of temperature and precipitation, there is a general pattern of decrease in all biomass components. With an increase in precipitation of 100 mm in different ecoregions characterised by different values of temperature and precipitation, most of the components of biomass increase in warm zonal belts, and decrease in cold ones. The development of such models for the main forest-forming species of Eurasia will make it possible to predict changes in the productivity of the forest cover of Eurasia due to climate change.

Based on a generated database of 413 sample plots, with definitions of stand biomass of the genus Populus spp. in Eurasia, from France to Japan and southern China, statistically significant changes in the structure of forest stand biomass were found, with shifts in winter temperatures and average annual precipitation. When analyzing the reaction of the structure of the biomass of the genus Populus to temperature and precipitation in their transcontinental gradients, a clearly expressed positive relationship of all components of the biomass with the temperature in January is visible. Their relationship with precipitation is less clear, in warm climate zones, when precipitation increases, the biomass of all wood components decreases intensively, and in cold climate zones, this decrease is less pronounced. The foliage biomass does not increase when precipitation decreases, as is typical for wood components, but decreases. This can be explained by the specifics of the functioning of the assimilation apparatus, namely its transpiration activity when warming, and the corresponding increase in transpiration, which requires an increase in the influx of assimilates into the foliage, and the desiccation of the climate that reduces this influx of assimilates. Comparison of the obtained patterns with previously published results for other species from Eurasia showed partial or complete discrepancies, the causes of which require special physiological studies. The results obtained can be useful in the management of biosphere functions of forests, which is important in the implementation of climate stabilization measures, as well as in the validation of the results of simulation experiments to assess the carbon-deposition capacity of forests.

In recent years, as the ecological role of forests has grown to a global level, the need to analyze their biological productivity in terms of biogeography has increased. Such studies are carried out mainly on a regional scale at the levels of both single-trees and forest stands. Thanks to formed by the authors the database on the biomass of 1076 sample trees of the genus Betula sp. growing on the territory of Eurasia, the trans-Eurasian model of tree biomass is proposed for the first time. The model takes into account regional differences in the biomass structure of equal-sized trees, harmonized on the principle of additivity.

In the gradient of pollution from the Karabash copper smelter in the Southern Urals (55° 29’ N, 60° 13’ E) in predominantly pure Scots pine and white birch stands, 12 and 34 sample plots are established, respectively, on which 42 and 56 model trees are taken, respectively, by stem diameter. The pollution gradient is expressed by the toxicity index suggested with a relative index of the content in the litter of three "technogenic" metals Cu, Pb и Fe. Regression analysis of the dependence of biomass and NPP of trees and stands from toxicity index is performed. There is a log-log-linear pattern of reduction of biomass and annual NPP of spruce-fir forest stands with increasing toxicity index in the direction to the source of pollution, but for the biomass of trees in the same gradient no consistent pattern is detected. The dry matter content (DMC) in all biomass components depends on the toxicity index and species at a statistically significant level: due to the increase in the toxicity index, it decreases in wood and bark, and increases in foliage and branches. At the same toxicity index, DMC in the branches and stem wood more in birch, but in the bark and foliage – in pine. In the wood and bark of a stem, this index is also related to the position in a stem: in the wood it decreases, and in the bark it increases in the direction from the bottom up

When using the unique in terms of the volume of database on the level of stand of the genus Quercus, the trans-Eurasian additive allometric models of biomass of stands for Eurasian Quercus forests are developed for the first time, and thereby the combined problem of model additivity and generality is solved. The additive model of forest biomass of Quercus is harmonized in two ways: it eliminated the internal contradictions of the component and the total biomass equations, and in addition, it takes into account regional differences of forest stands not only on total, aboveground and underground biomass, but also on its component structure, i.e. it reflects the regional peculiarities of the component structure of biomass.

The analysis of the biomass of oak (genus Quercus spp.) trees on the aboveground component composition based on regression equations having the additive biomass structure is fulfilled. Two trends of changes in the tree biomass structure are revealed: due to the mean January temperature and due to the mean annual precipitation. It was shown for the first time that both trends are mutually determined: the intensity of biomass trend in relation to the temperature is changing when depending on the level of precipitation, and the intensity of biomass trend in relation to precipitation level is changing during to a transition from the cold zone to the warm one and vice versa.

When using the unique in terms of the volumes of database on the level of a stand of the genus Larix Mill., the trans-Eurasian additive allometric models of biomass for Eurasian larch forests are developed for the first time, and thereby the combined problem of model additivity and generality is solved. The additive model of forest biomass of Larix is harmonized in two levels, one of which provides the principle of additivity of biomass components, and the second one is associated with the introduction of dummy independent variables localizing model for eco-regions of Eurasia. Comparative analysis of the biomass structure of larch stands of different ecoregions at the age of 100 years shows, that the greatest values of biomass (210-450 t/ha) correspond to the regions adjacent to the Atlantic and Pacific coasts, as well as to the regions, located at the southern limit of larch growing area and the lowest – to northern taiga regions of Siberia, where larch grows on permafrost. The biomass indices of different ecoregions differed not only in absolute value but also in biomass ratios of different components; for example, the proportion of needles in the aboveground biomass is maximum (5.0-7.3%) in the northern taiga of Central Siberia and the Far East on permafrost and is minimum (1.4-1.9%) in larch forests of upper productivity having biomass values 210-450 t/ha. The proposed model and corresponding tables for estimating stand biomass makes them possible to calculate larch stand biomass on Eurasian forests when using measuring taxation.

On the basis of the compiled database in a number of 3020 sample plots with determinations of forest biomass of two-needled pines (subgenus Pinus ) on theterritory ofEurasia fromGreat Britain to southernChina andJapan statistically significant transcontinental gradients of stem, roots, aboveground and total biomass are established. In the direction from North to South these biomass components change according to a bell-shaped curvewith a maximum in the third (the southern temperate) zonal belt, while the biomass of needles, branches and understory is monotonically increasing within this zonal gradient from subarctic to subequatorial zonal belts. In the direction from the Atlantic and Pacific coasts to the continentality pole inSiberia there is a biomass decrease as of all components of the wood story and the understory. The root: shoot ratio increases in the range between subarctic and southern temperate zone from 12 to 22% and then decreases to 16% in the subtropical zone, and within the southern temperate zone it monotonically increases from 20% on the oceanic coasts to 23% near continentality pole. The ratio of understory biomass to wood story biomass reduced from 4.0 to 2.5% ranging from subarctic to southern temperate zone and then rises to 3.5% in the subtropical zone, and within the south temperate zone it monotonically decreasing from the maximum value of 22% near Atlantic and Pacific coasts, approaching the level of 2-3% near the continentality pole. The results can be useful in the management of biosphere functions of forests undoubtedly.

This paper reports on measured carbon stocks in the forests of two treeline ecotones of the Ural region where climate change might improve growing conditions. The first is an alpine ecotone that is represented by an altitudinal gradient of the spruce-dominated forests on the Western slope of the Tylaiskii Kamen Mountain (Western part of the Konzhakovskii-Tylaiskii-Serebryanskii Mountain system, 59 0 30'N, 59 0 00'E), at the alpine timber line that has risen from 864 to 960 m above sea level in the course of the last 100 years. The second is an arctic ecotone in larch-dominated forests at the lower course of the Pur River (67 0 N, 78 0 E), at the transition zone between closed floodplain forests and open or island-like communities of upland forests on tundra permafrost. According to our results, there are large differences in the carbon of the aboveground biomass of both ecotones across environmental gradients. In the alpine treeline ecotone, a 19-fold drop of the carbon stocks was detected between the lower and higher altitudinal levels. In the arctic ecotone the aboveground biomass carbon stock of forests of similar densities (1300 to 1700 trees per ha) was 7 times as much in the river flood bed, and 5 times as much in mature, dense forests as the low density forests at higher elevations.

This paper presents the results of the statistical analysis of biomass and NPP estimates from vast forest areas in relation to climatic conditions. The analysis was based on biomass data in 1236 sample plots as well as both NPP and biomass estimates in 480 sample plots that were established in mixed spruce and fir stands. Data were available for the entire Eurasian territory from the UK to South China and Japan, and included information on both total biomass and various biomass components. The climatic conditions of the sampled forests were characterized by using specific indices of zonality and continentality. A system of recursive equations was fitted to the data using standard regression analysis. For both the aboveground and total NPP, we found a statistically significant increase from the North to the South, but also a decrease from both the Atlantic and Pacific coasts towards the continental center of Siberia. We also found that lower upper-story NPP is compensated by higher understory NPP and vice versa. On the other hand, inconsistencies were identified concerning the share of root biomass in relation to the continentality index.