Formation of pine wood density depending on the parameters of annual ring and latitudinal zoning

The article presents the results of studies of changes in wood density depending on annual ring width and its characteristics. Density is a basic indicator for assessing operational and technical properties of wood. At the same time, density is characterized by certain variability within the same species, depending on annual ring characteristics, influenced by environmental factors, age of trees and position in the trunk. The purpose of this study is to establish the formation of density depending on annual ring width and late wood for Scots pine (Pinus sylvestris L.) wood in the central European part of Russia. Density research was made using the specimens with one annual ring by the method of buoyancy. Absolute values of the annual ring of early and late wood were measured in cores. It was found that wood density is only influenced by late wood width in the annual ring, being under strict genetic control. In the southern taiga zone correlation between density and late wood width is varying between 0.49-0.66 and it is less than in the forest-steppe zone. The correlation of density with annual ring width in the southern taiga zone is 0.5. It is less than in the forest-steppe zone (0.57-0.81).

LANDSCAPE AND ECOLOGICALLY DIFFERENTIATED RATIONAL USE OF NATURAL RESOURCES IN AGRICULTURE OF THE ANGARA-LENA MOUNTAIN PROVINCE OF EASTERN SIBERIA

The spatial distribution of biological and ecological patterns in the Angara-Lena mountain province in Eastern Siberia is characterized according to the data of agroland- scape and ecological zoning of forage lands to assess the potential, sustainable agricultural nature management and environmental protection in the region. The province occupies area of 12 451.7 thousand hectares in the southern taiga zone and covers the Angara-Lena plateau (with 800-1460 m altitudes) and the low-mountain Primorsky Ridge. Most of the province territory (about 83%) is occupied by mountain forests. The area of agricultural land is 5% of the total area (including arable lands 2.7%, hayfields 0.7%, and pastures 1.5%). Significant areas of larch, mixed, birch forests of low mountains with a grass cover of large grasses (mountain crayfish, mixed-leaved bodyak, forest geranium, northern bedstraw, bathhouse species) and cereals (Langsdorf weinwort, spreading bor, sod pike, etc.) are used for grazing. The ecological state of the landscapes is tense, and tense and heavy for thearable. Agriculture and plant growing riskiness is highlighted according to natural and climate region features, especially erosion increasing as a result of agriculture. Simultaneously, however, the richest natural resources in the province, including fodder ones, are perspective for agriculture development.

Natural reforestation effect on soil organic carbon and СО2 flux dynamics in southern taiga ecosystems with Albeluvisols

<p><strong>Introduction.</strong> Natural reforestation is the widespread trend in the modern land-use changes in the southern taiga zone at the European territory of Russia after 1990s. Its total area is more than 10 million ha. At the same time forest natural regeneration is mutual usual process in the long-term land-use changes in this part of Russia with complex history of its development during millennium. It plays crucial role in soil successions, their fertility and environmental function dynamics including bio productivity support and carbon sequestration, which is given special attention against the background of global climate change challenges in the twenty-first century. This paper presents the results of a round-the-year monitoring of soil CO<sub>2</sub> emission in comparable sites of the fallow lands chrono sequences in conditions of a representative area of the Central Forest Reserve with background wood-sorrel spruce forests which are typical for the southern taiga zone of Central Russia.</p><p><strong>Objects and methods. </strong>The dominant soil type is sandy-loam Albeluvisols (by WRB, or Orthopodzolic soil by Russia Taxonomy, or Alfisols by Soil Taxonomy, or Podzoluvisols by FAO). The studies have been done in the representative 5 sites at different age of natural reforestation: (1) Fallow meadow grassland – “0-moment”; (2) Forest-fallow birch domination stage of 10-15 year; (3) Birch domination stage of 20-30 year with young spruce participation; (4) Birch-forest stage of 50-60 year with spruce participation; (5) Spruce-forest after fallow stage of more than 100 year with birch participation. CO<sub>2</sub> fluxes seasonal and diurnal dynamics measuring were carried out in situ using a mobile gas analyzer Li-820 and soil exposure chambers with parallel measurements of air temperature, soil temperature and moisture. Also, biomass, soil organic carbon and bulk density were analyzed in their topsoil and subsoil horizons with C stock calculation.</p><p><strong>Results and discussion.</strong> Analysis of the successional dynamics of the topsoil organic carbon stock showed the maximum rate of their increasing in the first stages of natural reforestation by a thick undergrowth of birch (more than 30 g m<sup>-2</sup>∙year<sup>-1</sup>) that agrees well with the maximum intensity of the woody biomass growth in case of dominant birch forest up to 50-60 years (more than 100 g m<sup>-2</sup>∙year<sup>-1</sup>). Research revealed the maximum intensity of soil CO<sub>2</sub> emission (up to 11-12 g C-CO<sub>2</sub> m<sup>-2</sup>∙day<sup>-1</sup>) in the meadow fallow land and its gradual decreasing in process of reforestation down to values close to background ecosystems in 4-5 g C-CO<sub>2</sub> m<sup>-2</sup>∙day<sup>-1 </sup>in the last investigated succession study with wood-sorrel spruce older than 100 years, which is in good correlation with the gradual humus accumulation in topsoil due to reduced mineralization of organic compounds from dying vegetation. The seasonal and daily dynamics of soil CO<sub>2</sub> emissions are determined by soil temperature (K<sub>TS</sub> 0.77 - 0.99), air temperature (K<sub>TA</sub> 0.42 - 0.99), and soil moisture in spring and fall (K<sub>WS</sub> -0.55 - -0.98).</p><p><strong>Conclusions. </strong>Investigation of forest natural regeneration impacts on the level of soil organic carbon accumulation and CO<sub>2</sub> fluxes in the representative southern taiga ecosystems is important element of their soil environmental monitoring and management.</p>

The potential for natural forest regeneration in the southern taiga zone of Western Siberia.

Survey of clearcut areas highlighted optimal options for coniferous undergrowth reservation in various forest types de-pending on height, number and spacing. Proposals to improve tree species composition with various thinning options are based on the findings and analysis of natural stand shaping experience. The experiment results support an opportunity to shape target stands from coniferous undergrowth with its sufficient reservation during clearcut.