Soil CO2 emission is one of the most important components of the global carbon cycle. This study analyzes the seasonal dynamics of soil emission for various land cover types in the middle taiga subzone of central Siberia during five growing seasons. It is shown that, throughout a vast area covered by pine forests and their derivatives formed on sandy soils, seasonal CO2 emission values are determined primarily by the moisture conditions and only secondarily by the temperature regime and ecosystem type. The effect of the forest type is manifested only under the most favorable moisture conditions. A new approach is proposed: divide the growing season into dry and moist periods depending on the threshold soil moisture for areas with different vegetation types.

Boreal forests in Siberia cover more than 70% of the area of this region. Due to climate change these ecosystems represent a very sensitive and significant source of carbon. In the forests, the total ecosystem respiration tends to be dominated by the soil respiration, which accounts for approximately 70% of this large flux. Global models predict that the soil respiration will increase more than the total net primary productivity in response to climate warming and increasing precipitation. In consequence, the terrestrial carbon sink is expected to decline. However, for the Siberian boreal forest there is still a gap in understanding of the future response of soil emission to drought or overprecipitation conditions. In our study we estimate how various moisture conditions could change soil emission in the boreal zone. From field observation data we find optimal soil moisture conditions. The highest dependence between the soil temperature and soil emission rates has been obtained under the optimal soil moisture conditions.

The results of study of regeneration periods in pine forests after natural and anthropogenic disturbanses have been presented. It has been found that the rate of recovery depends on the type of disturbing factor. The differentiated effect of climatic factors (air temperature, amount of precipitation) on the growth rate of forests with different types of disturbances has been investigated.

While making calculations for non-steady heat-and-moisture exchange processes in building envelope constructions it is necessary to consider moisture sorption isotherms of the materials in use. Fifteen aqueous vapor sorption models have been analyzed in order to select the simplest one that represents conventional equilibrium wood moisture values in the most accurate way. Hailwood-Horrobin and Peleg modified equations with three and four empirical constants respectively are the most suitable ones for description. When selecting models for calculations in a climatically defined range of air temperature and relative humidity values, these equations might be in preference to others. The dependence of the constants in these equations on the ambient air temperature have been calculated.

In forest ecosystems, the CO2 efflux from the soil may account for 40–80 % of the total amount of released CO2. Domination carbon breath losses over productivity may change the functional role of the ecosystem and transform it from a carbon sink to source. One of the most important field of study in soil respiration research is to identify a uniform methodology for measuring CO2 fluxes from the soil surface and its standardization. In our study, we assessed the investigation of the temporal and spatial dynamics of CO2 flux from the soil surface using the method based on the dynamic closed chambers in the middle taiga forests of Central Siberia. Soil respiration measurements were carried out during the growing season from June to October 2013. The period, when the soil respiration reached to maximum development – the second half of July to the end of August 2013. The ground cover substantially affected the value of soil respiration. The smallest value observed at the site without any plant cover – pp_sand (0.11–1.24 μmol CO2 m-2 s-1), which is 8 times lower than in the forested areas. The greatest values were attended at the site with mixed forest ranged from 2.31 to 8.41 μmol CO2 m-2 s-1. An important condition to obtain reliable results is the frequency of measurements. It was found that the measurements with a frequency of 5 or more times per month does not exceed the variation coefficient of 10 %, which indicates high reliability of the obtained values

Considered are yearly increase and long-term linear trend in the carbon dioxide concentration in the atmospheric surface layer over Central Siberia from January 2006 to December 2013. The presented results are obtained in the course of the unique high-accuracy instrumental monitoring of CO 2 concentration at the ZOTTO observatory tall tower ( www.zottoproject.org ).

The majority of negative consequences caused by extreme and natural hazards are qualified as weather and climate-related emergency situations. Programs and measures developed to reduce climate risks for economics should be based on scientific background, R&D projects and ongoing monitoring. Fire has always been remained as the main natural factor devastating forest ecosystems and outlining the status and resource potential of boreal forests. Extremely drought – afflicted hot summer and dry cold winter trigger the risks and consequences of forest fires thus affecting wildlife biodiversity and forest ecosystems performance in terms of СО2 accumulation from the atmosphere. Multifunctional and sustainable forest management in extreme natural conditions should be initiated on reliable (scientifically-proven) evaluation of ecological and resource potential of the forests with economically-effective approach developed to enhance sustainability of ecosystems to fires and insect invasion.

Direct measurements of CO2 fluxes by the eddy covariance method have demonstrated that the examined middle-taiga pine forest, raised bog, true steppe, and southern tundra along the Yenisei meridian (~90° E) are carbon sinks of different capacities according to annual output. The tundra acts as a carbon sink starting from June; forest and bog, from May; and steppe, from the end of April. In transitional seasons and winter, the ecosystems are a weak source of carbon; this commences from September in the tundra, from October in the forest and bog, and from November in the steppe. The photosynthetic productivity of forest and steppe ecosystems, amounting to 480–530 g C/(m2 year), exceeds by 2–2.5 times that of bogs and tundras, 200–220 g C/(m2 year). The relationships between the heat balance structure and CO2 exchange are shown. Possible feedback of carbon exchange between the ecosystems and atmosphere as a result of climate warming in the region are assessed.

Using direct measurements of CO2 fluxes by the method of turbulent pulsations, it was shown that the studied middle-taiga pine forest, raised bog, true steppe, and southern tundra along the Yenisei meridian (approximately 90 degrees E) are stocks of carbon of different capacity in the annual output. The tundra starts to function as a stock of carbon from June; the forest and bog, from May; and the steppe, from the end of April. In the transitional seasons and winter, the ecosystems are a weak source of carbon: the tundra already in September; the forest and bog, from October; and the steppe, from November. The photosynthetic productivity of the forest and steppe ecosys- tems (480-530 g C/(m x year) exceeds 2-2.5 times the productivity ofbogs and tundras (200-220 g C/(m x year). The relationships between the thermal balance structure and CO2 exchange are shown. Possible feedbacks between the carbon exchange between the ecosystems and the atmosphere as a result of climate warming in the region are assessed.

This paper presents the results of the assessment of carbon stocks in the coarse woody debris in the prevailing forest types of the middle taiga. Carbon stocks in down coarse woody debris were estimated to total 58.2 million tonnes, 80% of which were found in dark conifer stands, 10% in deciduous forests, and 10% in pine forests and pine logging. In pine forests of the two dominant groups of forest types and pine logging, carbon stocks amounted to 1.5– 3.3 and 1.2 million tonnes, respectively. The values obtained in this study will be used to develop a database on ecosystem components required for quantifying carbon storage and fluxes.