Juliya A. Kurbatova

Modeling of the carbon dioxide fluxes in European Russia peat bogs

A process-based model (Forest-DNDC) was applied to describe the possible impacts of climate change on carbon dioxide (CO2) fluxes from a peat bog in European Russia. In the first step, Forest-DNDC was tested against CO2 fluxes measured by the eddy covariance method on an oligotrophic bog in a representative region of the southern taiga (56 ◦ N3 3 ◦ E). The results of model validations show that Forest-DNDC is capable of quantifying the CO2 fluxes from the bog ecosystem. In the second step, the validated model was used to estimate how the expected future changes of the air temperature and water table depth could affect the C dynamics in the bogs. It was shown that a decrease in the water table and an increase in temperature influence significantly the CO2 exchange between our bog ecosystem and the atmosphere. Under elevated temperature and deepened water table the bog ecosystems could become a significant source of atmospheric CO2.

Partitioning of ecosystem respiration in a paludified shallow-peat spruce forest in the southern taiga of European Russia

Soil, tree stems, and ecosystem carbon dioxide fluxes were measured by chambers and eddy covariance methods in a paludified shallow-peat spruce forest in the southern taiga of European Russia (Tver region, 56 N 33 E) during the growing seasons of 2002‐2012. The site was established in 1998 as part of the EUROSIBERIAN CARBONFLUX project, an international field experiment examining atmosphere‐biosphere interaction in Siberia and European Russia. In all years the observed annual cumulative net ecosystem flux was positive (the forest was a source of carbon to the atmosphere). Soil and tree stem respiration was a significant part of the total ecosystem respiration (ER) in this paludified shallow-peat spruce forest. On average, 49% of the ER came from soil respiration. We found that the soil fluxes exhibited high seasonal variability, ranging from 0.7 to 10 mol m 2 s 1 . Generally, the soil respiration depended on the soil temperature and ground water level. In drought conditions, the soil respiration was low and did not depend on temperature. The stem respiration of spruces grew intensively in May, had permanently high values from June to the end of September, and in October it dramatically decreased. The tree stem respiration in midsummer was about 3‐5 mol m 2 s 1 for dominant trees and about 1‐2 mol m 2 s 1 for subdominant trees. The respiration of living tree stems was about 10‐20% of the ER.

Effects of climatic changes on carbon dioxide and water vapor fluxes in boreal forest ecosystems of European part of Russia

Effects of possible climatic and vegetation changes on H2O and CO2 fluxes in boreal forest ecosystems of the central part of European Russia were quantified using modeling and experimental data. The future pattern of climatic conditions for the period up to 2100 was derived using the global climatic model ECHAM5 (Roeckner et al 2003 The Atmospheric General Circulation Model ECHAM 5. PART I: Model Description, Report 349 (Hamburg: Max-Planck Institute for Meteorology) pxa0127) with the A1B emission scenario. The possible trends of future vegetation changes were obtained by reconstructions of vegetation cover and paleoclimatic conditions in the Late Pleistocene and Holocene, as provided from pollen and plant macrofossil analysis of profiles in the Central Forest State Natural Biosphere Reserve (CFSNBR). Applying the method of paleoanalogues demonstrates that increasing the mean annual temperature, even by 1–2u2009°C, could result in reducing the proportion of spruce in boreal forest stands by up to 40%. Modeling experiments, carried out using a process-based Mixfor-SVAT model, show that the expected future climatic and vegetation changes lead to a significant increase of net ecosystem exchange (NEE) and gross primary productivity (GPP) of the boreal forests. Despite the expected warming and moistening of the climate, the modeling experiments indicate a relatively weak increase of annual evapotranspiration (ET) and even a reduction of transpiration (TR) rates of forest ecosystems compared to present conditions.

Climatic conditions of the south part of Valday Hills, Russia, and their projected changes during the 21st century

Modern climate conditions and their possible future changes in the southern part of Valday Hills, Russia, were analyzed using 40-years of meteorological data observations and global model projections. It was shown that the annual, January and July temperatures in the area increased during the last 40 years by about 0.7°, 4.0°C and 0.3°C, respectively. Annual precipitation also increased by about 60 mm. Climate simulations for the period up to 2100 provided by a general circulation model ECHAM5 (MPI Hamburg, Germany) according to B1, A1B and A2 IPCC emission scenarios propose significant changes in meteorological conditions for the study area in the future. The mean annual temperature at the end of the century may rise by 2.2-3.9°C. Increase of January temperatures under different scenarios can range between 3.3 and 6.7°C. Projected increase of annual precipitation can reach 105 mm and it is mainly manifested in growth of winter values.

Radiative Entropy Production along the Paludification Gradient in the Southern Taiga

Entropy production (σ) is a measure of ecosystem and landscape stability in a changing environment. We calculated the σ in the radiation balance for a well-drained spruce forest, a paludified spruce forest, and a bog in the southern taiga of the European part of Russia using long-term meteorological data. Though radiative σ depends both on surface temperature and absorbed radiation, the radiation effect in boreal ecosystems is much more important than the temperature effect. The dynamic of the incoming solar radiation was the main driver of the diurnal, seasonal, and intra-annual courses of σ for all ecosystems; the difference in ecosystem albedo was the second most important factor, responsible for seven-eighths of the difference in σ between the bog and forest in a warm period. Despite the higher productivity and the complex structure of the well-drained forest, the dynamics and sums of σ in two forests were very similar. Summer droughts had no influence on the albedo and σ efficiency of forests, demonstrating high self-regulation of the taiga forest ecosystems. On the contrary, a decreasing water supply significantly elevated the albedo and lowered the σ in bog. Bogs, being non-steady ecosystems, demonstrate unique thermodynamic behavior, which is fluctuant and strongly dependent on the moisture supply. Paludification of territories may result in increasing instability of the energy balance and entropy production in the landscape of the southern taiga.