Ecosystem carbon dioxide, energy, and water fluxes were measured using eddy covariance in a fresh clear-cut surrounded by a mixed spruce-birch-aspen forest in the boreal zone of European Russia. Measurements were initiated in spring 2016 following timber harvest and continued for five months. The influence of surrounding forest on air flow and turbulent fluxes within the clear-cut were examined using a process-based two-dimensional (2D) hydrodynamic turbulent exchange model. The clear-cut was a source of CO 2 to the atmosphere prior to onset of vegetation growth during early spring. During this period the mean daily latent (LE) and sensible (H) heat fluxes were very similar and the Bowen ratio (b = H/LE) averaged about 1.0. Daily net ecosystem exchange of CO 2 (NEE) was around 0 gC m À2 d À1 following onset of vegetation growth from mid-spring through summer, while b declined to 0.6-0.7. There was strong diurnal variability in NEE, LE and H over the measurement period that was governed by solar radiation and temperature as well as the leaf area index (LAI) of regrown vegetation. Modeled vertical CO 2 and H 2 O fluxes along a transect that crossed the clear-cut and coincided with the dominate wind direction showed that the clear-cut strongly influenced turbulent fluxes within the atmospheric surface layer. Furthermore, modeled atmospheric dynamics suggested that the clear-cut had a large influence on turbulent fluxes in the downwind forest, but little impact on the upwind side. An aggregated approach including field measurements and process-based models can be a useful approach to estimate energy, water and carbon dioxide fluxes in non-uniform forest landscapes.

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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 µmol 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 µmol m −2 s −1 for dominant trees and about 1-2 µmol m −2 s −1 for subdominant trees. The respiration of living tree stems was about 10-20% of the ER.

Abstract. Climate warming in high latitudes impacts CO2 sequestration of northern peatlands through the changes in both production and decomposition processes. The response of the net CO2 fluxes between ecosystems and the atmosphere to the climate change and weather anomalies can vary across the forest and non-forest peatlands. To better understand the differences in CO2 dynamics at forest and non-forest boreal peatlands induced by changes in environmental conditions the estimates of interannual variability of the net ecosystem exchange (NEE), total ecosystem respiration (TER) and gross primary production (GPP) was obtained at two widespread peatland ecosystems – paludified spruce forest and adjacent ombrotrophic bog in the southern taiga of west Russia using 6-year of paired eddy covariance flux measurements. The period of measurements (2015–2020) was characterized by both positive and negative annual and growing season air temperature and precipitation anomalies. Flux measurements showed that in spite of the lower growing season TER (332…339 gC∙m−2) and GPP (442…464 gC∙m−2) rates the bog had a lower NEE (−132…−108) than the forest excepting the warmest and the wettest year of the period and was a sink of atmospheric CO2 in the selected years while the forest was a CO2 sink or source between years depending on the environmental conditions. Growing season NEE at the forest site was between −142 and 28 gC∙m−2, TER between 1135 and 1366 gC∙m−2 and GPP between 1207 and 1462 gC∙m−2. Annual NEE at the forest was between −62 and 145 gC∙m−2, TER between 1429 and 1652 gC∙m−2 and GPP between 1345 and 1566 gC∙m−2 respectively. Anomalously warm winter with sparse and thin snow cover lead to the increased GPP as well as lower NEE in early spring at forest and to the increased spring TER at the bog. Also, the shifting of the compensation point to the earlier dates at the forest and to the later dates at the bog following the warmest winter of the period was detected. This study suggest that the warming in winter can increase CO2 uptake of the paludified spruce forests of southern taiga in non-growing season.

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The use of unmanned aerial vehicles for detailed mapping of ecosystems has become increasingly important in recent years. As one of the main terrestrial carbon reserves, peatland ecosystems are of the great interest in obtaining highly detailed orthophotoplans. At the same time, there is a lack of publications devoted to the total carbon dioxide fluxes in each type of bog microforms. This paper presents the results of our study, which aimed to develop methods for mapping peatland microlandscapes and for estimation of integral carbon dioxide fluxes between the peatland surface and the atmosphere. Based on a highly detailed orthophotoplan compiled using unmanned aerial vehicles, we assessed the areas of major microform groups (swamps, hollows, and ridges) in a bog located in the Central Forest State Nature Biosphere Reserve (European Russia). The classification accuracy ranged from 79% to 93%. The areas of ridges, hollows, and swamps were 0.16 km 2 , 0.32 km 2 , and 0.12 km 2 , respectively. To make an integral estimation of carbon dioxide fluxes, we used earlier data on carbon dioxide emissions (ecosystem respiration), uptake (gross ecosystem exchange), and balance (net ecosystem exchange) measured by soil chamber method on representative experimental plots of respective microform types. After recalculating fluxes to areas of microforms, the integral values for different classes in the summer seasons of 2014, 2016 and 2017 were 15-91 kg CO 2 × h-1 for ecosystem respiration, 21-190 kg CO 2 × h-1 for gross ecosystem exchange, and from-122 kg CO 2 × h-1 to 41 kg CO 2 × h-1 for net ecosystem exchange. The results of the study confirmed that highly detailed orthophotoplans, obtained with the use of unmanned aerial vehicles, make it possible to distinguish the boundaries of such bog microforms as swamps, hollows and ridges with a high accuracy, despite the presence of some errors in the classification. The study of the structural and functional organisation of the bog should be carried out with considering its seasonal and interannual dynamics as well as all microform types.

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Many studies report asymmetrical spatial distribution of soil respiration caused by presence of areas with significantly higher emission rates (so-called hot spots). For seasonally dry tropical forest soil respiration was measured on 1 ha plot with 20m, 5m and 1 m scale in the first half of dry season. 457 measurements made in 9 series at 54 sampling points. The results suggest that lognormal spatial distribution model appears to be much more supported rather than the normal one. A statistical method proposed for estimation the mean value and its confidence interval of lognormally distributed data. The mean emission rate E(R S) for the lognormal distribution amounted to 4.28 µmol m-2 s-1 , the 95% confidence interval is 3.93 to 4.76 µmol m-2 s-1. However, the standard sample mean can be used as an estimator of the mean of lognormally distributed values of soil respiration if their coefficient of variance remains approximately the same as in our study (CV=0.35). Based on the data obtained and literature sources, recommendations are given on the number of sampling points for estimating the spatial average value with a given accuracy