Methane (CH₄) production, oxidation, and emission were studied in ponds of the permafrost‐affected polygonal tundra in northeast Siberia. Microbial degradation of organic matter in water‐saturated soils is the most important source for the climate‐relevant trace gas CH₄. Although ponds and lakes cover a substantial fraction of the land surface of northern Siberia, data on CH₄ fluxes from these water bodies are scarce. Summer CH₄ fluxes were measured with closed chambers at the margins of ponds vegetated by vascular plants and in their centers without vascular plants. Furthermore, CH₄ and oxygen concentration gradients, stable carbon isotope signatures of dissolved and emitted CH₄, and microbial CH₄ production and CH₄ oxidation were determined. Mean summer fluxes were significantly higher at the margins of the ponds (46.1 ± 15.4 mg CH₄ m⁻² d⁻¹) than at the centers (5.9 ± 8.2 mg CH₄ m⁻² d⁻¹). CH₄ transport was dominated by diffusion in most open water sites, but substantial ebullitive fluxes (12.0 ± 8.1 mg CH₄ m⁻² d⁻¹) were detected in one pond. Plant‐mediated transport accounted for 70 to 90% of total CH₄ fluxes above emerged vegetation. In the absence of vascular plants, 61 to 99% of the CH₄ produced in the anoxic bottom soil was consumed in a layer of the submerged moss Scorpidium scorpioides, which covered the bottoms of the ponds. The fraction of CH₄ oxidized was lower at sites with vascular plants since CH₄ was predominantly transported through their aerenchyma, thereby bypassing the CH₄ oxidation zone in the moss layer. These results emphasize the importance of moss‐associated CH₄ oxidation causing low CH₄ fluxes from the studied Siberian ponds.

Rates of CO₂ efflux from the floor of a central Siberian Scots pine (Pinus sylvestris) forest were measured using a dynamic closed chamber system and by a eddy covariance system placed 2.5 m above the forest floor. Measurements were undertaken for a full growing season: from early May to early October 1999. Spatial variability as determined by the chamber measurements showed the rate of CO₂ efflux to depend on location, with rates from relatively open areas (“glades”) only being about 50% those observed below or around trees. This was despite generally higher temperatures in the glade during the day. A strong relationship between CO₂ efflux rate and root density was observed in early spring, suggesting that lower rates in open areas may have been attributable to fewer roots there. Continuous measurements with the eddy covariance system provided good temporal coverage. This method, however, provided estimates of ground CO₂ efflux rate rates that were about 50% lower than chamber measurements that were undertaken in areas considered to be representative of the forest as a whole. An examination of the seasonal pattern of soil CO₂ efflux rates suggests that much of the variability in CO₂ efflux rate could be accounted for by variations in soil temperature. Nevertheless, there were also some indications that the soil water deficits served to reduce soil CO₂ efflux rates during mid-summer. Overall the sensitivity of CO₂ efflux rate to temperature seems to be greater for this boreal ecosystem than has been the case for most other studies. DOI: 10.1034/j.1600-0889.2002.01348.x

The observed high spatial variation in soil respiration (SR) and associated parameters emphasized the importance of SR heterogeneity at high latitudes and the involvement of many factors in its regulation, especially within fire-affected areas. The problem of estimating CO₂ emissions during post-fire recovery in high-latitude ecosystems addresses the mutual influence of wildfires and climate change on the C cycle. Despite its importance, especially in permafrost regions because of their vulnerability, the mutual influence of these factors on CO₂ dynamics has rarely been studied. Thus, we aimed to understand the dynamics of soil respiration (SR) in wildfire-affected larch recovery successions. We analyzed 16-year data (1995–2010) on SR and associated soil, biological, and environmental parameters obtained during several field studies in larch stands of different ages (0–276 years) in the Krasnoyarsk region (Russia). We observed a high variation in SR and related parameters among the study sites. SR varied from 1.77 ± 1.18 (mean ± SD) µmol CO₂ m⁻² s⁻¹ in the 0–10-year-old group to 5.18 ± 2.70 µmol CO₂ m⁻² s⁻¹ in the 150–276-year-old group. We found a significant increasing trend in SR in the 88–141-year old group during the study period, which was related to the significant decrease in soil water content due to the shortage of precipitation during the growing season. We observed a high spatial variation in SR, which was primarily regulated by biological and environmental factors. Different parameters were the main contributors to SR in each group, an SR was significantly affected by the inter-relationships between the studied parameters. The obtained results can be incorporated into the existing SR databases, which can allow their use in the construction and validation of C transport models as well as in monitoring global fluctuations in the C cycle in response to climate change.

An analysis of CO2emissions and soil microbiological activity has been performed in larch stands of different ages that developed on cryogenic soils and represent different stages of post-fire...