Summary This paper reports the range and statistical distribution of oxidation rates of atmospheric CH4 in soils found in Northern Europe in an international study, and compares them with published data for various other ecosystems. It reassesses the size, and the uncertainty in, the global terrestrial CH4 sink, and examines the effect of land‐use change and other factors on the oxidation rate. Only soils with a very high water table were sources of CH4; all others were sinks. Oxidation rates varied from 1 to nearly 200 μg CH4 m−2 h−1; annual rates for sites measured for ≥1 y were 0.1–9.1 kg CH4 ha−1 y−1, with a log‐normal distribution (log‐mean ≈ 1.6 kg CH4 ha−1 y−1). Conversion of natural soils to agriculture reduced oxidation rates by two‐thirds –‐ closely similar to results reported for other regions. N inputs also decreased oxidation rates. Full recovery of rates after these disturbances takes > 100 y. Soil bulk density, water content and gas diffusivity had major impacts on oxidation rates. Trends were similar to those derived from other published work. Increasing acidity reduced oxidation, partially but not wholly explained by poor diffusion through litter layers which did not themselves contribute to the oxidation. The effect of temperature was small, attributed to substrate limitation and low atmospheric concentration. Analysis of all available data for CH4 oxidation rates in situ showed similar log‐normal distributions to those obtained for our results, with generally little difference between different natural ecosystems, or between short‐and longer‐term studies. The overall global terrestrial sink was estimated at 29 Tg CH4 y−1, close to the current IPCC assessment, but with a much wider uncertainty range (7 to > 100 Tg CH4 y−1). Little or no information is available for many major ecosystems; these should receive high priority in future research.

Based on theories of mire development and responses to a changing climate, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the current net C-exchange in mires requires measurements of all relevant fluxes. Estimates of annual total carbon budgets in mires are still very limited. Here, we present a full carbon budget over 2 years for a boreal minerogenic oligotrophic mire in northern Sweden (64111 0 N, 19133 0 E). Data on the following fluxes were collected: land-atmosphere CO 2 exchange (continuous Eddy covariance measurements) and CH 4 exchange (static chambers during the snow free period); TOC (total organic carbon) in precipitation; loss of TOC, dissolved inorganic carbon (DIC) and CH 4 through stream water runoff (continuous discharge measurements and regular C-concentration measurements). The mire constituted a net sink of 27 AE 3.4 ( AE SD) g C m À2 yr À1 during 2004 and 20 AE 3.4 g C m À2 yr À1 during 2005. This could be partitioned into an annual surfaceatmosphere CO 2 net uptake of 55 AE 1.9 g C m À2 yr À1 during 2004 and 48 AE 1.6 g C m À2 yr À1 during 2005. The annual NEE was further separated into a net uptake season, with an uptake of 92 g C m À2 yr À1 during 2004 and 86 g C m À2 yr À1 during 2005, and a net loss season with a loss of 37 g C m À2 yr À1 during 2004 and 38 g C m À2 yr À1 during 2005. Of the annual net CO 2 -C uptake, 37% and 31% was lost through runoff (with runoff TOC4DIC ) CH 4 ) and 16% and 29% through methane emission during 2004 and 2005, respectively. This mire is still a significant C-sink, with carbon accumulation rates comparable to the long-term Holocene C-accumulation, and higher than the C-accumulation during the late Holocene in the region.

Forested histosols have been found in some cases to be major, and in other cases minor, sources of the greenhouse gas nitrous oxide (N 2 O). In order to estimate the total national or global emissions of N 2 O from histosols, scaling or mapping parameters that can separate low-and high-emitting sites are needed, and should be included in soil databases. Based on interannual measurements of N 2 O emissions from drained forested histosols in Sweden, we found a strong negative relationship between N 2 O emissions and soil CN ratios (r 2 adj 5 0.96, mean annual N 2 O emission 5 ae (Àb CN ratio) ). The same equation could be used to estimate the N 2 O emissions from Finnish and German sites based on CN ratios in published data. We envisage that the correlation between N 2 O emissions and CN ratios could be used to scale N 2 O emissions from histosols determined at sampled sites to national levels. However, at low CN ratios (i.e. below 15-20) other parameters such as climate, pH and groundwater tables increase in importance as regulating factors affecting N 2 O emissions.

Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for COz and strong emitters of C&. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn COz and N20 emissions increase while C b emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CQ, CH., and NzO) by roughly 1 t COZ equivalentslha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

, Spatio-temporal variability of lake CH4 fluxes and its influence on annual whole lake emission estimates, 2015, Limnology and Oceanography.http://dx