Methane Flux Measurements Research Articles

Diurnal Patterns of Methane Flux from a Seasonal Wetland: Mechanisms and Methodology

Methane emissions from wetlands are temporally dynamic. Few chamber-based studies have explored diurnal variation in methane flux with high temporal replication. Using an automated sampling system, we measured methane flux every 2.5 to 4 h for 205 diel cycles during three growing seasons (2013–2015) from a seasonal wetland in the Prairie Pothole Region of North America. During ponded conditions, fluxes were generally positive (i.e., methanogenesis dominant, 10.1 ± 0.8 mg m−2 h−1), had extreme range of variation (from −1 to 70 mg m−2 h−1), and were highest during late day. In contrast, during dry conditions fluxes were very low and primarily negative (i.e., oxidation dominant, −0.05 ± 0.002 mg m−2 h−1), with the highest (least negative) fluxes occurring at pre-dawn. During semi-saturated conditions, methane fluxes also were very low, oscillated between positive and negative values (i.e., balanced between methanogenesis and methane oxidation), and exhibited no diel pattern. Methane flux was positively correlated with air temperature during ponded conditions (r = 0.57) and negatively during dry conditions (r = −0.42). Multiple regression analyses showed that temperature, light and water-filled pore space explained 72% of variation in methane flux. Methane fluxes are highly temporally dynamic and follow contrasting diel patterns that are dependent on dominant microbial processes influenced by saturation state.

Eddy Covariance Measurements of Methane Flux at a Tropical Peat Forest in Sarawak, Malaysian Borneo

AbstractTropical biogenic sources are a likely cause of the recent increase in global atmospheric methane concentration. To improve our understanding of tropical methane sources, we used the eddy covariance technique to measure CH4 flux (FCH4) between a tropical peat forest ecosystem and the atmosphere in Malaysian Borneo over a 2‐month period during the wet season. Mean daily FCH4 during the measurement period, on the order of 0.024 g C‐CH4·m−2·day−1, was similar to eddy covariance FCH4 measurements from tropical rice agroecosystems and boreal fen ecosystems. A linear modeling analysis demonstrated that air temperature (Tair) was critical for modeling FCH4 before the water table breached the surface and that water table alone explained some 20% of observed FCH4 variability once standing water emerged. Future research should measure FCH4 on an annual basis from multiple tropical ecosystems to better constrain tropical biogenic methane sources.

Micrometeorological measurement of methane flux above a tropical peat swamp forest

Tropical peat swamp forest is a unique ecosystem, in which both swamp forest and peat soil have coexisted over millennia and accumulated a significant amount of soil carbon as peat. Owing to the huge soil carbon stock and high groundwater level (GWL), tropical peatlands potentially represent a significant source of methane (CH4) to the atmosphere. However, a few studies of CH4 flux by the soil chamber technique have reported that annual CH4 emissions from tropical peat swamp forest were very low as compared to mid- and high-latitude peatlands. Recently, it has been reported that some tree species growing in peat swamp forest emit CH4 from their stems. It is impossible to continuously measure ecosystem-scale CH4 flux including both soil and plant-mediated CH4 emissions by the chamber technique. Thus, we have measured net ecosystem CH4 exchange (FCH4) above a tropical peat swamp forest in Sarawak, Malaysia using the eddy covariance technique from February 2014 to July 2015 (18 months). The mean (±1 standard deviation) of half-hourly measured FCH4 was 24.0 ± 42.2 nmol m–2 s–1. Monthly mean FCH4 was always positive during the 18 months, even in the driest month with mean GWL of –30 cm. FCH4 was positively associated with GWL or soil moisture in a quadratic form. Annual FCH4 from March 2014 through February 2015 was 7.5–10.8 g C m–2 yr–1. The annual FCH4 was much higher than annual soil CH4 emissions from tropical peatlands, because the FCH4 included aboveground CH4 emissions mainly from tree stems. However, the annual FCH4 was relatively low in comparison with those measured by the eddy covariance technique in mid- and high-latitude peatlands.

METHANE EMISSIONS FROM THERMOKARST LAKES IN THE SOUTHERN TUNDRA OF WESTERN SIBERIA

Lakes are an important natural source of methane – significant greenhouse gas of the modern atmosphere. Monitoring of methane emission from lakes ofnorthern territoriesis needed to update the available estimates of CH4 emission intensity into the atmosphere and to obtain multi-year series of observations. Field measurements of diffuse methane fluxes were carried out on lakes at different stages of thermokarst process located in Yamalo-Nenets Autonomous District (Western Siberia, Russia) during summer 2016 using static chamber method. Some statistical characteristics of measured fluxes were calculated (medians vary from 0.46 to 0.93 mgC-CH4∙m ∙h ), as well as annual diffuse emissions from studied lakes, which values are determined by the area of the lake’s water surface. Daily dynamics of methane fluxes were defined and approximation of fluxes with simple model was done, major factors are temperatures of lake bottom and of the surface air layer.

Small spatial variability in methane emission measured from a wet patterned boreal bog

Abstract. We measured methane fluxes of a patterned bog situated in Siikaneva in southern Finland from six different plant community types in three growing seasons (2012–2014) using the static chamber method with chamber exposure of 35 min. A mixed-effects model was applied to quantify the effect of the controlling factors on the methane flux. The plant community types differed from each other in their water level, species composition, total leaf area (LAITOT) and leaf area of aerenchymatous plant species (LAIAER). Methane emissions ranged from −309 to 1254 mg m−2 d−1. Although methane fluxes increased with increasing peat temperature, LAITOT and LAIAER, they had no correlation with water table or with plant community type. The only exception was higher fluxes from hummocks and high lawns than from high hummocks and bare peat surfaces in 2013 and from bare peat surfaces than from high hummocks in 2014. Chamber fluxes upscaled to ecosystem level for the peak season were of the same magnitude as the fluxes measured with the eddy covariance (EC) technique. In 2012 and in August 2014 there was a good agreement between the two methods; in 2013 and in July 2014, the chamber fluxes were higher than the EC fluxes. Net fluxes to soil, indicating higher methane oxidation than production, were detected every year and in all community types. Our results underline the importance of both LAIAER and LAITOT in controlling methane fluxes and indicate the need for automatized chambers to reliably capture localized events to support the more robust EC method.

Methane and carbon dioxide fluxes in the waterlogged forests of south and middle taiga of Western Siberia

Field measurements of methane and carbon dioxide flux were carried out using portable static chambers in south (ST) and middle taiga subzones (MT) of Western Siberia (WS) from 16 to 24 August 2015. Two sites were investigated: Bakchar bog in the Tomsk region (in typical ecosystems for this area: oligotrophic bog/forest border and waterlogged forest) and Shapsha in Khanty-Mansiysk region (in waterlogged forest). The highest values of methane fluxes (mgC·m-2·h-1) were obtained in burnt wet birch forest (median 6.96; first quartile 3.12; third quartile 8.95). The lowest values of methane fluxes (among the sites mentioned above) were obtained in seasonally waterlogged forests (median -0.08; first and third quartiles are -0.14 and -0.03 mgC·m-2·h-1 respectively). These data will help to estimate the regional methane flux from the waterlogged and periodically flooded forests and to improve its prediction.

Stover retention rather than no-till decreases the global warming potential of rainfed continuous maize cropland

During the past two decades, conservation management practices to sequester soil carbon have been recommended to mitigate greenhouse gas (GHG) emissions. However, the long-term effects of no-till, stover retention, and their interaction on soil organic carbon (SOC) stocks and GHG emissions from rainfed croplands remain uncertain. In this study, tillage practice and stover management effects were investigated in a long-term rainfed continuous maize cropping system. Measurements of soil nitrous oxide (N2O) and methane (CH4) fluxes and SOC change were conducted in four treatments: conventional tillage with stover removal (CT), conventional tillage with stover retention (CS), no tillage with stover removal (NT) and no tillage with stover retention (NS). Annual N2O emissions with stover retention (CS and NS, 0.52–0.74 kg N ha−1 yr−1) were significantly higher (P < 0.0001) than those with stover removal (CT and NT, 0.40–0.55 kg N ha−1 yr−1), but N2O emissions were not affected by tillage practice. Net CH4 consumption occurred in all treatments, but no significant effect of tillage practice or stover management was found. Surface (0–20 cm) SOC stocks decreased with both stover removal and no tillage practice, while deep SOC (20–100 cm) was not affected by tillage practice or stover management over ten years. Stover retention led to a net GHG sink with annual global warming potential (GWP) values of −2.52 ± 0.05 and −1.03 ± 0.02 Mg CO2-eq. ha−1 yr−1 for CS and NS, respectively, but stover removal practices were a net GHG source with annual GWP values of 0.83 ± 0.04 and 1.40 ± 0.04 Mg CO2-eq. ha−1 yr−1 for CT and NT, respectively. Our results highlight the importance of C input from crop residues for increasing SOC stocks and mitigating GHG emissions. Therefore, conventional tillage with crop residue return is the most promising management system for simultaneously achieving maximum yield and minimum GWP.

The development and trial of an unmanned aerial system for the measurement of methane flux from landfill and greenhouse gas emission hotspots

This paper describes the development of a new sampling and measurement method to infer methane flux using proxy measurements of CO2 concentration and wind data recorded by Unmanned Aerial Systems (UAS). The flux method described and trialed here is appropriate to the spatial scale of landfill sites and analogous greenhouse gas emission hotspots, making it an important new method for low-cost and rapid case study quantification of fluxes from currently uncertain (but highly important) greenhouse gas sources.We present a case study using these UAS-based measurements to derive instantaneous methane fluxes from a test landfill site in the north of England using a mass balance model tailored for UAS sampling and co-emitted CO2 concentration as a methane-emission proxy. Methane flux (and flux uncertainty) during two trials on 27 November 2014 and 5 March 2015, were found to be 0.140 kg s−1 (±61% at 1σ), and 0.050 kg s−1 (±54% at 1σ), respectively. Uncertainty contributing to the flux was dominated by ambient variability in the background (inflow) concentration (>40%) and wind speed (>10%); with instrumental error contributing only ∼1–2%. The approach described represents an important advance concerning the challenging problem of greenhouse gas hotspot flux calculation, and offers transferability to a wide range of analogous environments. This new measurement solution could add to a toolkit of approaches to better validate source-specific greenhouse emissions inventories – an important new requirement of the UNFCCC COP21 (Paris) climate change agreement.

Comparisons of Airborne Measurements and Inventory Estimates of Methane Emissions in the Alberta Upstream Oil and Gas Sector.

Airborne measurements of methane emissions from oil and gas infrastructure were completed over two regions of Alberta, Canada. These top-down measurements were directly compared with region-specific bottom-up inventories that utilized current industry-reported flaring and venting volumes (reported data) and quantitative estimates of unreported venting and fugitive sources. For the 50 × 50 km measurement region near Red Deer, characterized by natural gas and light oil production, measured methane fluxes were more than 17 times greater than that derived from directly reported data but consistent with our region-specific bottom-up inventory-based estimate. For the 60 × 60 km measurement region near Lloydminster, characterized by significant cold heavy oil production with sand (CHOPS), airborne measured methane fluxes were five times greater than directly reported emissions from venting and flaring and four times greater than our region-specific bottom up inventory-based estimate. Extended across Alberta, our results suggest that reported venting emissions in Alberta should be 2.5 ± 0.5 times higher, and total methane emissions from the upstream oil and gas sector (excluding mined oil sands) are likely at least 25-50% greater than current government estimates. Successful mitigation efforts in the Red Deer region will need to focus on the >90% of methane emissions currently unmeasured or unreported.

Variability in methane emissions from West Siberia's shallow boreal lakes on a regional scale and its environmental controls

Abstract. Small lakes represent an important source of atmospheric CH4 from northern wetlands. However, spatiotemporal variations in flux magnitudes and the lack of knowledge about their main environmental controls contribute large uncertainty into the global CH4 budget. In this study, we measured methane fluxes from small lakes using chambers and bubble traps. Field investigations were carried out in July–August 2014 within the West Siberian middle and southern taiga zones. The average and median of measured methane chamber fluxes were 0.32 and 0.30 mgCH4 m−2 h−1 for middle taiga lakes and 8.6 and 4.1 mgCH4 m−2 h−1 for southern taiga lakes, respectively. Pronounced flux variability was found during measurements on individual lakes, between individual lakes and between zones. To analyze these differences and the influences of environmental controls, we developed a new dynamic process-based model. It shows good performance with emission rates from the southern taiga lakes and poor performance for individual lakes in the middle taiga region. The model shows that, in addition to well-known controls such as temperature, pH and lake depth, there are significant variations in the maximal methane production potential between these climatic zones. In addition, the model shows that variations in gas-filled pore space in lake sediments are capable of controlling the total methane emissions from individual lakes. The CH4 emissions exhibited distinct zonal differences not only in absolute values but also in their probability density functions: the middle taiga lake fluxes were best described by a lognormal distribution while the southern taiga lakes followed a power-law distribution. The latter suggests applicability of self-organized criticality theory for methane emissions from the southern taiga zone, which could help to explain the strong variability within individual lakes.

Hydrocarbon seeps in Romania: Gas origin and release to the atmosphere

Romania is one of the countries with the largest number of surface hydrocarbon seeps in the world. Seeps may be an important tool for petroleum exploration as they can provide useful information regarding source rock maturity, reservoir quality, and secondary gas alterations. Seeps also represent an important source of methane, ethane, and propane to the atmosphere. To date, the genetic characterization of natural gas in Romania has only been based on molecular composition, without isotopic information. Here, we present an overview of investigations performed over the past 15 years for the main Romanian hydrocarbon seeps, and report the molecular and isotopic compositions of gas, and the fluxes of methane, ethane and propane to the atmosphere. We assessed gas origin and secondary alterations in 17 seeps from several Romanian petroleum systems, and potential source rock types and maturity have been evaluated. As previously inferred, gas within the Transylvanian Basin is largely microbial, but also displays indications of a minor thermogenic component that is likely related to a deep petroleum system. Carpathian Flysch and Foredeep petroleum systems contain thermogenic gas, with clear evidence of biodegradation in some cases. Thermogenic gas generation modelling and maturity plots suggest that most Romanian gases originate from mature type II and III kerogen (%Ro: 2–3). For cases of high flux seeps, gas has the same hydrocarbon molecular composition as the reservoir, while in weaker seeps and some mud volcanoes gas is altered by molecular fractionation (a loss of C2 and C3 during gas migration). Gas seep geochemistry, in general, reflects the different geological and maturity conditions of basins where seeps are located. A vertical sequence of petroleum systems has been suggested in some basins by seeps displaying different maturity and secondary alterations. Measurements of methane flux to the atmosphere from 94 seeps display a wide range of emissions (kilograms to hundreds of tons per year), with a total, conservative estimated methane emission of approximately 3000 t y−1. Microseepage may also release a similar quantity of methane. Consequently, seepage is a substantial contributor to natural emissions of methane on a national level.

Hydrothermal methane fluxes from the soil at Lakki plain (Nisyros Island, Greece)

Methane and CO2 flux measurements from the soils were made with the accumulation chamber method in Lakki plain covering an area of about 0.06 km2 including the main fumarolic areas of Kaminakia, Stefanos and Phlegeton. Flux values measured at 77 sites range from –3.4 to 1420 mg m-2 d-1 for CH4 and from 0.1 to 383 g m-2 d-1 for CO2. The three fumarolic areas show very different methane degassing patterns, Kaminakia showing the highest flux values. Methane output can be estimated in about 0.01 t a-1 from an area of about 2500 m2 at Phlegeton, about 0.1 t a-1 from an area of about 20,000 m2 at Stefanos and about 0.25 t a-1 from an area of about 30,000 m2 at Kaminakia. The total output from the entire geothermal system of Nisyros should not exceed 1 t a-1. Previous estimates of the CH4 output at Nisyros, based on soil CO2 output and CH4/CO2 ratios in fumarolic gases, were more than one order of magnitude higher. The present work further underscores the utmost importance of direct CH4 flux data.

Large compositional differences in the gases released from the Kizildag ophiolitic body (Turkey): Evidences of prevailingly abiogenic origin

We investigated the geochemical features of the gases released from the Kizildag ophiolitic complex (Hatay, Turkey). Twenty-three samples both dissolved in hyperalkaline waters and free gases (bubbling gases and dry seeps) were collected. Samples were analysed for their chemical (He, H2, O2, N2, CH4 and CO2) and isotopic (He, δ13C-CH4, δ2H-CH4, δ2H-H2) composition including the content and C-isotopic composition of C2 to C5 alkanes in free gases. Analytical results evidence H2 production through low-temperature (<80 °C) serpentinization processes and subsequent abiogenic CH4 production through Fischer-Tropsch-type reactions. In some sample small additions of methane either of microbial or of thermogenic origin can be hypothesized. At one of the sites (Kisecik) a clear fractionation pattern due to microbial methane oxidation leading to strongly enriched isotopic values (δ13C +15‰ and δ2H −68‰) and depletion in methane concentrations has been evidenced. At the dry gas seep of Kurtbagi methane flux measurements have been made and a preliminary output estimation of about 1000 kg per year has been obtained.

Thesis of N.A. Shnyrev: II. Principal notes

Настоящая работа посвящена разбору на наш взгляд ошибочного метода определения удельного потока метана из болот, предложенному в диссертации Николая Андреевича Шнырева «Режимные наблюдения и оценка газообмена на границе почвы и атмосферы (на примере потоков метана болотного стационара среднетаежной зоны Западной Сибири “Мухрино”)». Ошибочность предложенного метода заключается в первую очередь в том, что он является некорректным с математической точки зрения. Некорректность является достаточно часто встречающимся свойством решаемых в естественных науках задач. Основной характеристикой таких задач является то, что неизбежно возникающие при измерениях параметров задачи погрешности приводят к существенно отличающимся от реальных результатам. Для иллюстрации этого проводится численный эксперимент, показывающий, что вычисленный с помощью предложенного Н.А. Шнырёвым метода удельный поток имеет противоположный знак и оказывается в три раза больше по модулю, чем удельный поток, исходно заданный в модельном эксперименте. Кроме того, предложенный метод не учитывает нелинейный характер коэффициента диффузии газа по профилю почвы. Аналогичный метод определения потоков в холодное время года по профилю концентрации метана в снеге также страдает рядом недостатков и приводит к разным результатам в зависимости от вида использованной модели переноса газа в снежной толще. Помимо анализа работы профильного метода, обращено внимание на некоторые не соответствующие критериям научной этики заимствования, ошибочную трактовку процесса фотоокисления метана в камере при измерениях, а также ряд других вопросов.

Methane and carbon dioxide fluxes of a temperate mire in Central Europe

Observational data on greenhouse gases exchange between ecosystems and the atmosphere are crucial in understanding the global climate mechanisms. Among different methods of estimation of this exchange, the eddy-covariance (EC) technique provides a direct measure of the net flux density across the atmosphere-ecosystem interface. Still, such data are highly scarce for Central European wetlands. In this work, we present the results of two years (2013–2014) of continuous open-path EC measurements of methane (CH4) and carbon dioxide (CO2) fluxes at the wetlands of the Biebrza National Park in northeastern Poland – one of the biggest coherent lowland wetland area in Central Europe. The measurement site (53°35′30.8″N, 22°53′32.4″E) was located near the Kopytkówka river in a fen peatland, whose soils are slightly decomposed due to dehydration. The mean annual sum of CH4 release equaled 29±4gCH4m−2yr−1 in wetter year 2013 and 20±1gCH4m−2yr−1 in drier year 2014. The mean annual uptake of CO2 reached 980±150gCO2m−2yr−1 and 560±130gCO2m−2yr−1 in 2013 and 2014, respectively. Both fluxes show a clear annual pattern with maximum CH4 release in June and July (at a level of 130nmolm−2s−1) and maximum CO2 uptake in June (at a level of 4.2μmolm−2s−1). The considerable C–CO2 uptake in comparison to C–CH4 emissions suggests that the Biebrza river wetlands are a significant carbon sink, but the net contribution of the Biebrza mires to the climate forcing is unclear because of different metrics which can be used to specify the relative weights of CO2 and CH4.

Diffusive methane fluxes from Negro, Solimões and Madeira rivers and fringing lakes in the Amazon basin

AbstractThe first extensive set of measurements of methane concentrations and fluxes for the Negro River and its major tributaries combined with complementary data for the Solimões and Madeira rivers and several tributaries are presented and their temporal and spatial variations examined. Fluxes were measured using floating chambers, and dissolved CH4 concentrations were measured by the headspace technique. In the Solimões basin, tributaries had higher fluxes when water levels were low; no statistical difference among periods for lakes and the main stem river was observed. In the Negro basin, rivers had higher fluxes with greater variations among rivers during high water than during low water based on fluxes calculated from the concentration gradient and modelled gas transfer coefficients. We estimate a regional methane emission of 0.31 Tg C yr−1 for large river channels in the lowland Amazon basin.

Eddy covariance measurements of the net turbulent methane flux in the city centre – results of 2-year campaign in Łódź, Poland

Abstract. To investigate temporal variability of methane (CH4) fluxes in an urban environment, air–surface exchange fluxes of CH4 were continuously measured using eddy covariance techniques at a city-centre site in Łódź, Poland, from July 2013 to August 2015. In the immediate vicinity of the measurement site, potential methane sources include vehicle traffic, dense sewerage infrastructure and natural gas networks. Sensible and latent heat fluxes have also been measured since 2000 and carbon dioxide fluxes since 2007 at this site. Upward CH4 fluxes dominated during the measurement period, indicating that the city centre is a net source of CH4 to the troposphere. The highest monthly fluxes were observed in winter (2.0 to 2.7 g m−2 month−1) and the lowest in summer (0.8 to 1.0 g m−2 month−1). Fluxes on working days were around 6 % higher than on weekends. The cumulative flux indicates that the city centre emitted a net quantity of nearly 18 g m−2 of CH4 in 2014. Stable values of the FCO2∕ FCH4 ratio in months (minimum 2.41 × 10−3, maximum 5.3 × 10−3) and the lack of a clear annual course suggest comparable magnitude of both fluxes.

A scalable model for methane consumption in arctic mineral soils

AbstractRecent field studies have documented a surprisingly strong and consistent methane sink in arctic mineral soils, thought to be due to high‐affinity methanotrophy. However, the distinctive physiology of these methanotrophs is poorly represented in mechanistic methane models. We developed a new model, constrained by microcosm experiments, to simulate the activity of high‐affinity methanotrophs. The model was tested against soil core‐thawing experiments and field‐based measurements of methane fluxes and was compared to conventional mechanistic methane models. Our simulations show that high‐affinity methanotrophy can be an important component of the net methane flux from arctic mineral soils. Simulations without this process overestimate methane emissions. Furthermore, simulations of methane flux seasonality are improved by dynamic simulation of active microbial biomass. Because a large fraction of the Arctic is characterized by mineral soils, high‐affinity methanotrophy will likely have a strong effect on its net methane flux.

Impact of water table level on annual carbon and greenhouse gas balances of a restored peat extraction area

Abstract. Peatland restoration may provide a potential after-use option to mitigate the negative climate impact of abandoned peat extraction areas; currently, however, knowledge about restoration effects on the annual balances of carbon (C) and greenhouse gas (GHG) exchanges is still limited. The aim of this study was to investigate the impact of contrasting mean water table levels (WTLs) on the annual C and GHG balances of restoration treatments with high (ResH) and low (ResL) WTL relative to an unrestored bare peat (BP) site. Measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were conducted over a full year using the closed chamber method and complemented by measurements of abiotic controls and vegetation cover. Three years following restoration, the difference in the mean WTL resulted in higher bryophyte and lower vascular plant cover in ResH relative to ResL. Consequently, greater gross primary production and autotrophic respiration associated with greater vascular plant cover were observed in ResL compared to ResH. However, the means of the measured net ecosystem CO2 exchanges (NEE) were not significantly different between ResH and ResL. Similarly, no significant differences were observed in the respective means of CH4 and N2O exchanges. In comparison to the two restored sites, greater net CO2, similar CH4 and greater N2O emissions occurred in BP. On the annual scale, ResH, ResL and BP were C sources of 111, 103 and 268 g C m−2 yr−1 and had positive GHG balances of 4.1, 3.8 and 10.2 t CO2 eq ha−1 yr−1, respectively. Thus, the different WTLs had a limited impact on the C and GHG balances in the two restored treatments 3 years following restoration. However, the C and GHG balances in ResH and ResL were considerably lower than in BP due to the large reduction in CO2 emissions. This study therefore suggests that restoration may serve as an effective method to mitigate the negative climate impacts of abandoned peat extraction areas.

Large contribution of boreal upland forest soils to a catchment‐scale CH4 balance in a wet year

AbstractUpland forest soils affect the atmospheric methane (CH4) balance, not only through the soil sink but also due to episodic high emissions in wet conditions. We measured methane fluxes and found that during a wet fall the forest soil turned from a CH4 sink into a large source for several months, while the CH4 emissions from a nearby wetland did not increase. When upscaled to the whole catchment area the contribution of forests amounted to 60% of the annual CH4 emission from the wetlands, while in a normal year the forest soil consumes 10% of the wetland emission. The period of high upland soil emission was also captured by the nearby atmospheric concentration measurement station. Since the land cover within the catchment is representative of larger regions, our findings imply that upland forests in the boreal zone constitute an important part in the global CH4 cycle not previously accounted for.