Variation In Methane Emissions Research Articles

High-Time Resolution Analysis of Diel Variation in Methane Emission from Flooded Rice Fields

Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4 emission and to estimate the best time of day for optimum extrapolation of daily CH4 emission. Our results showed distinct diel variation in CH4 emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4 emitted per day (110–160 mg CH4 m−2 d−1) was released at 14:00–15:00. The diel pattern of CH4 emission resembled that of air temperature (Ta). The Ta coupled with solar radiation could cause a difference in partial pressure of CH4 (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4 emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4 emission is an important mechanism causing diel variation. Present address of Seok-In Yun, Department of Bio-Environmental Chemistry, Wonkwang University, 460 Iksandae-ro, Iksan, Jeonbuk 570-749, Korea.

Variability of methane emissions from an old landfill over different time‐scales

Methane (CH4) emission patterns were investigated at an old landfill in northern Germany during a 2‐year campaign over three different time‐scales (seasonal, daily and diurnal) using modified static chambers. Emissions were not uniformly distributed over the cover soil, but occurred through localized preferential pathways (hotspots). The range of emissions from the 14 investigated hotspots at any one measurement event was large, reflecting large spatial variability of emissions from the landfill. In addition, the individual hotspots showed a large temporal variability of emissions (0–9.7 mol CH4 day−1 over a range of 20 months). Environmental variables effectively modified either the biological process of methane oxidation in the soil (temperature) or the physical gas transport process (moisture and atmospheric pressure). During the seasonal campaign, emissions generally were greater in winter (moister and cooler) and smaller during the summer period (dryer and warmer). Under dry conditions, emissions were independent of soil moisture but correlated negatively with soil temperature. A positive correlation of emissions with moisture was found for moisture levels relating to a matric potential of −30 to −6 kPa, reflecting impeded diffusive oxygen ingress and hence reduced methanotrophic activity. Under very moist conditions, more than −6 kPa, emissions were negatively correlated with moisture content because of decreased gas permeability in the soil. In addition, a pressure decrease preceding the measurement was at all time‐scales often related to large emissions, whereas constant or rising pressure prior to measurement resulted in small emissions. The particular importance of the different effects depends on the type of gas transport at the specific emission location and whether it is advective or diffusive gas transport or a mixture of both, and varies at the temporal scale both between and within locations.

Inter-Annual Variations of Methane Emission from an Open Fen on the Qinghai-Tibetan Plateau: A Three-Year Study

The study aimed to understand the inter-annual variations of methane (CH4) emissions from an open fen on the Qinghai-Tibetan Plateau (QTP) from 2005 to 2007. The weighted mean CH4 emission rate was 8.37±11.32 mg CH4 m−2 h−1 during the summers from 2005 to 2007, falling in the range of CH4 fluxes reported by other studies, with significant inter-annual and spatial variations. The CH4 emissions of the year of 2006 (2.11±3.48 mg CH4 m−2 h−1) were 82% lower than the mean value of the years 2005 and 2007 (13.91±17.80 mg CH4 m−2 h−1 and 9.44±14.32 mg CH4 m−2 h−1, respectively), responding to the inter-annual changes of standing water depths during the growing season of the three years. Significant drawdown of standing water depth is believed to cause such significant reduction in CH4 emissions from wetlands in the year 2006, probably through changing the methanogen composition and decreasing its community size as well as activating methanotrophs to enhance CH4 oxidation. Our results are helpful to understand the inter-annual variations of CH4 emission and provide a more reasonable regional budget of CH4 emission from wetlands on the QTP and even for world-wide natural wetlands under climate change.

Seasonal and spatial variations of methane emissions from coastal marshes in the northern Yellow River estuary, China

Aims and methods To evaluate the seasonal and spatial variations of methane (CH4) emissions and understand the controlling factors, we measured CH4 fluxes and their environmental variables for the first time by a static chamber technique in high Suaeda salsa marsh (HSM), middle S. salsa marsh (MSM), low S. salsa marsh (LSM) and bare flat (BF) in the northern Yellow River estuary throughout a year.

Relationships between methane emissions and soil microorganisms in a double-rice field in southern subtropical China

Methane is produced in anaerobic environments by obligate anaerobic microorganisms through the decomposition of organic matters. To investigate the regression relationships between methane emissions and soil microbes in a double-rice paddy under various field practices, a two-year study was conducted to investigate the seasonal variation of methane emissions and the total activities of soil microbes (TASM) as well as the populations of methanogens (PMET) using the static closed-chamber-GC (gas chromatography) and the most probable number methods. Seven management practices were included in this study to look at the average effect of field treatments on methane emissions and TASM as well as PMET, viz. CWS (conventional tillage + without straw residues + urea), NWS (no tillage + without straw residues + urea), SCU (conventional tillage + without straw residues + controlled-release urea), HN (high stubbles + no tillage + urea), HC (high stubbles + conventional tillage + urea), SN (straw cover + no tillage + urea) and SNF (straw cover + no tillage + urea + continuous flooding). The daily average values of methane emissions and TASM as well as PMET from seven treatments were used for the analysis. Regression analysis was conducted using the R statistical software. Different field practices have significant effect on methane flux and TASM and PMET and similar seasonal variations of methane flux and TASM as well as PMET were found during the rice-growing seasons. Pronounced positive correlations between methane flux and TASM, and PMET were observed. Such relationships can be well described by the exponential or quadratic polynomial models, respectively. Regression analysis indicated that PMET could explain individually at least 97% of variance of methane flux (R2 = 0.97, P < 0.001), while the fitting precision of multiple nonlinear regression model for methane flux with two predictors of TASM and PMET was slightly higher than the univariate regression analysis (R2 = 0.98, P < 0.001). However, as we know, methane emissions from paddy soils are affected by many factors, of which TASM and PMET are the most direct influential variants. In order to reasonably reveal the interactions between methane emissions and environmental factors, the multivariate nonlinear regression analysis should be carried out based on data derived from the extensive field experiments rather than few laboratory trials.

Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations

Abstract. Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr−1 (including the soil sink) and rice paddy emissions in the year 2000 were 42 Tg CH4 yr−1. Tropical wetlands contributed 201 Tg CH4 yr−1, or 78% of the global wetland flux. Northern latitude (&gt;50 N) systems contributed 12 Tg CH4 yr−1. However, sensitivity studies show a large range (150–346 Tg CH4 yr−1) in predicted global methane emissions (excluding emissions from rice paddies). The large range is sensitive to (1) the amount of methane transported through aerenchyma, (2) soil pH (±100 Tg CH4 yr−1), and (3) redox inhibition (±45 Tg CH4 yr−1). Results are sensitive to biases in the CLMCN and to errors in the satellite inundation fraction. In particular, the high latitude methane emission estimate may be biased low due to both underestimates in the high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4.

Source attribution of the changes in atmospheric methane for 2006–2008

Abstract. The recent increase of atmospheric methane is investigated by using two atmospheric inversions to quantify the distribution of sources and sinks for the 2006–2008 period, and a process-based model of methane emissions by natural wetland ecosystems. Methane emissions derived from the two inversions are consistent at a global scale: emissions are decreased in 2006 (−7 Tg) and increased in 2007 (+21 Tg) and 2008 (+18 Tg), as compared to the 1999–2006 period. The agreement on the latitudinal partition of the flux anomalies for the two inversions is fair in 2006, good in 2007, and not good in 2008. In 2007, a positive anomaly of tropical emissions is found to be the main contributor to the global emission anomalies (~60–80%) for both inversions, with a dominant share attributed to natural wetlands (~2/3), and a significant contribution from high latitudes (~25%). The wetland ecosystem model produces smaller and more balanced positive emission anomalies between the tropics and the high latitudes for 2006, 2007 and 2008, mainly due to precipitation changes during these years. At a global scale, the agreement between the ecosystem model and the inversions is good in 2008 but not satisfying in 2006 and 2007. Tropical South America and Boreal Eurasia appear to be major contributors to variations in methane emissions consistently in the inversions and the ecosystem model. Finally, changes in OH radicals during 2006–2008 are found to be less than 1% in inversions, with only a small impact on the inferred methane emissions.

Seasonal and spatial variations of methane emissions from montane wetlands in Northeast China

Abstract To evaluate the seasonal and spatial variations of CH4 emissions and understand the controlling factors, we measured CH4 fluxes and their environmental variables from seven natural wetlands in mountainous regions in northeast China using a static chamber technique during a growing season from May to October in 2008. Four sites were significant atmospheric CH4 sources, ranked in order from highest to lowest according to their seasonal mean CH4 release; these sites were a marsh (34.18 mgCH4 m−2 h−1), two deciduous forested swamps (0.83–18.21 mgCH4 m−2 h−1) and a thicket swamp (0.43 mgCH4 m−2 h−1). Coniferous forested swamps, forested fens and bogs are unique wetlands in northeast China and represent large wetland coverage in this zone, but they were observed to be weak sinks of atmospheric CH4 (−0.08 to −0.01 mgCH4 m−2 h−1). Similar seasonal variations can be observed at marsh, thicket swamp and two deciduous forested swamps sites, with peaks were observed during the summer and early autumn (July to early September). However, no seasonal pattern was found at the other three sites. Seasonal variations of CH4 fluxes were primarily affected by the soil temperature. However, spatial variation among wetlands was mainly controlled by the water table, the soil temperature, plant aboveground biomass and potential CH4 production. A high water table and herb-dominant sites had high potential CH4 production rates and thus induced high CH4 fluxes. In contrast, a low water table and tree- or moss-dominant sites had low potential CH4 production rates and induced low CH4 fluxes.

Effects of Animal and Climate Parameters on Gas Emissions from a Barn for Fattening Pigs

Increased knowledge of the factors that affect emissions from livestock barns may lead to a better understanding of daily (between different days) and diurnal (within a specific day) variations in emissions, an improvement of mitigation methods and a refinement of emission models. The influence of animal activity, animal weight, indoor air temperature and relative humidity on carbon dioxide, methane, and ammonia emissions was assessed on a daily and diurnal basis in a barn with three successive batches of fattening pigs. The floor was partly slatted, manure was removed daily, and the ventilation rate was fixed for each batch. Variations between the batches in mean methane emissions (0.33–1.62 g pig-1 h-1) were larger than the variations in the mean emissions of carbon dioxide (84–91 g pig-1 h-1) and ammonia (0.18–0.20 g pig-1 h-1). Animal weight explained most of the daily variations in carbon dioxide and ammonia emissions. Animal weight and indoor air temperature explained most of the daily variations in methane emissions. A regression analysis of methane emissions as a function of the indoor air temperature and animal weight explained 56% of the variations in the measured methane emissions. Animal activity decreased with increasing animal weight and air temperature. Diurnal variations in carbon dioxide and ammonia emissions were mainly affected by the animal activity, with correlation coefficients (r) of 0.89 and 0.68, respectively. Diurnal variations in methane emissions only slightly correlated with the animal activity (r = 0.41, p = 0.05). Emission variations emphasized the need for measurements during different times within the day and during the growing period in order to obtain reliable data for assessing abatement techniques.

Spatial–temporal variations of methane emissions from the Ertan hydroelectric reservoir in southwest China

AbstractMethane emissions from hydroelectric reservoirs can comprise a considerable portion of anthropogenic methane. However, lack of data on CH4 emissions in different geographical regions and high spatial‐temporal variability in the emission rates of reservoirs has led to uncertainties regarding regional emission estimates of CH4. In the subtropical plateau climate region, we used the Ertan hydroelectric reservoir as a study area. The CH4 flux at the air‐water interface was assessed by floating chambers and factors influencing emissions, including the distance from the dam, water depth, seasonal variation in wet and dry season, air‐water temperature gradient and wind speed, and was also studied through a year‐long systematic sampling and monitoring experiment. The results showed that the surface of the reservoir was a source of CH4 during the sampling period and the annual average CH4 flux was 2·80 ± 1·52 mg m−2 d−1. CH4 flux (and its variation) was higher in the shallow water areas than in the deep‐water areas. CH4 flux near the dam was significantly higher than that of other locations farther from the dam in the dry season. The seasonal variations of CH4 emission in wet and dry seasons were minor and significant diurnal variations were observed in wet and dry seasons. Exponential relationships between the CH4 flux and air‐water temperature gradient were found. Air‐water temperature gradient was an important factor influencing diurnal variations of CH4 flux in the Ertan hydroelectric reservoir. These results indicate that systematic sampling is needed to better estimate CH4 flux through coverage of the spatial variation of different water depths, measuring‐point distance from the dam, seasonal variation in wet and dry seasons and changes in climate factors (such as air‐water temperature gradient). Our results also provide a fundamental parameter for CH4 emission estimation of global reservoirs. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Vegetation height and other controls of spatial variability in methane emissions from the Arctic coastal tundra at Barrow, Alaska

We conducted measurements of methane (CH4) emission and ecosystem respiration on &gt;200 points across the Arctic coastal tundra near Barrow, Alaska, United States, in July 2007 and August 2008. This site contains broad diversity in tundra microtopography, including polygonal tundra, thaw lakes, and drained lake basins. In 2007, we surveyed CH4 emissions across this landscape, and found that soil water content was the strongest control of methane emission rate, such that emission rates rose exponentially with water content. However, there was considerable residual variation in CH4 emission in the wettest soils (&gt;80% volumetric water content) where CH4 emissions were highest. A statistical analysis of possible soil and plant controls on CH4 emission rates from these wet soils revealed that vegetation height (especially of Carex aquatilis) was the best predictor, with ecosystem respiration and permafrost depth as significant copredictors. To evaluate whether plant height served as a proxy for aboveground plant biomass, or gross primary production, we conducted a survey of CH4 emission rates from wet, Carex‐dominated sites in 2008, coincidently measuring these candidate predictors. Surprisingly, vegetation height remained the best predictor of CH4 emission rates, with CH4 emissions rising exponentially with vegetation height. We hypothesize that taller plants have more extensive root systems that both stimulate more methanogenesis and conduct more pore water CH4 to the atmosphere. We anticipate that the magnitude of the climate change–CH4 feedback in the Arctic Coastal Plain will strongly depend on how permafrost thaw alters the ecology of Carex aquatilis.

Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covariance

AbstractEddy covariance measurements of methane (CH4) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May–September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH4 net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH4 emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH4 emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181–215, nighttime average CH4 efflux was only 47% of the average midday values. The peak value for daily average CH4 emission rate was approximately 80 nmol m−2 s−1 (4.6 mg CH4 m−2 h−1), and seasonal variation in CH4 flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144–269 (late May–late September)], the total CH4 emission was 3.2 g CH4 m−2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO2 sequestration that was measured (18.1 mol CO2 m−2 or 217 g C m−2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH4 emission over the last 50 years.

水田からのメタン発生に関する研究(第2報)―水稲体におけるメタンの主要経路,日変化に及ぼす温度,光の影響―

水田からのメタン発生に関する研究(第2報)―水稲体におけるメタンの主要経路,日変化に及ぼす温度,光の影響―

Modeling Methane Emission from Wetlands in North-Eastern New South Wales, Australia Using Landsat ETM+

Natural wetlands constitute a major source of methane emission to the atmosphere, accounting for approximately 32 ± 9.4% of the total methane emission. Estimation of methane emission from wetlands at both local and national scale using process-based models would improve our understanding of their contribution to global methane emission. The aim of the study is to estimate the amount of methane emission from the coastal wetlands in north-eastern New South Wales (NSW), Australia, using Landsat ETM+ and to estimate emission with a temperature increase. Supervised wetland classification was performed using the Maximum Likelihood Standard algorithm. The temperature dependent factor was obtained through land surface temperature (LST) estimation algorithms. Measurements of methane fluxes from the wetlands were performed using static chamber techniques and gas chromatography. A process-based methane emission model, which included productivity factor, wetland area, methane flux, precipitation and evaporation ratio, was used to estimate the amount of methane emission from the wetlands. Geographic information system (GIS) provided the framework for analysis. The variability of methane emission from the wetlands was high, with forested wetlands found to produce the highest amount of methane, i.e., 0.0016 ± 0.00009 teragrams (Tg) in the month of June, 2001. This would increase to 0.0022 ± 0.0001 Tg in the month of June with a 1 °C rise in mean annual temperature by the year 2030 in north-eastern NSW, Australia.

A study of the dynamics behind methane emissions from northern wetlands

Methane is an important greenhouse gas, contributing 22% to the increased radiative forcing over 150 years, and emissions from wetlands are key to its global dynamics. A general model of methane dynamics is presented that emphasizes the impact of external climate factors on methane production and oxidation. The model consists of two uncoupled bacterial populations, each following a logistic growth pattern, and a third differential equation, dependent on these two populations, that represents the concentration of stored methane in wetland soils. This is related to methane emissions into the atmosphere. Several simplified models are also presented to demonstrate the development of the model from the basic processes occurring in the soil. Analysis of the model shows a stable equilibrium point for the methane concentration. This equilibrium is subject to short-term forcing by climate, specifically changes in temperature and water table depth. Parameters for this model are then fitted to real data taken from a wetland site in Teesdale, and this forcing is shown to account for much of the observed variation in methane emissions. An attempt to extend this model to longer time scales is made, by considering the average climate. This extension is shown to be unsuccessful through considering Taylor’s theorem and its implications for the model. Finally, a simplistic approximation to climate change is made, and the consequences of these changes on methane emissions predicted by the model are presented. These consequences are found to include negative feedback, where the change in climate eventually results in lower emissions of methane.

Methane emissions from newly created marshes in the drawdown area of the Three Gorges Reservoir

The study aimed to understand the methane (CH4) emission and its controlling factors in the Three Gorges Reservoir Region and to explore its implication for large dams. We measured CH4 emissions from four vegetation stands in newly created marshes in the drawdown area of the Three Gorges Reservoir, China, in the summer of 2008. The results showed highly spatial variations of methane emissions among the four stands, with the smallest emission (0.25 ± 0.65 mg CH4 m−2 h−1) in the Juncus amuricus stand, and the greatest (14.9 ± 10.9 mg CH4 m−2 h−1) in the Scirpus triqueter stand. We found that the spatial variations of CH4 emissions are caused by difference in standing water depth and dissolved organic carbon (DOC). Results also showed a special seasonal variation of CH4 emissions in this area, i.e., maximal emissions in early July followed by a low and steady value before the winter flooding. The seasonality of CH4 emissions was found closely related to temperature and standing water depth. Because of the large area of the drawdown zones for global dam reservoirs and a large CH4 emission rate, such newly created marshes should not be neglected when estimating CH4 emissions from reservoirs.

Diurnal variation of methane emissions from an alpine wetland on the eastern edge of Qinghai-Tibetan Plateau

Alpine wetland is a source for CH(4), but little is known about methane emission from such wetland, especially about its diurnal pattern. In this study we tried to probe the diurnal variation in methane emission from alpine wetland vegetation. The average methane emission rate was 9.6 +/- 3.4 mg CH(4) m(-2) h(-1). There was an apparent diurnal variation pattern in methane emission with one minor peak at 06:00 and a major one at 15:00. The sunrise peak was consistent with a two-way transport mechanism for plants (convective at daytime and diffusive at night-time). CH(4) emission was found significantly correlated with redox potentials. The afternoon peak could not be explained by diurnal variation in soil temperature, but could be attributable to changes in CH(4) oxidation and production driven by plant gas transport mechanism. The results have important implications for sampling and scaling strategies for estimating methane emission from alpine wetlands.

Spatial variations on methane emissions from Zoige alpine wetlands of Southwest China

This study was aimed to understand the spatial variation of CH 4 emissions from alpine wetlands in Southwest China on a field-scale in two phenological seasons, namely the peak growing season and the spring thaw. Methane emission rates were measured at 30 plots, which included three kinds of environmental types: dry hummock, Carex muliensis and Eleocharis valleculosa sites. There were highly spatial variations of methane emissions among and within different environmental types in both phenological seasons. Mean methane emission rates ranged from 1.1 to 37.0 mg CH 4 m − 2 h − 1 in the peak growing season and from 0.004 to 0.691 mg CH 4 m − 2 h − 1 in the spring thaw. In the peak growing season, coefficients of variation (CV) averaged 38% among environmental types and 64% within environmental types; while in the spring thaw, CV were on the average 61% among environmental types and 96% within environmental types. The key influencing factors were the standing water table and the plant community height in the peak growing season, while in the spring thaw, no significant correlations between factors and methane emissions were found.

Spatial variability of methane emissions from rice fields and implications for experimental design

It is observed that side by side plots in rice fields, managed by the same practices, produce methane emissions that are often different by factors of 2 to 4. Similarly on a given day when many plots are sampled, the emissions from one plot may differ from another by factors of 3–4 on average. These large variations must be taken into account if these data are extrapolated to larger scales such as countries or the world. In this paper we analyze and delineate the nature of this variability. We distinguish temporal and spatial variability and examine the effects of both on the observed seasonal average emission rates. While temporal variability is managed well in most experiments because frequent measurements are taken, the spatial variability remains a potential major uncertainty in many experiments. Using the characteristics of the observed variability we use simulations to show that with a proper and realistic sampling strategy, it is possible to get to within 15%–20% of the true flux for most cases of interest. We calculate how many plots are needed and how often they should be sampled during the growing season to obtain a seasonal average flux within prescribed limits relative to the true flux.

Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications

To understand the seasonality of methane flux from alpine wetlands in Zoige Plateau, 30 plots were set to measure the methane emissions in the growing and nongrowing seasons in three environmental types: dry hummock (DH), Carex muliensis (CM), and Eleocharis valleculosa (EV) sites. There were clearly seasonal patterns of methane flux in different environmental types in the growing and nongrowing seasons. Mean methane emission rate was 14.45 mg CH4 m−2 h−1 (0.17 to 86.78 mg CH4 m−2 h−1) in the growing season, and 0.556 mg CH4 m−2 h−1 (0.002 to 6.722 mg CH4 m−2 h−1) in the nongrowing season. In the growing season, the main maximum values of methane flux were found in July and August, except for a peak value in September in CM sites. In the nongrowing season, the similar seasonal variation pattern was shared among all the three sites, in which the methane emissions increased from February to April. In the growing season, the determining factors were surface temperatures (r2 = 0.55, P &lt; 0.05), standing water depths (r2 = 0.32, P &lt; 0.01) and plant community heights (r2 = 0.61, P &lt; 0.01), while in the nongrowing season, ice thickness (r2 = 0.27, P &lt; 0.05; in CM and EV sites) was found most related to flux. In our understanding, the seasonality of methane emissions in our study areas was temperature‐ and‐plant‐growth‐dependent, and the water table position was also very important to shape the temperature‐and‐plant‐growth‐dependent seasonal variation of flux with its vigorous variations in alpine wetland ecosystems. Different environmental types within the wetland also influenced the seasonal pattern of methane flux. For an accurate estimate of the global methane source strength of alpine wetlands, the pronounced seasonal or even temporal variability in methane emission from alpine wetlands should be taken into consideration.