Methane dynamics in the subarctic tundra: combining stable isotope analyses,  plot- and ecosystem-scale flux measurements

Marushchak, Maija E.; Friborg, Thomas; Biasi, Christina; Herbst, Mathias; Johansson, Torbjörn; Kiepe, I.; Liimatainen, Maarit; Lind, Saara E.; Martikainen, Pertti J.; Virtanen, Tarmo; Soegaard, H.; Shurpali, Narasinha J.

doi:10.5194/bg-13-597-2016

Cited by 48 publications

(58 citation statements)

References 50 publications

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“…The effect of LAI TOT on methane flux was about one-third higher than the effect of LAI AER . Previously, Marushchak et al (2016) have found a positive correlation between LAI of vascular plants and methane emissions that explained most of the differences in methane fluxes among the fens and willow stands they measured. The positive effect of LAI TOT on methane flux can be explained by the fact that it provides organic substrate for methanogenesis (Chanton et al, 1995).…”

Section: Discussionmentioning

confidence: 83%

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

et al. 2018

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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)(2013)(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 (LAI TOT ) and leaf area of aerenchymatous plant species (LAI AER ). Methane emissions ranged from −309 to 1254 mg m −2 d −1 . Although methane fluxes increased with increasing peat temperature, LAI TOT and LAI AER , 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 LAI AER and LAI TOT in controlling methane fluxes and indicate the need for automatized chambers to reliably capture localized events to support the more robust EC method.

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Section: Discussionmentioning

confidence: 83%

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

et al. 2018

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“…However, there was not a 1:1 relationship between upscaled fluxes using the footprint model and the EC towers, indicating that this methodology may underestimate the overall flux, the opposite to Budischev et al [30], who showed the footprint model method produced a slight overestimation of the flux in comparison to the EC towers, attributed to localised differences in environmental conditions across the measurement period and vegetation classification error. Maruschak et al [90] also upscaled chamber measurements aross a sub-arctic tundra ecosystem, using a high-resolution vegetation map and weighting the fluxes by their relative area. They found that this method again indicated an overestimation of the chamber measurements in comparison to the EC towers.…”

Section: Upscaled Flux Chamber Measurementsmentioning

confidence: 99%

Upscaling CH4 Fluxes Using High-Resolution Imagery in Arctic Tundra Ecosystems

et al. 2017

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Abstract:Arctic tundra ecosystems are a major source of methane (CH 4 ), the variability of which is affected by local environmental and climatic factors, such as water table depth, microtopography, and the spatial heterogeneity of the vegetation communities present. There is a disconnect between the measurement scales for CH 4 fluxes, which can be measured with chambers at one-meter resolution and eddy covariance towers at 100-1000 m, whereas model estimates are typically made at thẽ 100 km scale. Therefore, it is critical to upscale site level measurements to the larger scale for model comparison. As vegetation has a critical role in explaining the variability of CH 4 fluxes across the tundra landscape, we tested whether remotely-sensed maps of vegetation could be used to upscale fluxes to larger scales. The objectives of this study are to compare four different methods for mapping and two methods for upscaling plot-level CH 4 emissions to the measurements from EC towers. We show that linear discriminant analysis (LDA) provides the most accurate representation of the tundra vegetation within the EC tower footprints (classification accuracies of between 65% and 88%). The upscaled CH 4 emissions using the areal fraction of the vegetation communities showed a positive correlation (between 0.57 and 0.81) with EC tower measurements, irrespective of the mapping method. The area-weighted footprint model outperformed the simple area-weighted method, achieving a correlation of 0.88 when using the vegetation map produced with the LDA classifier. These results suggest that the high spatial heterogeneity of the tundra vegetation has a strong impact on the flux, and variation indicates the potential impact of environmental or climatic parameters on the fluxes. Nonetheless, assimilating remotely-sensed vegetation maps of tundra in a footprint model was successful in upscaling fluxes across scales.

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“…Bousquet et al, 2011;Berchet et al, 2015) or data-driven upscaling of eddycovariance-or chamber-based observations (e.g. Christensen et al, 1995;Marushchak et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

“…Regarding the assumptions concerning fluxes during winter time or plant transport, according to recent findings (Zona et al, 2016;Marushchak et al, 2016), the settings chosen within the context of this work might be oversimplifying the actual processes in the field. The implemented mechanism that prevents gas exchange with the atmosphere once the snow cover reaches a depth of 5 cm is a very crude approximation of the snow cover influence.…”

Section: Discussionmentioning

confidence: 99%

Process-based modelling of the methane balance in periglacial landscapes (JSBACH-methane)

et al. 2017

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Abstract. A detailed process-based methane module for a global land surface scheme has been developed which is general enough to be applied in permafrost regions as well as wetlands outside permafrost areas. Methane production, oxidation and transport by ebullition, diffusion and plants are represented. In this model, oxygen has been explicitly incorporated into diffusion, transport by plants and two oxidation processes, of which one uses soil oxygen, while the other uses oxygen that is available via roots. Permafrost and wetland soils show special behaviour, such as variable soil pore space due to freezing and thawing or water table depths due to changing soil water content. This has been integrated directly into the methane-related processes. A detailed application at the Samoylov polygonal tundra site, Lena River Delta, Russia, is used for evaluation purposes. The application at Samoylov also shows differences in the importance of the several transport processes and in the methane dynamics under varying soil moisture, ice and temperature conditions during different seasons and on different microsites. These microsites are the elevated moist polygonal rim and the depressed wet polygonal centre. The evaluation shows sufficiently good agreement with field observations despite the fact that the module has not been specifically calibrated to these data. This methane module is designed such that the advanced land surface scheme is able to model recent and future methane fluxes from periglacial landscapes across scales. In addition, the methane contribution to carbon cycleclimate feedback mechanisms can be quantified when running coupled to an atmospheric model.

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Methane dynamics in the subarctic tundra: combining stable isotope analyses, plot- and ecosystem-scale flux measurements

Cited by 48 publications

References 50 publications

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

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

Upscaling CH4 Fluxes Using High-Resolution Imagery in Arctic Tundra Ecosystems

Process-based modelling of the methane balance in periglacial landscapes (JSBACH-methane)

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