Temperature Sensitivity of Methane Production in the Permafrost Active Layer at Stordalen, Sweden: A Comparison with Non-permafrost Northern Wetlands

Lupascu, Massimo; Wadham, Jemma L.; Hornibrook, Edward R. C.; Pancost, Richard D.

doi:10.1657/1938-4246-44.4.469

Cited by 65 publications

(71 citation statements)

References 74 publications

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“…One possibility is that the substantial differences we found between optimal rq10 values in the north and south represent real differences between the responses of soil microbial communities in those regions. This is somewhat corroborated by a recent synthesis of laboratory and field studies (Lupascu et al, 2012) that found higher mean Q 10 values for sphagnum-dominated wetlands than for sedge-dominated wetlands (means of 8 and 4.3, respectively), and higher (although not statistically significant) mean Q 10 values for nonpermafrost than permafrost wetlands.…”

Section: Spatial Variation Of Methane Emission Parameterssupporting

confidence: 63%

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

et al. 2013

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Abstract. We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948-2010. We found that, while surface heterogeneity (fractional saturated area) had little overall effect on estimates of the region's carbon fluxes, subsurface heterogeneity (spatial variations in water table depth) played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH 4 emissions recorded by intensive in situ observations across the domain, in which very little CH 4 is emitted north of 60 • N, it was necessary to (a) account for CH 4 emissions from unsaturated wetlands and (b) use spatially varying methane model parameters that reduced estimated CH 4 emissions in the northern (permafrost) half of the domain (and/or account for lower CH 4 emissions under inundated conditions). Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.

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Section: Spatial Variation Of Methane Emission Parameterssupporting

confidence: 63%

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

et al. 2013

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“…4a), applying one activation energy value to estimate landscape level CH 4 fluxes at Stordalen would not be appropriate and would likely require a set of parameterizations for the various thaw stages. Variable temperature sensitivities to C fluxes have been recognized in major thaw stages in the past (e.g., Lupascu and Wadham, 2012), but our study demonstrates that this variability is present even in the transitional stages. Furthermore, the multiple regression analyses for each thaw stages (Fig.…”

Section: Variable Changes In Ecosystem Relationships With Increasing contrasting

confidence: 42%

Environmental correlates of peatland carbon fluxes in a thawing landscape: do transitional thaw stages matter?

Malhotra

Roulet

2015

Biogeosciences

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Abstract. Peatlands in discontinuous permafrost regions occur as a mosaic of wetland types, each with variable sensitivity to climate change. Permafrost thaw further increases the spatial heterogeneity in ecosystem structure and function in peatlands. Carbon (C) fluxes are well characterized in endmember thaw stages such as fully intact or fully thawed permafrost but remain unconstrained for transitional stages that cover a significant area of thawing peatlands. Furthermore, changes in the environmental correlates of C fluxes, due to thaw, are not well described -a requirement for modeling future changes to C storage of permafrost peatlands. We investigated C fluxes and their correlates in end-member and a number of transitional thaw stages in a sub-arctic peatland. Across peatland-lumped CH 4 and CO 2 flux data had significant correlations with expected correlates such as water table depth, thaw depth, temperature, photosynthetically active radiation and vascular green area. Within individual thaw states, bivariate correlations as well as multiple regressions between C flux and environmental factors changed variably with increasing thaw. The variability in directions and magnitudes of correlates reflects the range of structural conditions that could be present along a thaw gradient. These structural changes correspond to changes in C flux controls, such as temperature and moisture, and their interactions. Temperature sensitivity of CH 4 increased with increasing thaw in bivariate analyses, but lack of this trend in multiple regression analyses suggested cofounding effects of substrate or water limitation on the apparent temperature sensitivity. Our results emphasize the importance of incorporating transitional stages of thaw in landscape level C budgets and highlight that end-member or adjacent thaw stages do not adequately describe the variability in structure-function relationships present along a thaw gradient.

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“…However, gas production was linear over the incubations (Fig. S1), and Lupascu et al (29) found similar relative differences in methanogenesis between Sphagnum and sedge peat from Stordalen when incubated at 4°C, 14°C, and 24°C. The lower CH 4 /CO 2 ratios in the early part of the thaw sequence are also consistent with bog DOM's higher oxidation state and organic oxygen content relative to fen DOM ( Fig.…”

Section: Discussionmentioning

confidence: 56%

“…Intact palsa sites were not included in this study because their dry, aerobic status prevents meaningful comparison with other sites based on anaerobic incubations and DOM measurements. Previous measurements of CH 4 and CO 2 fluxes from palsas have shown that they produce negligible amounts or even consume ambient CH 4 (23,28,29) but are a net source of CO 2 (28).…”

Section: Study Site and Habitat Classificationmentioning

confidence: 99%

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

Hodgkins¹,

Tfaily²,

McCalley

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

290

362

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Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH 4 ) vs. carbon dioxide (CO 2 ) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently-to fully thawed sites in Stordalen Mire (68.35°N,19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH 4 and CO 2 production potentials, higher relative CH 4 /CO 2 ratios, and a shift in CH 4 production pathway from CO 2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH 4 . This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes.H igh-latitude soils in the Northern Hemisphere contain an estimated 1,400-1,850 petagrams (Pg) of carbon, of which ∼277 Pg is in peatlands within the permafrost zone (1, 2). This quantity of 277 Pg represents over one-third of the carbon stock in the atmosphere (ca. 800 Pg) (3). The fate of this carbon in a warming climate-i.e., the responses of net carbon balance and CH 4 emissions-is important in predicting climate feedbacks of permafrost thaw. Although northern peatlands are currently a net carbon sink, and have been since the end of the last glaciation, they are a net source of CH 4 (4, 5), emitting 0.046-0.09 Pg of carbon as CH 4 per year (4, 6, 7). Due to CH 4 's disproportionate global warming potential (33× CO 2 for 1 kg CH 4 vs. 1 kg CO 2 at a 100-y timescale) (8), this is equivalent to 6-12% of annual fossil fuel emissions of CO 2 (8.7 Pg of C) (9). The thaw of permafrost peatlands may alter their CH 4 and CO 2 emissions due to mobilization of formerly frozen carbon, higher temperatures, altered redox conditions, and evolving organic matter chemistry. Changes in carbon emissions, and in CH 4 emission in particular, could have potentially significant climate impacts. CH 4 is produced by two primary mechanisms (10-12),...

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Temperature Sensitivity of Methane Production in the Permafrost Active Layer at Stordalen, Sweden: A Comparison with Non-permafrost Northern Wetlands

Cited by 65 publications

References 74 publications

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

Environmental correlates of peatland carbon fluxes in a thawing landscape: do transitional thaw stages matter?

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

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