Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 10
Biogeosciences, 12, 3119–3130, 2015
https://doi.org/10.5194/bg-12-3119-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Freshwater ecosystems in changing permafrost landscapes

Biogeosciences, 12, 3119–3130, 2015
https://doi.org/10.5194/bg-12-3119-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 May 2015

Research article | 29 May 2015

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

A. Malhotra and N. T. Roulet A. Malhotra and N. T. Roulet
  • Department of Geography, McGill University, Montreal, Quebec, Canada

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 end-member 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 CH4 and CO2 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 CH4 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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We found that the dominant abiotic and biotic correlates of CO2 and CH4 fluxes change in strength and interactions as permafrost thaw progresses in a sub-arctic peatland. Our results emphasize the importance of incorporating transitional stages of thaw in landscape-level C budgets and highlight that end-member thaw stages do not adequately describe the variability in structure-function relationships present along a thaw gradient.
We found that the dominant abiotic and biotic correlates of CO2 and CH4 fluxes change in...
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