Modeled Microbial Dynamics Explain the Apparent Temperature Sensitivity of Wetland Methane Emissions

Warming-induced carbon loss through terrestrial ecosystem respiration (Re) is likely getting stronger in high latitudes and cold regions because of the more rapid warming and higher temperature sensitivity of Re (Q10). However, it is not known whether the spatial relationship between Q10 and temperature also holds temporally under a future warmer climate. Here, we analyzed apparent Q10 values derived from multiyear observations at 74 FLUXNET sites spanning diverse climates and biomes. We found warming-induced decline in Q10 is stronger at colder regions than other locations, which is consistent with a meta-analysis of 54 field warming experiments across the globe. We predict future warming will shrink the global variability of Q10 values to an average of 1.44 across the globe under a high emission trajectory (RCP 8.5) by the end of the century. Therefore, warming-induced carbon loss may be less than previously assumed because of Q10 homogenization in a warming world.

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

Biogeosciences Discussions ◽

10.5194/bgd-12-445-2015 ◽

2015 ◽

Vol 12 (1) ◽

pp. 445-480 ◽

Cited By ~ 1

Author(s):

A. Malhotra ◽

N. T. Roulet

Keyword(s):

Temperature Sensitivity ◽

Structural Changes ◽

Co2 Flux ◽

Apparent Temperature ◽

Ecosystem Structure ◽

Environmental Correlates ◽

C Storage ◽

Discontinuous Permafrost ◽

Significant Area ◽

And Function

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

Biogeosciences ◽

10.5194/bg-12-3119-2015 ◽

2015 ◽

Vol 12 (10) ◽

pp. 3119-3130 ◽

Cited By ~ 14

Author(s):

A. Malhotra ◽

N. T. Roulet

Keyword(s):

Temperature Sensitivity ◽

Structural Changes ◽

Co2 Flux ◽

Apparent Temperature ◽

Ecosystem Structure ◽

Environmental Correlates ◽

C Storage ◽

Discontinuous Permafrost ◽

Significant Area ◽

And Function

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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Reduction of the temperature sensitivity of minerotrophic fen methane emissions by simulated glacial atmospheric carbon dioxide starvation

Journal of Geophysical Research Biogeosciences ◽

10.1002/jgrg.20017 ◽

2013 ◽

Vol 118 (2) ◽

pp. 462-470 ◽

Cited By ~ 3

Author(s):

Carl P. Boardman ◽

Vincent Gauci ◽

Andrew Fox ◽

Stephen Blake ◽

David J. Beerling

Keyword(s):

Carbon Dioxide ◽

Temperature Sensitivity ◽

Atmospheric Carbon Dioxide ◽

Methane Emissions ◽

Atmospheric Carbon

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Measurement depth effects on the apparent temperature sensitivity of soil respiration in field studies

Biogeosciences Discussions ◽

10.5194/bgd-5-1867-2008 ◽

2008 ◽

Vol 5 (3) ◽

pp. 1867-1898 ◽

Cited By ~ 5

Author(s):

A. Graf ◽

L. Weihermüller ◽

J. A. Huisman ◽

M. Herbst ◽

J. Bauer ◽

...

Keyword(s):

Soil Respiration ◽

Temperature Measurement ◽

Temperature Sensitivity ◽

Field Experiments ◽

Soil Surface ◽

Field Measurements ◽

Apparent Temperature ◽

Time Averaging ◽

Co2 Efflux ◽

Measurement Depth

Abstract. CO2 efflux at the soil surface is the result of respiration in different depths that are subjected to variable temperatures at the same time. Therefore, the temperature measurement depth affects the apparent temperature sensitivity of field-measured soil respiration. We summarize existing literature evidence on the importance of this effect, and describe a simple model to understand and estimate the magnitude of this potential error source for heterotrophic respiration. The model is tested against field measurements. We discuss the influence of climate (annual and daily temperature amplitude), soil properties (vertical distribution of CO2 sources, thermal and gas diffusivity), and measurement schedule (frequency, study duration, and time averaging). Q10 as a commonly used parameter describing the temperature sensitivity of soil respiration is taken as an example and computed for different combinations of the above conditions. We define conditions and data acquisition and analysis strategies that lead to lower errors in field-based Q10 determination. It was found that commonly used temperature measurement depths are likely to result in an underestimation of temperature sensitivity in field experiments. Our results also apply to activation energy as an alternative temperature sensitivity parameter.

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