A parameterization of respiration in frozen soils based on substrate  availability

Schaefer, Kevin; Jafarov, Elchin

doi:10.5194/bg-13-1991-2016

Cited by 40 publications

(33 citation statements)

References 39 publications

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“…High-latitude C and N dynamic models such as Simple Biosphere/Carnegie-Ames-Stanford Approach (SiBCASA) focuses on extracellular parameters and only the thawing of permafrost is assumed to increase CO 2 emission (Schaefer et al, 2011; Schaefer and Jafarov, 2016). This increase is likely to be overestimated because permafrost soils—even if completely frozen at low temperatures—exhibit considerable microbial activity.…”

Section: Resultsmentioning

confidence: 99%

“…Microbial activity has been detected in soil down to -39°C (Panikov et al, 2006; Schaefer and Jafarov, 2016). This has evoked interest in the adaptive metabolic mechanisms of microorganisms at such extremely low temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…Metabolic activity has been detected in soil at temperatures as low as -39°C (Panikov et al, 2006; Schaefer and Jafarov, 2016) and an absence of subzero temperature limit for microbial metabolism was suggested by Price and Sowers (2004). Although biogeochemical models designed to simulate C and N dynamics in high-latitude ecosystems incorporate extracellular parameters (Schaefer and Jafarov, 2016), molecular and biochemical adaptations responsible for microbial freeze tolerance remain unclear. This knowledge gap hampers the estimation of C balances and ecosystem feedback responses.…”

Section: Introductionmentioning

confidence: 99%

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Microbial Metabolism in Soil at Subzero Temperatures: Adaptation Mechanisms Revealed by Position-Specific 13C Labeling

et al. 2017

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Although biogeochemical models designed to simulate carbon (C) and nitrogen (N) dynamics in high-latitude ecosystems incorporate extracellular parameters, molecular and biochemical adaptations of microorganisms to freezing remain unclear. This knowledge gap hampers estimations of the C balance and ecosystem feedback in high-latitude regions. To analyze microbial metabolism at subzero temperatures, soils were incubated with isotopomers of position-specifically 13C-labeled glucose at three temperatures: +5 (control), -5, and -20°C. 13C was quantified in CO2, bulk soil, microbial biomass, and dissolved organic carbon (DOC) after 1, 3, and 10 days and also after 30 days for samples at -20°C. Compared to +5°C, CO2 decreased 3- and 10-fold at -5 and -20°C, respectively. High 13C recovery in CO2 from the C-1 position indicates dominance of the pentose phosphate pathway at +5°C. In contrast, increased oxidation of the C-4 position at subzero temperatures implies a switch to glycolysis. A threefold higher 13C recovery in microbial biomass at -5 than +5°C points to synthesis of intracellular compounds such as glycerol and ethanol in response to freezing. Less than 0.4% of 13C was recovered in DOC after 1 day, demonstrating complete glucose uptake by microorganisms even at -20°C. Consequently, we attribute the fivefold higher extracellular 13C in soil than in microbial biomass to secreted antifreeze compounds. This suggests that with decreasing temperature, intracellular antifreeze protection is complemented by extracellular mechanisms to avoid cellular damage by crystallizing water. The knowledge of sustained metabolism at subzero temperatures will not only be useful for modeling global C dynamics in ecosystems with periodically or permanently frozen soils, but will also be important in understanding and controlling the adaptive mechanisms of food spoilage organisms.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microbial Metabolism in Soil at Subzero Temperatures: Adaptation Mechanisms Revealed by Position-Specific 13C Labeling

et al. 2017

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“…In order to quantify the influence of snow heterogeneity on soil thermal dynamics, a dynamic process-based snow model is needed (Broxton et al, 2015;Hiemstra et al, 2002Hiemstra et al, , 2006. Further, unfrozen water has been indicated important in affecting winter soil respiration (Schaefer & Jafarov, 2016). Future model development could benefit from better soil moisture simulation in response to freezethaw dynamics.…”

Section: 1002/2017jg003864mentioning

confidence: 99%

Quantifying the Effects of Snowpack on Soil Thermal and Carbon Dynamics of the Arctic Terrestrial Ecosystems

Lyu

Zhuang

2018

JGR Biogeosciences

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Snow insulation effects modify soil and carbon dynamics in northern middle to high latitudes (45°–90°N). This study incorporates these effects by introducing a snow model into an existing soil thermal model in a biogeochemistry modeling framework, the Terrestrial Ecosystem Model. The coupled model is used to quantify snow insulation effects on carbon and soil thermal dynamics in 45°–90°N region for the historical period (2003–2010) and the future period (2017–2099) under two climate scenarios. The revised model captures the snow insulation effects and improves the estimates of soil thermal dynamics and the land freeze‐thaw as well as terrestrial ecosystem carbon dynamics. Historical mean cold‐season soil temperature at 5 cm depth driven with satellite‐based snow data is 6.4°C warmer in comparison with the original model simulation. Frozen area in late spring is estimated to shrink mainly over eastern Siberia, in central to eastern Europe, and along southern Canada in November. During each nongrowing season in the historical period, 0.41 Pg more soil C is released due to warmer soil temperature estimated using the new model. During 2003–2010, the revised model estimates that the region accumulated 0.86 Pg less C due to weaker gross primary production, leading to a regional C loss at 0.19 PgC/year. The revised model projects that the region will lose 38–51% permafrost area by 2100 and continue to be a C source under the low‐emission scenario (Representative Concentration Pathway 2.6) but to be gradually transitioning into a weak sink in the latter half of the 21st century under the high‐emission scenario (Representative Concentration Pathway 8.5).

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“…43 The soil model separately tracks liquid water, ice, and frozen organic matter at each time step as prognostic variables, accounting for the effects of latent heat. 6,44 SiBCASA separately tracks CO 2 and methane emissions.…”

Section: Emulator For Nonlinear Permafrost Carbon Feedback Based On Smentioning

confidence: 99%

Climate Policy Implications of Nonlinear Decline of Arctic Land Permafrost and Sea Ice

Yumashev¹,

Hope²,

Schaefer³

et al. 2017

Preprint

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Arctic feedbacks will accelerate climate change and could jeopardise mitigation efforts. The permafrost carbon feedback releases carbon to the atmosphere from thawing permafrost and the sea ice albedo feedback increases solar absorption in the Arctic Ocean. A constant positive albedo feedback and zero permafrost feedback have been used in nearly all climate policy studies to date, while observations and models show that the permafrost feedback is significant and that both feedbacks are nonlinear. Using novel dynamic emulators in the integrated assessment model PAGE-ICE, we investigate nonlinear interactions of the two feedbacks with the climate and economy under a range of climate scenarios consistent with the Paris Agreement. The permafrost feedback interacts with the land and ocean carbon uptake processes, and the albedo feedback evolves through a sequence of nonlinear transitions associated with the loss of Arctic sea ice in different months of the year. The US's withdrawal from the current national pledges could increase the total discounted economic impact of the two Arctic feedbacks until 2300 by $25 trillion, reaching nearly $120 trillion, while meeting the 1.5 °C and 2 °C targets will reduce the impact by an order of magnitude. from thawing permafrost, i and the sea ice-albedo feedback (SIAF) 8,9 increases solar absorption in the Arctic Ocean. Despite significant advances documented by the 5 th IPCC Assessment Report, projections of future climate using state-of-the-art Earth system models (ESMs) from the CMIP5 project do not include PCF, 10,11 although several models will incorporate the PCF in the 6 th assessment report. Keywordsii Consequently, most climate policy assessments based on results from the ESMs underestimate the extent of warming in response to anthropogenic emissions. The SIAF, on the other hand, is present in climate projections by the ESMs through the coupling of sea ice models to atmosphere and ocean models. 10 However, existing estimates of the total economic impact of climate change under different policy assumptions using integrated assessment models (IAMs) assume that radiative forcing from SIAF increases linearly with global mean temperature, which is inconsistent with the predictions of the ESMs.iiiThe Paris Agreement of December 2015 sets out ambitious targets to "limit global mean temperature rise well below 2°C and, if possible, below 1.5°C above pre-industrial levels," which are more challenging than the current set of intended nationally determined contributions (INDCs). 12 Achieving these targets represents a significant challenge to the international community. 13,14 The framework set out by the Paris Agreement and its implementation continue to face political hurdles, epitomised by the recent decision of the United States Federal Government to withdraw from it. 15PCF and SIAF represent three of the thirteen main tipping elements the Earth's climate system identified in a recent survey by Schellnhuber et al. 16 Tipping elements are physical processes acting as posi...

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A parameterization of respiration in frozen soils based on substrate availability

Cited by 40 publications

References 39 publications

Microbial Metabolism in Soil at Subzero Temperatures: Adaptation Mechanisms Revealed by Position-Specific 13C Labeling

Microbial Metabolism in Soil at Subzero Temperatures: Adaptation Mechanisms Revealed by Position-Specific 13C Labeling

Quantifying the Effects of Snowpack on Soil Thermal and Carbon Dynamics of the Arctic Terrestrial Ecosystems

Climate Policy Implications of Nonlinear Decline of Arctic Land Permafrost and Sea Ice

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