Model formulation of microbial CO2 production and efficiency can significantly influence short and long term soil C projections

Ballantyne, Ford; Billings, Sharon A.

doi:10.1038/s41396-018-0085-1

Cited by 13 publications

(11 citation statements)

References 21 publications

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“…Microbial parameters are typically estimated from short‐term studies and it is still unclear to what extent these parameters can be extrapolated to longer time scales. Indeed, microbial responses to warming change over time (Ballantyne & Billings, ; Walker et al, ), for example, the progressive shifts from cellulase to ligninase activities identified in this meta‐analysis. Thus, keeping microbial parameters constant with warming duration may lead to inaccurate ESM predictions.…”

Section: Discussionmentioning

confidence: 89%

Soil carbon loss with warming: New evidence from carbon‐degrading enzymes

Chen

Elsgaard

Groenigen

et al. 2020

Global Change Biology

176

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Climate warming affects soil carbon (C) dynamics, with possible serious consequences for soil C stocks and atmospheric CO2 concentrations. However, the mechanisms underlying changes in soil C storage are not well understood, hampering long‐term predictions of climate C‐feedbacks. The activity of the extracellular enzymes ligninase and cellulase can be used to track changes in the predominant C sources of soil microbes and can thus provide mechanistic insights into soil C loss pathways. Here we show, using meta‐analysis, that reductions in soil C stocks with warming are associated with increased ratios of ligninase to cellulase activity. Furthermore, whereas long‐term (≥5 years) warming reduced the soil recalcitrant C pool by 14%, short‐term warming had no significant effect. Together, these results suggest that warming stimulates microbial utilization of recalcitrant C pools, possibly exacerbating long‐term climate‐C feedbacks.

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Section: Discussionmentioning

confidence: 89%

Soil carbon loss with warming: New evidence from carbon‐degrading enzymes

Chen

Elsgaard

Groenigen

et al. 2020

Global Change Biology

176

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“…Assuming assimilation efficiency is temperature sensitive rather than maintenance respiration would cause models to overestimate the response of soil C stocks to temperature. In addition, Ballantyne and Billings (2018) found that whether respiration is modeled as function of biomass or as a function of uptake can also produce different transient responses in modeled SOC stocks, suggesting differences between these two processes might be even larger under dynamic environmental conditions like those modeled at the Earth system level. Currently most of the data on soil microbial CUE comes from studies using the C isotopic tracer method, which mainly reflects microbial assimilation efficiency.…”

Section: Implications For Models and Measurementsmentioning

confidence: 99%

Evaluating soil microbial carbon use efficiency explicitly as a function of cellular processes: implications for measurements and models

2018

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Carbon use efficiency (CUE), the proportion of carbon (C) consumed by microbes that is converted into biomass, is an important parameter for soil C models with explicit microbial controls. While often considered as a single parameter, CUE is an emergent property of multiple microbial processes, including assimilation efficiency, biomassspecific respiration, enzyme production, and respiratory costs of enzyme production. These processes occur over variable time scales and imply different fates for C, and the same emergent CUE value can result when C is allocated in fundamentally different ways (e.g. a high investment in enzyme production vs. a high assimilation cost). We developed a model that represents the individual processes underlying emergent CUE to test how shifts in microbial allocation alter equilibrium soil C pool sizes. We found that an increase in emergent CUE that results from a change in assimilation efficiency, biomass specific respiration, or respiration costs from enzyme production causes soil organic C (SOC) to decline, while the same change in emergent CUE resulting from a change in enzyme production causes SOC to increase. We also used the model to test the sensitivity of CUE from isotopic C tracer estimates to changes in microbial allocation processes. We found that these estimates do not account for the same microbial processes represented by emergent CUE in models. We propose that considering microbial processes explicitly rather than representing CUE as a single parameter can improve data-model integration. In addition, modeling microbial processes explicitly will account for a wider range of possible outcomes from shifts in microbial C allocation, such as when increased SOC results from increasing CUE.

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“…A wealth of emerging experimental and observational data have led to questions about the validity of this approach, suggesting instead that a diverse suite of microbial responses to the thermal regime drives soil C losses with warming (Frey, Lee, Melillo, & Six, ; Hagerty et al, ; Karhu et al, ; Walker et al, ). Furthermore, a proliferation of new models explicitly including microbial physiological and community dynamics show that soil C persistence and vulnerability to warming strongly depend on how such microbial processes are represented (Allison, Wallenstein, & Bradford, ; Ballantyne IV & Billings, ; Georgiou, Abramoff, Harte, Riley, & Torn, ). However, the validity of these representations, and hence their ability to build confidence in hypothesized microbial and soil C responses to warming, is still compromised because projections are rarely tested against measured data across a wide range of temperatures.…”

Section: Introductionmentioning

confidence: 99%

Increasing microbial carbon use efficiency with warming predicts soil heterotrophic respiration globally

Bradford

Dacal

et al. 2019

Global Change Biology

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The degree to which climate warming will stimulate soil organic carbon (SOC) losses via heterotrophic respiration remains uncertain, in part because different or even opposite microbial physiology and temperature relationships have been proposed in SOC models. We incorporated competing microbial carbon use efficiency (CUE)mean annual temperature (MAT) and enzyme kinetic-MAT relationships into SOC models, and compared the simulated mass-specific soil heterotrophic respiration rates with multiple published datasets of measured respiration. The measured data included 110 dryland soils globally distributed and two continental to global-scale cross-biome datasets. Model-data comparisons suggested that a positive CUE-MAT relationship best predicts the measured mass-specific soil heterotrophic respiration rates in soils distributed globally. These results are robust when considering models of increasing complexity and competing mechanisms driving soil heterotrophic respiration-MAT relationships (e.g., carbon substrate availability). Our findings suggest that a warmer climate selects for microbial communities with higher CUE, as opposed to the often hypothesized reductions in CUE by warming based on soil laboratory assays. Our results help to build the impetus for, and confidence in, including microbial mechanisms in soil biogeochemical models used to forecast changes in global soil carbon stocks in response to warming. K E Y W O R D S CO 2 efflux, global warming, microbe, soil carbon stock, soil respiration | 3355 YE Et al. S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Ye J-S, Bradford MA, Dacal M, Maestre FT, García-Palacios P. Increasing microbial carbon use efficiency with warming predicts soil heterotrophic respiration globally. Glob Change Biol. 2019;25:3354-3364.

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Model formulation of microbial CO2 production and efficiency can significantly influence short and long term soil C projections

Cited by 13 publications

References 21 publications

Soil carbon loss with warming: New evidence from carbon‐degrading enzymes

Soil carbon loss with warming: New evidence from carbon‐degrading enzymes

Evaluating soil microbial carbon use efficiency explicitly as a function of cellular processes: implications for measurements and models

Increasing microbial carbon use efficiency with warming predicts soil heterotrophic respiration globally

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