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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-269
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-269
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 26 Jul 2019

Submitted as: research article | 26 Jul 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

Metabolic tradeoffs and heterogeneity in microbial responses to temperature determine the fate of litter carbon in a warmer world

Grace Pold1, Seeta A. Sistla2, and Kristen M. DeAngelis3 Grace Pold et al.
  • 1Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
  • 2Natural Resources Management and Environmental Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA
  • 3Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA

Abstract. Climate change has the potential to destabilize the Earth’s massive terrestrial carbon (C) stocks, but the degree to which models project this destabilization to occur depends on the kinds and complexities of microbial processes they simulate. Of particular note is carbon use efficiency (CUE), which determines the fraction of C processed by microbes that is anabolized into microbial biomass rather than being lost to the atmosphere as carbon dioxide. The temperature sensitivity of CUE is often modeled as a homogeneous property of the community, which contrasts with empirical data and has unknown impacts on projected changes to the soil carbon cycle under global warming. We used the DEMENT model – which simulates taxon-level litter decomposition dynamics – to explore the effects of introducing organism-level heterogeneity into the CUE response to temperature for decomposition of leaf litter under 5 °C of warming. We found that allowing CUE temperature response to differ between taxa facilitated increased loss of litter C, unless fungal taxa were specifically restricted to decreasing CUE with temperature. Increased loss of litter C was observed when the growth of a larger microbial biomass pool was fueled by higher community-level average CUE at higher temperature in the heterogeneous microbial community, with effectively lower costs for extracellular enzyme production. Together these results implicate a role for diversity of taxon-level CUE responses in driving the fate of litter C in a warmer world.

Grace Pold et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Grace Pold et al.
Model code and software

DEMENT model and parameterization Grace Pold (modified from original code by Steven Allison) https://doi.org/10.17605/OSF.IO/CWEP9

Grace Pold et al.
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Short summary
The litter decomposition model DEMENT was run under ambient temperatures and with 5C of warming. We found that the loss of litter carbon to the atmosphere as CO2 was exacerbated by warming when the microbes in the model differed in their temperature responses, compared to when all microbes responded identically to warming. Our results therefore indicate that predicted changes in litter carbon stocks are sensitive to heterogeneity in key parameters of soil decomposer physiology.
The litter decomposition model DEMENT was run under ambient temperatures and with 5C of warming....
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