04 Jul 2022
04 Jul 2022
Status: this preprint is open for discussion.

Upscaling microbial stoichiometric adaptability in SOM turnover: The SESAM Soil Enzyme Steady Allocation Model (v3.0)

Thomas Wutzler1, Lin Yu1,2, Marion Schrumpf1, and Sönke Zaehle1 Thomas Wutzler et al.
  • 1Max Planck Institute for Biogeochemistry, Hans-Knöll-Straße 10, 07745 Jena, Germany
  • 2Centre for Environmental and Climate Science (CEC) at Lund University, Sölvegatan 37, Lund, Sweden

Abstract. Understanding the coupling of nitrogen (N) and carbon (C) cycles of land ecosystems, requires understanding microbial element use efficiencies of soil organic matter (SOM) decomposition. Whereas important controls of those efficiencies by microbial community adaptations have been shown at the scale of a soil pore, a simplified representation of those controls is needed at the ecosystem scale. However, without abstracting from the many details, models are not identifiable, i.e. can not be fitted without ambiguities to observations. There is a need to find, implement, and validate abstract simplified formulations of theses processes.

Therefore, we developed the SESAM model as an ab- straction of the more detailed soil enzyme allocation model (SEAM) model and tested, whether it can provide the same decadal-term predictions. SEAM explicitly models community adaptation strategies of resource allocation to extracellular enzymes and enzyme limitations on SOM decomposition. It thus provides a scaling from representing several microbial functional groups to a single holistic microbial community. Here we further abstracted the model using quasi-steady-state assumption for extracellular enzyme pools to derive the SESAM model.

SESAM reproduced the priming effect, the SOM banking mechanism, and the damping of fluctuations of carbon use efficiency with microbial competition as predicted by SEAM and other more detailed models. This development is an important step towards more parsimonious representation of soil microbial effects in global land surface models.

Thomas Wutzler et al.

Status: open (until 29 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-359', Anonymous Referee #1, 05 Aug 2022 reply
  • RC2: 'Comment on egusphere-2022-359', Nadezda Vasilyeva, 12 Aug 2022 reply

Thomas Wutzler et al.

Thomas Wutzler et al.


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Short summary
Soil microbes process soil organic matter and affect carbon storage and plant nutrition at ecosystem scale. We hypothesized that decadal dynamics is constrained by the ratios of elements in litter inputs, microbes and matter and that microbial community optimizes growth. This allowed the SESAM model to descibe decadal-term carbon sequestration in soils and other biogeochemical processes explicitly accounting for microbial processes but without its problematic fine-scale parameterization.