Dynamic upscaling of decomposition kinetics for carbon cycling models

Chakrawal, Arjun; Herrmann, Anke M.; Koestel, John; Jarsjö, Jerker; Nunan, Naoise; Kätterer, Thomas; Manzoni, Stefano

doi:https://doi.org/10.5194/gmd-13-1399-2020

Articles | Volume 13, issue 3

https://doi.org/10.5194/gmd-13-1399-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-13-1399-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 3

Development and technical paper

|

23 Mar 2020

Development and technical paper |

| 23 Mar 2020

Dynamic upscaling of decomposition kinetics for carbon cycling models

Arjun Chakrawal, Anke M. Herrmann, John Koestel, Jerker Jarsjö, Naoise Nunan, Thomas Kätterer, and Stefano Manzoni

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Final revised paper (published on 23 Mar 2020)
Preprint (discussion started on 02 Jul 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Start of development of new class of models', Thomas Wutzler, 06 Jul 2019
- AC1: 'Initial reply to Thomas Wutzler's comments', Arjun Chakrawal, 25 Jul 2019
- AC2: 'Final response', Arjun Chakrawal, 25 Sep 2019
RC2: 'Interactive comment on “Dynamic upscaling of decomposition kinetics for carbon cycling models” by Chakrawal et al.', Ali Ebrahimi, 23 Aug 2019
- AC3: 'Final response', Arjun Chakrawal, 25 Sep 2019
RC3: 'An interesting study but needs significant improvement.', Anonymous Referee #3, 25 Aug 2019
- AC4: 'Final response', Arjun Chakrawal, 25 Sep 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Arjun Chakrawal on behalf of the Authors (24 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Oct 2019) by Wolfgang Kurtz

RR by Thomas Wutzler (07 Nov 2019)

Suggestions for revision or reasons for rejection

The authors acknowledged almost all my concerns. The approach of getting the results from only the numerical model and the limitations of the study are now better described.

One thing I still missing is some discussion of the stable pattern of heterogeneities formed at the final states:
From Fig. A3f I get that the second order terms are zero except the negative covariance between deposition rate and substrate concentration for the multiplicative decomposition model. I interpret this as a shift in substrate quality (higher concentrations of low quality) than the original loguniform distribution of substrate qualities. And this to me explains the higher new steady-state stocks for the same given substrate input. For the other decomposition models, I do not find such information, but there seems to be a fundamental difference with the MM decomposition, which has positive sum of higher order terms for a longer time.

Minor comments:

Abstract sentence at line 15 is hard to parse. After my first reading I got – “It was not possible”. Hence I suggest reordering to: “The homogenous model assumption was not able to capture … Only the inclusion of second order moments ...”

page 7: symbol D is used both for diffusion coefficient and for decomposition. I suggest to distinguish the diffusion coefficient by an subscript.

P9L13: What are the implications or complications of dropping the assumption of spatially invariant Y and I?

P12L10: Why do Cb and k need the averaging bar here? Better call Cb an initial condition rather than model parameter.

P20 Fig4: By looking at the y-axis scales I noticed that you have quite high microbial biomass per organic matter (Cs+Cb) of about 15% which you report being still low compared to half-saturation Km. Did you have any incubation experiment experiment in mind, i.e. of which soil is your simulation representative for?

P22L13 and Fig.6. I missed some discussion why the sumSOT is behaving so differently for the MM kinetics in the full heterogeneity compared to the other kinetics.

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RR by Anonymous Referee #3 (15 Nov 2019)

ED: Reconsider after major revisions (23 Nov 2019) by Wolfgang Kurtz

AR by Arjun Chakrawal on behalf of the Authors (04 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 Jan 2020) by Wolfgang Kurtz

RR by Thomas Wutzler (23 Jan 2020)

RR by Anonymous Referee #3 (29 Jan 2020)

ED: Publish subject to technical corrections (08 Feb 2020) by Wolfgang Kurtz

AR by Arjun Chakrawal on behalf of the Authors (11 Feb 2020) Manuscript

Short summary

Soils are heterogeneous, which results in a nonuniform spatial distribution of substrates and the microorganisms feeding on them. Our results show that the variability in the spatial distribution of substrates and microorganisms at the pore scale is crucial because it affects how fast substrates are used by microorganisms and thus the decomposition rate observed at the soil core scale. This work provides a methodology to include microscale heterogeneity in soil carbon cycling models.