CE-DYNAM (v1): a spatially explicit process-based carbon erosion scheme for use in Earth system models

Naipal, Victoria; Lauerwald, Ronny; Ciais, Philippe; Guenet, Bertrand; Wang, Yilong

doi:https://doi.org/10.5194/gmd-13-1201-2020

Articles | Volume 13, issue 3

https://doi.org/10.5194/gmd-13-1201-2020

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

https://doi.org/10.5194/gmd-13-1201-2020

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

Articles | Volume 13, issue 3

Model description paper

|

17 Mar 2020

Model description paper |

| 17 Mar 2020

CE-DYNAM (v1): a spatially explicit process-based carbon erosion scheme for use in Earth system models

Victoria Naipal, Ronny Lauerwald, Philippe Ciais, Bertrand Guenet, and Yilong Wang

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Final revised paper (published on 17 Mar 2020)
Supplement to the final revised paper
Preprint (discussion started on 11 Jun 2019)
Supplement to the preprint

Interactive discussion

Status: closed

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

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RC1: 'Review for GMD-2019-110', Anonymous Referee #1, 15 Jul 2019
- AC1: 'Response to Reviewer 1', Victoria Naipal, 05 Sep 2019
RC2: 'Comments to authors', Anonymous Referee #2, 23 Jul 2019
- AC2: 'Response to Reviewer 2', Victoria Naipal, 05 Sep 2019

Peer-review completion

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

AR by Victoria Naipal on behalf of the Authors (27 Sep 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Oct 2019) by Andrew Yool

RR by Anonymous Referee #1 (29 Oct 2019)

Suggestions for revision or reasons for rejection

Thanks for the detailed response. It indeed clarifies many things.
If I understand correctly, because the long sediment residence time in downstream grid cells near to the river mouth (Fig. S2), the sediment and C export from the river to the sea should be mainly controlled by the sediment and C budget in those downstream grid cells. Using the value of sediment export (1.6×10^7 tons yr-1) and the value of C export (0.0095×10^12 gC yr-1), I calculated that the C density in those grid cells is only 6×10^-5 gC g-1. This is extremely low. I suspect that the simulated C density in other grid cells of large sediment residence times is also low.
Because the authors have explained that their focus is on the impact of soil erosion and deposition on land C dynamics in the revision, I actually agree that it is not important to make the simulated export of sediment and C to the sea match the observations. However, as said above, the problem of simulating C dynamics over floodplain cannot be ignored. I am not sure whether the problem is on the CE-DYNAM side or the ORCHIDEE side. Could you compare the surface layer C density in grid cells of long residence time between S0 and S2 to identify the cause? If it is on the CE-DYNAM side, further model improvement is needed.
Other comments
1) There are Hoffmann et al. (2013a & 2013b) in the references but only Hoffmann et al. (2013) is cited. Please clarify.
2) When checked Naipal et al. (2016), I noticed that simulated sediment storage can be an order of magnitude lower than the observations, even they show the similar scaling factors. How is the absolute value of simulated C storage compared with Hoffmann et al. (2013a)?
3) Eq. 6: Is this residence time equation universal in the world since the authors emphasized that the model would be applied globally?
4) L436: Should be “lose” not “loose”.
5) Could you explain what is net soil erosion? Is this the eroded sediment deposited to the floodplain fraction?
6) Please define NPP and NEP before using abbreviations.
7) L548–449: Table 3 shows that the result of simulated net soil erosion is not good as described. Can be possibly related to my first comment?
8) L555-557: Sorry, I do not understand the mechanism. How can erosion-control and management practice affect this relationship?
9) Figure 3A: Why is the simulation missed in some bins?

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RR by Anonymous Referee #3 (04 Nov 2019)

Suggestions for revision or reasons for rejection

The manuscript presents a consistent and interesting study concerning carbon and erosion modelling. Authors presented the model CE-DYNAM which integrates sediment snd C dynamics (structure, concepts, limitations and evaluation) applied at Rhine catchment scale during the period 1850-2005 AD. The study contributes to model soil organic carbon stock changes using a process‐based model and to the evaluation of strategies to mitigate climate change at large scale.

Before publishing some minor revision should be addressed:
Line 61 "Most studies modeling soil erosion and its net effect on SOC dynamics at global
scale" Please include references. Similarly in line 65
Line 107 Define Gross Primary Production
Lines 132- 136 slope-length (describing the influence of topography on soil erosion risk.)
The following sentence refers to slope-length? Revise: “These factors are a function of local manmade structures and management practices”
Please clarify “we focus in this study on potential soil erosion and do not consider erosion-control practices”
Line 153 similar catchments or not?
I recommend using past tense lines 190, 194, 210
Line 191 “reducing the sediment transport from hillslopes to floodplains” this cannot be alid for some other regions then line 153 could be revised as follows: “should be also applicable for other similar catchments
Line 236 revise: “discretization scheme SOC scheme”
Line 397 contrasting
Line 468 Please specify to highlight the new contribution of the study
Line 479 Furthermore,
Line 518 avoid repetition “such as in our study. In our study”
Lines 519, 152, I suggest to include also in line 84
Line 544 how about slope-length?
Line 585 “started around 1910 AD” Include a reference/source
Line 604 Figs
Line 659 chapter? Section
Line 671-674 Move to introduction
Line 679 I recommend using past tense as in line 689
Line 750 due to this limitation I suggest to revise the sentences in lines 87-88 and line 153 (globally); 689-690
Line 821 showed as in line 817. Please revise in the whole manuscript and keep the same tense

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ED: Reconsider after major revisions (18 Nov 2019) by Andrew Yool

AR by Victoria Naipal on behalf of the Authors (23 Jan 2020) Author's response Manuscript

ED: Publish subject to technical corrections (07 Feb 2020) by Andrew Yool

Short summary

In this study we present the Carbon Erosion DYNAMics model (CE-DYNAM) that links sediment dynamics resulting from water erosion with the soil carbon cycle along a cascade of hillslopes, floodplains, and rivers. The model can simulate the removal of soil and carbon from eroding areas and their destination at regional scale. We calibrated and validated the model for the Rhine catchment, and we show that soil erosion is a potential large net carbon sink over the period 1850–2005.