Accounting for carbon and nitrogen interactions in the global terrestrial ecosystem model ORCHIDEE (trunk version, rev 4999): multi-scale evaluation of gross primary production

Vuichard, Nicolas; Messina, Palmira; Luyssaert, Sebastiaan; Guenet, Bertrand; Zaehle, Sönke; Ghattas, Josefine; Bastrikov, Vladislav; Peylin, Philippe

doi:https://doi.org/10.5194/gmd-12-4751-2019

Articles | Volume 12, issue 11

https://doi.org/10.5194/gmd-12-4751-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-12-4751-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 11

Model evaluation paper

|

20 Nov 2019

Model evaluation paper |

| 20 Nov 2019

Accounting for carbon and nitrogen interactions in the global terrestrial ecosystem model ORCHIDEE (trunk version, rev 4999): multi-scale evaluation of gross primary production

Nicolas Vuichard, Palmira Messina, Sebastiaan Luyssaert, Bertrand Guenet, Sönke Zaehle, Josefine Ghattas, Vladislav Bastrikov, and Philippe Peylin

Download

Final revised paper (published on 20 Nov 2019)
Preprint (discussion started on 08 Nov 2018)

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'Review of manuscript gmd-2018-261', Anonymous Referee #1, 14 Dec 2018
- AC1: 'Responses to Referee #1', N. Vuichard, 14 Jun 2019
RC2: 'Review of « Accounting for Carbon and Nitrogen interactions in the Global Terrestrial Ecosystem Model ORCHIDEE (trunk version, rev 4999): multi-scale evaluation of gross primary production»', Anonymous Referee #2, 26 Mar 2019
- AC2: 'Responses to Referee #2', N. Vuichard, 14 Jun 2019

Peer-review completion

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

AR by N. Vuichard on behalf of the Authors (18 Jun 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Jul 2019) by Gerd A. Folberth

RR by Anonymous Referee #3 (08 Aug 2019)

Suggestions for revision or reasons for rejection

This is a well-written paper which documents important developments to the ORCHIDEE model. I have a few minor comments for clarification.

Transpiration: The N limitation reduces GPP and reduces water loss through transpiration. This is an important impact of the developments in ORCHIDEE, and it is mentioned throughout the manuscript. How do these results fit within current understanding of the linked hydrologic cycle responses to a coupled CN cycle? At the moment this is not mentioned in the Introduction but I think it should be. Also, what equation is used to relate stomatal conductance to CO2? This is relevant since it will affect the strength of this transpiration/gs effect.

Model description:
In line with some of the previous reviewers’ comments, I still found it a bit confusing to decipher which versions of the model and which developments are relevant in this study. Although it is the basis for r4999, this manuscript does not assess OCN (which is fine), but which developments mentioned in the Methods are in both versions of the model evaluated here? I am thinking in particular of the 4 changes listed at the top of page 4, the developments in 2.1.1 and 2.1.2. Perhaps a brief summary at the end of the model description section would help (and would also give a chance to introduce r3977 before the results section).

BNF: The approach for BNF in this study (using a single climatology of ET from a control run) does seem reasonable but how will it be handled for other applications of this model (such as being run in a coupled mode) – is there a method for calculating a climatology of ET as the simulation evolves, or will it always rely on the same climatology? (Page 5, lines 10-15)

Results and Discussion:
Page 18, Paragraphs from Line 20-32: Isn’t it possible that the biases in GPP cause the biases in LAI, rather than the other way around?

It was good to see a discussion of GPP might be so much lower in tropical Amazon and Indonesia in r4999 in the Discussion. However GPP biases also appear lower in high latitudes (the overestimation is removed) – is the reason for this improvement understood? Does it have to do with plants being unable to access N in frozen soils, or is there something else going on?

The explanation of the large effect of dynamic CN for C3 grasses has not really explained why they are so different: What is meant by “extreme” conditions which lead to the depletion of the labile pool of N. Does this occur during certain climatic events such as droughts or heat waves? Can anything more specific be said about why the pool becomes depleted at these sites but not at any of the others? (Page 21, Paragraph starting from Line 20)

Minor comments:
Page 14, Line 27-31: Should this be MSE or MSD? It is MSD in Eq. 13.

Table 2 is very helpful but reference it earlier, ie in Section 2.4.2

I think it’s relevant to point out earlier in the manuscript that ORCHIDEE with these CN developments are being used in the CMIP6 experiments. This increases the importance of understanding the large-scale effects of the CN interactions. Also, although not necessary I wonder if the model needs a name, could this be OCN2?? Referring to ORCHIDEE r4999 seems bulky for future reference, if this will now replace OCN in future model comparison projects.

Page 18 Lines 9-12 There is some repetition of information here.

Hide

ED: Publish subject to minor revisions (review by editor) (12 Aug 2019) by Gerd A. Folberth

AR by N. Vuichard on behalf of the Authors (30 Aug 2019) Author's response Manuscript

ED: Publish as is (09 Sep 2019) by Gerd A. Folberth

AR by N. Vuichard on behalf of the Authors (18 Sep 2019)

Short summary

In this research, we present a new version of the global terrestrial ecosystem model ORCHIDEE in which carbon and nitrogen cycles are coupled. We evaluate its skills at simulating primary production at 78 sites and at a global scale. Based on a set of additional simulations in which carbon and nitrogen cycles are coupled and uncoupled, we show that the functional responses of the model with carbon–nitrogen interactions better agree with our current understanding of photosynthesis.