Ozone vegetation damage effects on gross primary productivity in the United States

Yue, X.; Unger, N.

doi:https://doi.org/10.5194/acp-14-9137-2014

Articles | Volume 14, issue 17

https://doi.org/10.5194/acp-14-9137-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-14-9137-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 14, issue 17

Research article

|

05 Sep 2014

Research article |

| 05 Sep 2014

Ozone vegetation damage effects on gross primary productivity in the United States

X. Yue and N. Unger

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Final revised paper (published on 05 Sep 2014)
Supplement to the final revised paper
Preprint (discussion started on 02 Dec 2013)

Interactive discussion

Status: closed

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

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- Supplement

RC C11422: 'review comments', Benjamin Felzer, 24 Jan 2014
- AC C13401: 'Responses_to_Benjamin_Felzer', X. Yue, 28 Apr 2014
RC C12699: 'Reviewer Comments for Yue & Unger', Anonymous Referee #2, 05 Mar 2014
- AC C13402: 'Responses_to_Reviewer_2', X. Yue, 28 Apr 2014

Peer-review completion

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

AR by Xu Yue on behalf of the Authors (28 Apr 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 May 2014) by Silvia Kloster

RR by Benjamin Felzer (20 May 2014)

Suggestions for revision or reasons for rejection

I find the authors have responded to all my concerns, with one minor exception.

The point I was trying to make in my comment below was not just the effect of including N-limitation, but also that including N deposition would more than likely offset the negative effects of ozone on GPP. All this requires is one additional sentence or so on their part to acknowledge this. I can provide one of my own references, though I am happy if they choose any reference (does not have be mine) that makes the point.

Felzer, B. S., Cronin, T., Reilly, J. M., Melillo, J. M. and Wang, X. 2007. Impacts of ozone on trees and crops. Comptes rendus Geosience. 339/11-12: 784-798.

12. There needs to be a discussion about the implications of not including nitrogen
deposition. Where high ozone levels exist, there are also likely high levels of N de-
position. So, while inclusion of ozone improves the model estimates (final paragraph
section 3.3), including nitrogen deposition would probably more than offset the ozone
effects. A separate issue to discuss in the final section is the implications of using a model
that does not account for effects of N-limitation on GPP. Is that the main reason why
GPP values are too large? Is the addition of ozone just correcting for this effect?

We understand that missing of nitrogen deposition may be a source of uncertainty in our
estimation of O3 vegetation damage. We discuss such limitation, as well as other factors,
in the revised paper as follows: “Interestingly, this mechanism would therefore provide a
way to improve the simulated GPP overestimates. That said, other studies have suggested
that the O3 damage effect is limited by carbon-nitrogen interactions (Ollinger et al., 2002; 5
Kvalevag and Myhre, 2013).” (1st
paragraph of section 4)

The GPP values are not always too large, as you may find that our predicted GPP is lower
than observations at some sites (Fig. 2). We did not calibrate the model for O3 damage
purpose, since we use almost the same parameters from the Community Land Model
(CLM). Most important, the O3 damage to vegetation is limited in U.S. due to the low
[O3]. The correlations are almost identical with and without O3 (Fig. S3)

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RR by Anonymous Referee #2 (21 Jun 2014)

Suggestions for revision or reasons for rejection

The authors have made considerable improvements to the paper and have addressed many of the reviewers’ concerns. The text is much clearer, with methodology and results more understandable and accurate. The analyses and results are discussed within the context of observations and other studies and seem reasonable. Here are a few additional comments, and these and other minor comments are annotated within the attached text:

1) What is a “distributed” simulation? Do you mean regional simulation? This terminology comes up throughout the text, and is not clear what is meant. If the simulations are regional, please change “distributed” to “regional”, or else include an explanation of what makes a simulation “distributed”.

2) You have included a great number of sensitivity analyses, but none test the sensitivity of the particular ozone parameterization used for each PFT. The Sitch (2007) approach is laden with potential problems, including that the parameterization is based on only a few species of plants, and was developed based on decreases in biomass rather than photosynthesis (which are not equivalent). Is it possible that results would show greater differences if different PFT parameters were used? This is key to your results and currently completely overlooked, so at least some discussion of this weakness should be included.

3) The figures are much cleaner, but 40 panels is still too many for the main body of the text. If you don’t want to average by pft, can you choose one representative panel for each pft (e.g. 5 panels total) and then include the others as supplemental? Also, for the bar charts, can you plot histograms of the X2 instead, and have parts of each bar/bin color-coded for the PFT type?

Referee Report: PDF

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ED: Reconsider after major revisions (10 Jul 2014) by Silvia Kloster

AR by Xu Yue on behalf of the Authors (14 Jul 2014) Author's response Manuscript

ED: Publish as is (04 Aug 2014) by Silvia Kloster

AR by Xu Yue on behalf of the Authors (04 Aug 2014)

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