Influence of Ozone and Drought on Tree Growth under Field Conditions in a 22 Year Time Series
Round 1
Reviewer 1 Report
The paper examined tree growth, basal area increment (BAI) and fructification severity of F. sylvatica and P. abies on several plots in Wester n Germany based on 22-years of data time series. The paper is written in excellent English, has proper citations and deals with extremely important topics of carbon uptake decline die to O3. Moreover, authors use POD1 index rather than classical AOT40, which is much more precise. Authors conclude that drought and O3 pollution has negative effect on those specimens.
Here are just minor suggestions:
line 90: shouldn´t GR be in W m-2?
2.2.3: PODY was calculated from concentration measurement or from eddy covariance flux measurement? That should be stated more clearly in the text. What is the comparison and uncertainties of calculation of PODY based on O3 concentration and real-world measurements based on eddy covariance flux measurements?
line 342: see paper 10.17221/129/2019-JFS showing reduced O3 flux during severe drought conditions due to stomatal closure
line 371: paper 10.3832/ifor2805-011 shows significant reduction of carbon uptake in real-world conditions relative to O3 presence before preindustrial revolution on Norway spruce middle European site. You might include this into your discussion.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear authors,
After reading your manuscript I came with some comments that I believe would improve the content of the manuscript.
Section 2.2.4, lines 147-150: From my point of view, it does not fit in the methodology, is more like an introduction sentence, belonging to the introduction section. To me it does not seem related to purely methodological section. I suggest deleting it or move.
Figure 1 & 4: Would it be possible to increase the quality of the images? They seem to be a little bit blurry
Figure 2: You could merge figure 2 and table 4, including the trend per specie, the growth in dots and the function aside. You would get rid of a table, and it would make figure 2 more informative.
Figure 3: I suggest displaying water deficit in the same graph as fructification since you mentioned they might be related. It would help to better picture its relationship visually.
Figure 4: In the methodology section global radiation was introduced as GR and here it is expressed as G. Same in line 254. Why sometimes you use the initials and in other moments the whole name? Example: line 259 with BAI and in the figure 4 Basal area index. Please, choose an abbreviation the first time you introduce a variable and be consistent with it throughout the paper. Also, I would recommend displaying the % explained by each axis in the figure.
Line 259: I do not agree when you say that POD1 and O3 concentration are related in the PCA. I would rather say they are closer to orthogonality, which is associated with independency.
Could you display the results of the RF model somewhere? It would help the readers to understand the direction of the relations on top of its importance that you are already showing in the figure 6.
Line 320-372: This paragraph confuses me a little. It is a condensed part of introduction, objectives. I don’t think this is necessary and you can go directly to the point and say what you want to say about your study.
Line 333: This is redundant, this sentence already appears in the result section. If it would make sense if you would go further on it but otherwise, I don’t think it is necessary here.
Line 407: Typo in individual.
Conclusion: Why are you talking about beetles here? Your study isn’t about beetles, even they intersect with your study. I think here you should express the bullet points of your study in a concise way. The rambling about beetles can have its place in the discussion section.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
