Net Ecosystem Exchanges of Spruce Forest Carbon Dioxide Fluxes in Two Consecutive Years in Qilian Mountains
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors,
I read carefully the manuscript entitled "Net ecosystem exchanges of spruce forest carbon dioxide fluxes in two consecutive years in Qilian Mountains" concerning the measurement of CO2 fluxes using tower-based eddy covariance method.
In my opinion the topic is of great relevance for the readers of Applied Sciences. However the manuscript is not ready for publication in the current form.
I include my detailed comments in the annotated file .pdf
Best Regards
Comments for author File: 
Comments.pdf
The English language is written in a very difficult form and must be improved. Please edit the text by a native english speaker.
Author Response
Dear editor
We agree with all the review opinion, and we modified all the manuscript one by one. Furthermore, we greatly thanks to this revision.
Sincerely
Review 1
- Line 31, For improving readability I would suggest using the same unit Pg.
Done. in Line 31, “0.18 Pg.”
- Line 49, Full stop here.
Done in Line 49, kPa was changed to “kilopascal”.
- Line 64, “Sustain”.
Done, we changed “hypothesis” to “sustain”.
- Line 69, I would suggest to include a figure with the study area and its collocation in the region.
Done in line 78-89, both Figure 1 and Table 1 were added
- Line 93-95, Please, all scientific names in italic
Done.
- Line 96, Please find a proper title for this section.
Done in line96, it was changed to “Data measurement”.
- Line 97, “... discusses data...”
Done. “This manuscript discusses data of forest CO2 flux”.
- Line 98-99, The sampling method should be concisely discussed in this section. This paper needs to be self-sustained.
Done, Line 98-99, “Integrated CO2 was automatically measured by open-path eddy covariance (CS106 Vaisala, USA) every half-hour, then we calculated daily average NEE flux”.
- The acquisition method needs a complete description in line 99-102.
Done, we added “The sampling frequency is 10 Hz, and the average 30-minute flux data was collected and stored in TOB3 format.” in line 102-103.
- Statistical analysis, “This section must be improved
This section was rewritten as “Half hour CO2 flux (NEE) and meteorological sensors data (daily sensible heat flux, latent heat flux, vapor pressure deficit, precipitation, air temperature) were calculated by “tapply” function as daily data in R statistics (4.3.0 version). Drive factors of three climate factors (latent heat flux, precipitation, air temperature) on NEE and vapor pressure deficit were analyzed by structural equation model using “piecewiseSEM” package. Figure 1was drawn in Arcgis 10.4 and other three figures were carried out in R statistics. “
- I can't see figure 2 and 3 in this version of the manuscript in line 114 and 134.
We added figure 2 and 3 in line 129-130 and 151.
- “A structural equation model was well formulated” Where this model was formulated?
Done, this structural equation model was well formulated in Figure 4 in line 176.
- See previous comment in Figure 4
We added figure 4 in line 176-180.
- Why R2 =0.32 is a good correlation? In comparison to what!
“Additionally, VPD was driven by air temperature and precipitation, the direct effect coefficients were 0.778 and -0.401, and both factors were extremely significant”. These were because of the direct effects of air temperature and precipitation on VPD were extremely significant in Figure 4 with 0.778 and -0.401(P<0.001). Thus, we changed it to “the direct effect coefficients were 0.778 and -0.401 (P<0.001), and both factors were extremely significant (R2 = 0.32).”
- Line 204 and 205, this statement is not supported by data shown in the manuscript
Done, in line 204, “sink approximately 591.51 (-617.96 and -565.06 in 2021 and 2022) g C m-2 on the northwest Tibetan Plateau.”
- Line 206, these changed to “those”.
Done.
- Line 215-217, “These results indicated that both drought and warming significantly depressed forest carbon sink in Qilian Mountain spruce forest ecosystem, rather than latent heat flux and precipitation.” This statement is not supported by data reported in this paper.
Done, we added “figure 4”.
- “In this study, average air temperature negatively regulated spruce forest NEE, the direct and indirect effect coefficients were −0.209 and −0.180, respectively.”, Is this a hypothesis of the Authors? There is no evidence of this statement throughout the manuscript.
Done, we added “figure 4”, −0.209 was the indirect effect coefficient, −0.180 was indirect effect coefficients by calculation.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript submitted for review contains a continuation of research conducted in spruce forests in the Qilian Mountains (China). Previous research on NEE was published by the authors in 2022 in the journal Biochemical Systematics and Ecology titled “Net ecosystem exchange of carbon dioxide fluxes and its driving mechanism in the forests on the Tibetan Plateau”(https://doi.org/10.1016/j.bse.2022.104451).
As indicated above, the authors have addressed this issue previously. In this respect, the work is not original. However, the experiment performed provides new data. Additional data obtained from November 2021 to December 31, 2022 were included in the analysis.
Detailed comments:
1. Haven't these hypotheses already been verified in previous studies (https://doi.org/10.1016/j.bse.2022.104451)?
2. The authors refer to figures (1-4) that were not included in the manuscript submitted for review (Page 2: 1and 22 lines from below; Page 3: 4, 10 and 14 lines from the top)
3. The authors refer to table 1, which they did not include in the manuscript (Page 2: 19 line from below).
4. Why is there no comparison with previous results from this area (Tibetan Plateau [10]) in the discussion? I assume that this manuscript contains original results that have not been published before and can be compared with previously published ones.
5. Conclusions: Specifically how and where these results can be used. Furthermore, please consider that the conclusion is intended to help the reader understand why your research should matter to them. A conclusion is not merely a summary of the main results but a synthesis of key points and where you recommend new areas for future research.
Technical note:
1. There are no numbered lines in the manuscript, which contributed significantly to the difficulty of the review.
2. References not prepared in accordance with the requirements journal Applied Sciences Applied Sciences | Instructions for Authors (mdpi.com)
Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range.
Comments for author File: Comments.pdf
Author Response
Dear editor and reviewers,
We agree with all the review opinion, and we modified all the manuscript one by one. Furthermore, we greatly thanks to this revision.
Sincerely
The manuscript submitted for review contains a continuation of research conducted in spruce forests in the Qilian Mountains (China). Previous research on NEE was published by the authors in 2022 in the journal Biochemical Systematics and Ecology titled “Net ecosystem exchange of carbon dioxide fluxes and its driving mechanism in the forests on the Tibetan Plateau”(https://doi.org/10.1016/j.bse.2022.104451).
As indicated above, the authors have addressed this issue previously. In this respect, the work is not original. However, the experiment performed provides new data. Additional data obtained from November 2021 to December 31, 2022 were included in the analysis.
Done, in this study, we compared NEE variation in two consecutive years (From 1th January 2021 to 31th December 2022, we discovered that Qilian Mountain spruce forests were robust carbon sink approximately 591.51 (-617.96 and -565.06 in 2021 and 2022) g C m-2 on the northwest Tibetan Plateau. Furthermore, Both VPD and average air temperature significantly decreased carbon sink function, but both latent heat flux precipitation weakly increased carbon sink. VPD was remarkably determined by air temperature and precipitation, with positive and negative direct effect coefficients.
In former paper, “The annual NEE flux was a robust carbon sink of 545.99 g C m−2 from November 2021 to December 31, 2022. Forest NEE was significantly driven by latent heat flux, net radiation, air temperature, and precipitation”.
To sum up, through two consecutive years research, out results were more robust on forest carbon sink. Furthermore, we revealed the main document driven factors, this would to predict change trend of future carbon sink.
Detailed comments:
- Haven't these hypotheses already been verified in previous studies (https://doi.org/10.1016/j.bse.2022.104451)?
Done, the above description, these hypotheses of driven factors were not the same. In this study, “we sustain that NEE was weak in 2022 compared with that in 2021 because of higher air temperature in 2022.” previous studies sustain one-year climate data, that hypotheses can not be verified.
- The authors refer to figures (1-4) that were not included in the manuscript submitted for review (Page 2: 1and 22 lines from below; Page 3: 4, 10 and 14 lines from the top)
Done in line 78-89, line 129-130 and 151, 176-180.
- The authors refer to table 1, which they did not include in the manuscript (Page 2: 19 line from below).
Done in line 95.
- Why is there no comparison with previous results from this area (Tibetan Plateau [10]) in the discussion? I assume that this manuscript contains original results that have not been published before and can be compared with previously published ones.
Done, “the annual NEE flux was a robust carbon sink of 545.99 g C m−2 from November 2021 to December 31, 2022” (Tibetan Plateau [10]). In this study, from 1th January 2021 to 31th December 2022, we discovered that Qilian Mountain spruce forests were robust carbon sink approximately 591.51 (-617.96 and -565.06 in 2021 and 2022) g C m-2 on the northwest Tibetan Plateau. In the introduction, we written “Annual NEE flux of spruce forest was a robust carbon sink of 545.99 g C m-2 on the northeast Tibetan Plateau [10]”. In this time, we also added “This carbon sink capacity was higher than 545.99 g C m-2 in annual study [10], in the discussion”.
- Conclusions: Specifically how and where these results can be used. Furthermore, please consider that the conclusion is intended to help the reader understand why your research should matter to them. A conclusion is not merely a summary of the main results but a synthesis of key points and where you recommend new areas for future research.
Done, line 248-250, we added “Our results would help to accurate evaluate carbon sink capacity, and predict its variation trend of spruce forests in Qilian Mountain.“
Technical note:
- There are no numbered lines in the manuscript, which contributed significantly to the difficulty of the review.
Done, all numbered lines were added.
- References not prepared in accordance with the requirements journal Applied Sciences Applied Sciences | Instructions for Authors (mdpi.com):
Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range.
Done, all references were revised to satisfy the requirements journal Applied Sciences.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have addressed my major concerns properly, and i consdider the current version suitable for publication. Below are some technical notes.
Technical notes.
1. Figure 1 should be corrected. The legend and axis descriptions are illegible.
2. Line 95. Remove the italic
3. Figure 2 ,3, 4. Improve the quality of these drawings. In this form, they resemble copies or scans.
