Variation of Stem CO2 Efflux and Estimation of Its Contribution to the Ecosystem Respiration in an Even-Aged Pure Rubber Plantation of Hainan Island
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsGeneral comment
This study is interesting because it measured stem respiration directly in a rubber tree plantation, where data is scarce. The data is important for examining gas exchange in forest ecosystem.
Specific comments
1. L.52-55 For example, high concentrations of Co2 ....transported upward by xylem sap flow [6,23]
It might be better to make the sentence understandable without reading the references.
2. L.74-76　The net ecosystem carbon exchange (NEE) of... with different intensity[37].
It might be better to make the sentence understandable without reading the references.
3. L.105-106.　The mean diameter at breast height of trees is around 21 cm and the mean canopy height is about 16m.
It might be better to mention the age of the trees. You should refer to Table1 "....and the mean canopy height is about 16m (Table 1)."
4. L,136　Reco data
What is the Reco data?
5. L.140-141　All measurements were carried out in the morning
The measurement interval should be mentioned.
6. L.141　the effect of diurnal variation on flux.
What is the effect, for example?
7.L.159 r is half of the stem vasal diameter (m)
Is the r measured at DBH？
8. L.162　Es
The explanation and unit of Es should be written.
9. L.169 by multiplying Ev and V
In equation (4), Ea and 2πd/πd2 are multiplied, and the process of calculation cannot be understood.
10. Table 1　Tapped years
What are Tapped years?
11. Appendix A　
Units should also be listed for clarity.
Author Response
Please see the attachment "Response to reviewer 1"
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThere are some issues that need to be improved.
1. The Abstract should be more clear and more objective.
(1) There are too many English abbreviations in the abstract, which affects the readability of the article and makes the readers more confused. In fact, several abbreviations are unnecessary.
(2) In these abbreviations, authors do not introduce what is the relationship between Es and Ea, Ev, which makes people more confused.
(3) Among these abbreviations, authors do not describe what Es3.0, Es4.5 and Es1.5 are.
(4) From the following content, this paper belongs to the experimental case article, so the typicality or particularity of the research area is also very important. Therefore, it is necessary to add information about China, Hainan Province or tropical areas of China in the title, abstract and keywords. Consider whether you need to fine-tune the title of the article and add the response to the abstract.
2. The statements of the Introduction are with slightly poor logics, and the research purposes, research ideas and research innovation are not clear.
(1) In Line 47-50, Please consider whether there is any semantic contradiction between these two sentences (“However, whether…conifer species [11-14].”).
(2) Ea and Ev are two important methods used in this paper, but there is no review of the relevant methods in the introduction.
(3) The last sentence of the third paragraph is more abrupt and not logically coherent with the preceding sentences. What is the relationship between NEE and the previous content？
(4) In addition, in the third and fourth paragraphs，why rubber plantations are chosen to study Es instead of other tree species, why Hainan rubber trees are chosen to study are not explained in this paper.
(5) At present, the fourth paragraph may have to be reorganized and revised.
In conclusion, the current research review is obviously insufficient. What is the current research progress internationally and in China, what is the difference between the research and previous studies, and what are the specific reasons and advantages of choosing Hainan as a case need to be elaborated in depth. In Introduction, please states explicitly the research thoughts and research innovation. To solve the topic problem, which methods have been adopted and what is the differences and advantages of your method compared with other methods?
3. Materials.
(1) Are these sentence grammatically correct in Line 91-92，“The location is dominated by the monsoon climate” and Line 100-101，“The rubber trees (clone Reyan 73397 and PR107) were planted in an area across 5 hectares” ？Please check.
(2) In Line 124-126, what are the open-sky A value, logged 35–40 values, and Z-shaped location, and how do they relate to the text that follows?
(3) I strongly suggest that the position of Hainan Province in China，as well as the location and general situation of rubber growing areas and sample plots in Hainan Province should be drawn in this part. This background information is unfamiliar to foreign readers and is important for the integrity and rationality of the article structure.
(4) In line 132，what do you mean by “filled half-hourly gaps”？
(5) In line 133，NEE here should be written as the full name.
(6) In line 176，why do you multiplying 476？
4. Results.
(1) I see that the data of a and c in Figure 2 are missing in the time series. Do you need to make supplementary explanations in the previous Materials and Methods section？
(2) In 3.4, Ea was significantly positively related to Ta and LAI in Line 252 and was minimally affected by Ta and Ts, as reflected by low correlation values in Line 254. These two sentences are semantically contradictory and do not agree with the results in Table 2.
(3) Figure 5 needs to be improved, and the position of formulas in different sub-graphs should be unified.
6. The statements of Discussion is with slightly poor logics.
(1) In 4.1, the influence of climate factors on the seasonal variation of ES is also very important. Please check whether the content of this part is partial.
(2) In 325，you say “However, Ea had distinct hysteresis of LAI and VWC”，where does this conclusion come from at Section 3.
(3) In line 336，DBH here should be written as the full name.
(4) Compared with previous studies, what are the similarities and differences of this study, how to reflect the contribution and value of this study, and what are the shortcomings and prospects of this study? These elements are currently missing in the discussion.
6. The statements of Conclusions does not conform to the writing standards of academic papers and needs to be rewritten.
The current conclusion is written like a discussion. The research content and results of this paper need to be expressed logically and clearly.
Comments on the Quality of English LanguageYou need to read the whole text. Minor editing of English language required.
Author Response
Please see the attachment "Response to reviewer 2"
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsTitle
Title can be rewritten as " Variation of stem CO2 efflux and its contribution to the ecosystem respiration in a rubber plantation"
Abstract
#There are some grammatical errors and repetition of results.
# Keywords are not appropriate.
Introduction
# Revised the whole manuscript to avoid grammatical mistakes.
# Justification of the study is missing.
# Objective 1 is ambiguous.
Methods
# In subsection 2.4 authors mentioned that height of platform for canopy observation is 14m but mean canopy height is 16m (see subsection 2.1). Is it possible?
# Authors are advised to use passive sentences in the methods section.
# Why and how four trees were selected?
Results
# Result section should be more clear for easy understanding to the readers.
# Table 2 is somehow misleading as it has no reflection in the text.
# This section is not suitable for any recommendation.
# What did authors mean by Figure 6(b).
Discussion and Conclusion
Authors are advised to improve discussion and conclusion sections based on research objectives and findings.
Comments on the Quality of English LanguageAuthors are advised to revise the whole manuscript to avoid grammatical errors.
Author Response
Please see the attachment "Response to reviewer 3"
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsWe can see the revised Manuscript have been a more appropriate and meaningful topic. However, some of the problems I mentioned last time have not been modified by the author.
There are some issues that need to be improved.
(1) Maybe the word "estimating" in the title needs to be dropped.
(2) As I said before, in fact, several abbreviations are unnecessary in Abstract, such as Es3.0 in Line 21, Es4.5 and Es1.5 in Line 22.
(3) Would it be more appropriate to change " area-based Ea and volume-based Ev " to " area-based method (Ea)and volume-based method (Ev)" in Line 24?
(4) As I said before, please consider whether there is any semantic contradiction between these two sentences (“However, due to…conifer species [11-14].”).
(5) There are still many grammatical errors and sentences that do not conform to English expression habits.
As I said before, the sentence, " The location is dominated by the monsoon climate "，contains grammatical errors. The word, " location " is actually misnomer or improper use of words. You didn't correct it.
The sentence, " The rubber trees (PR107) were planted in an area across 5 hectares in 2001 ", didn't accord with the English idiomatic expressions.
(6) Figure 1 must be further refined. Perhaps you can try using software such as ArcGIS for mapping. In addition, sub-maps can be set up, with one sub-map clearly showing the location of Hainan Island in the whole Chinese mainland, and the other sub-map clearly showing the distribution of Danzhou and your observing site in Hainan Island.
(7) As I said before, the sentence, " We collected three open-sky A value outside the forest and logged 35–40 B values beneath the forest canopy to inverted the LAI value "，is still without the necessary interpretation.
(8) As I said before, Figure 6 needs to be improved, and the position of formulas in different sub-graphs should be unified at the same height.
(9) As I said before, the current conclusion is written like a discussion. The research content and results of this paper need to be expressed logically and clearly.
Comments on the Quality of English LanguageAt the same time, I found that there was no improvement in English expression between this edition and the previous edition, so I suggest that this paper needs to make great improvements in English expression.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
