Relative Humidity, Soil Phosphorus, and Stand Structure Diversity Determine Aboveground Biomass along the Elevation Gradient in Various Forest Ecosystems of Pakistan

Round 1

Reviewer 1 Report

Above-ground biomass is one of the final parameters of forest ecosystem, which is of great significance to the study of forest productivity and carbon sink function. Therefore, this study has important theoretical and practical significance. Based on the analysis of first-hand data from field investigation and laboratory analyses, this study draws valuable conclusions, therefore, it is a high-quality academic paper. But at the same time there are some areas that can be improved. The areas to be improved are as follows:

The overall quality of this study is good, and valuable scientific conclusions are drawn based on field investigation and laboratory analysis data. It is a high-quality academic paper, but there are also some problems in this paper:（1）The biggest factors influencing the above-ground biomass of forest are the age of the stand and the dominant tree species. This study only said that the study stand was a natural forest, which only explained the origin of the experimental stand, whether they were original natural forest or some natural secondary forest, how the structure of the experimental stand age group, whether age group of the same type of stand is the same? Are the dominant species the same, and what are the dominant species in each stand type? These are all not written down, please write them down in detail, because quantity alone is not convincing.

（2）Climate impacts are generally studied at large scales. Is it scientific to study climate impacts on above-ground forest biomass at small scales within a maximum distance of 40 km? Especially where the elevation gradient does not change much, it is not suitable for such a study.

（3）Is it reasonable to use world meteorological data directly to study the effects of climate on above-ground forest biomass in the 800-40000m range? How different is the relative humidity from the actual relative humidity of the stand? Given the small-scale nature of this study, taking into account the effects of elevation, it is recommended that climate be changed to topography to study the effects of soil, topography, and stand structure on aboveground organisms.

(4) Soil organic matter content, nitrogen content, soil thickness and pH value are generally used to characterize soil properties. Why is soil phosphorus content used to characterize soil properties in this paper and what is the basis? Please elaborate on this.

（5）Some conclusions may not be quite correct, such as the authors' suggestion that aboveground biomass decreases with altitude because soil fertility decreases and wind pressure increases with altitude. Although it is consistent with previous studies in other places, while, it does not provide necessary literature support. The increase of forest aboveground biomass with increasing altitude may be related to the decrease of human disturbance with increasing altitude. Please give reasonable explanations for such conclusions.

(6) For some other details, e.g., the units in the figure are not correct, the significant digits after the decimal point need to be consistent, and the tenses should be consistent.

Based on the above problems, I personally think this paper needs to be carefully revised before it can be accepted for publication.

Comments for author File: Comments.pdf

Author Response

Reviewer # 1

Above-ground biomass is one of the final parameters of forest ecosystem, which is of great significance to the study of forest productivity and carbon sink function. Therefore, this study has important theoretical and practical significance. Based on the analysis of first-hand data from field investigation and laboratory analyses, this study draws valuable conclusions, therefore, it is a high-quality academic paper. But at the same time there are some areas that can be improved. The areas to be improved are as follows:

Response: Thank you for your thoughtful comment. It's great to hear that you recognize the significance of above-ground biomass in studying forest productivity and carbon sink function and that you find this study important theoretical and practical significance. We agree that the first-hand data from field investigation and laboratory analyses provide a strong foundation for the valuable conclusions drawn in this paper. We appreciate your suggestions for areas that can be improved, and we have considered them during revision and future research as well. We have tried our best to improve our work and appreciate your constructive feedback. Thank you again for your thoughtful input.

The overall quality of this study is good, and valuable scientific conclusions are drawn based on field investigation and laboratory analysis data. It is a high-quality academic paper, but there are also some problems in this paper:（1）The biggest factors influencing the above-ground biomass of forest are the age of the stand and the dominant tree species. This study only said that the study stand was a natural forest, which only explained the origin of the experimental stand, whether they were original natural forest or some natural secondary forest, how the structure of the experimental stand age group, whether age group of the same type of stand is the same? Are the dominant species the same, and what are the dominant species in each stand type? These are all not written down, please write them down in detail, because quantity alone is not convincing.

Response: We have added table 1, covering all the information, including forest types, location, climatic conditions, stand type, and main or dominant species.

（2）Climate impacts are generally studied at large scales. Is it scientific to study climate impacts on above-ground forest biomass at small scales within a maximum distance of 40 km? Especially where the elevation gradient does not change much, it is not suitable for such a study.

Response: The current study was conducted in different forest types from sub-tropical to temperate forest ecosystems, including both dry and moist conditions, covering a large area i.e., from 50 to 2700 meters above sea level. Please read table 1, which comprehends all the relevant information.  

（3）Is it reasonable to use world meteorological data directly to study the effects of climate on above-ground forest biomass in the 800-40000m ranges? How different is the relative humidity from the actual relative humidity of the stand? Given the small-scale nature of this study, taking into account the effects of elevation, it is recommended that climate be changed to topography to study the effects of soil, topography, and stand structure on aboveground organisms.

Response: Thank you for your comment and interest in our study. After careful consideration, we have decided that using world meteorological data directly to study the effects of climate on above ground forest biomass in the 800-40000m ranges is a reasonable approach for our study objectives. We understand that relative humidity may differ from the actual relative humidity of the stand, but we believe that using the available meteorological data will still provide useful insights. Regarding your suggestion to change our focus to topography and study the effects of soil, topography, and stand structure on aboveground organisms, we appreciate your input, but our research questions are focused on the effects of climate on above-ground forest biomass. Therefore, we will continue to use meteorological data for our study.

(4) Soil organic matter content, nitrogen content, soil thickness and pH value are generally used to characterize soil properties. Why soil phosphorus is content used to characterize soil properties in this paper and what is the basis? Please elaborate on this.

Response: We have included soil phosphorus content as one of the soil properties to characterize the soil because phosphorus is an essential nutrient for plant growth and is a key component of many plant molecules, including nucleic acids and ATP. It is also a primary limiting nutrient in many ecosystems, particularly in tropical and subtropical regions where the soil is often phosphorus deficient. Therefore, understanding the phosphorus status of the soil is important for understanding plant growth and ecosystem processes. We have examined the relationship between soil phosphorus content and above-ground biomass in tropical forests. We found that soil phosphorus content was a significant predictor of above-ground biomass, suggesting that phosphorus availability may limit plant growth in this ecosystem. The basis for including soil phosphorus content as a soil property to characterize the soil was its importance as a limiting nutrient for plant growth, particularly in tropical regions. While soil organic matter content, nitrogen content, soil thickness, and pH value are commonly used to characterize soil properties, we believe that soil phosphorus content is also a critical factor to consider in assessing the health and productivity of an ecosystem.

（5）Some conclusions may not be quite correct, such as the authors' suggestion that aboveground biomass decreases with altitude because soil fertility decreases and wind pressure increases with altitude. Although it is consistent with previous studies in other places, while, it does not provide necessary literature support. The increase of forest aboveground biomass with increasing altitude may be related to the decrease of human disturbance with increasing altitude. Please give reasonable explanations for such conclusions.

Response: We have revised the conclusion section in light of the above suggestion and the core findings of the study.

(6) For some other details, e.g., the units in the figure are not correct, the significant digits after the decimal point need to be consistent, and the tenses should be consistent.

Response: We appreciate your input regarding the units, significant digits, and tenses in our figures and text. We agree with you that accuracy and consistency in reporting these details are essential for ensuring the quality of our research. We have revised our figures and text to ensure that all units are correct and consistent, significant digits are consistent and appropriate, and tenses are consistent throughout the manuscript.

Reviewer 2 Report

This work deals with the effect of climate (through a single parameter which is humidity), soil (through a single parameter which is phosphorus content), latitude, and species richness on the production of aboveground biomass of 5 different forests.

I commend the authors on this giant work, as they evaluated 15,260 tree individuals covering 104 plant species across 200 forest plots.

I think that the results are exciting and they will add valuable knowledge for forestry.

Here are some remarks that can improve the quality of this work

1- it exists some ambiguities in the title because the soil studies cover many fields such as soil texture and structure, mineral and organic composition, and humidity, ... However, the authors studied only the effect of phosphorus I propose slowly modifying the title to be more clear. The same comment for the climate as it was represented only by humidity. 

2- the strongness of the paper is the application of modelization in data treatments however we dont observe any values of measured parameters. I propose to add some tables (as annexes documents for example) to show some values such as phosphorus level, and humidity rate, ...

3- in the abstract, in the sentence "Coefficient Variation of DBH (CVD)": please add the significance of the abbreviation DBH.

4- Structure problem in the last paragraph of abstract : I don't understand how a favorable climate reduces aboveground biomass. You can split  this paragraph into two sentences. 

 

Author Response

Reviewer # 2

This work deals with the effect of climate (through a single parameter which is humidity), soil (through a single parameter which is phosphorus content), latitude, and species richness on the production of aboveground biomass of 5 different forests. I commend the authors on this giant work, as they evaluated 15,260 tree individuals covering 104 plant species across 200 forest plots. I think that the results are exciting and they will add valuable knowledge for forestry. Here are some remarks that can improve the quality of this work

Response: Thank you for taking the time to review our research and for your positive feedback. We appreciate your kind words and recognition of our effort in this work.

1- it exists some ambiguities in the title because the soil studies cover many fields such as soil texture and structure, mineral and organic composition, and humidity, ... However, the authors studied only the effect of phosphorus I propose slowly modifying the title to be more clear. The same comment for the climate as it was represented only by humidity. 

Response: we have revised the title to reflect the focus of our study more accurately. We hope this change clarifies our research aims and provides a more accurate representation of our findings.

2- the strongness of the paper is the application of modelization in data treatments however we dont observe any values of measured parameters. I propose to add some tables (as annexes documents for example) to show some values such as phosphorus level, and humidity rate, ...

Response: We added an additional table to the revised version of manuscript, which presents the values of soil phosphorus content and humidity rate for each forest plot studied. We hope that this table provides a useful reference for readers interested in the specific values of these parameters.

 

3- in the abstract, in the sentence "Coefficient Variation of DBH (CVD)": please add the significance of the abbreviation DBH.

Response: It has been revised accordingly i.e., Coefficient of Variation of Diameter at breast height (CVD). Whole of the manuscript has been check for such types of mistakes.

4- Structure problem in the last paragraph of abstract : I don't understand how a favorable climate reduces aboveground biomass. You can split this paragraph into two sentences.

Response: These phenomena has been replaced with more relevant conclusion in the revised version of manuscript. 

Reviewer 3 Report

see an attachment

Comments for author File: Comments.pdf

Author Response

Reviewer # 3

The research topic of the authors is relevant. The scope of work is large. However, there are
some comments on the presented material.

Response: Thank you for reviewing our research paper and your feedback. We appreciate your recognition of the relevance and scope of our work.

Title. Maybe, it is necessary to point to the region in the title?

Response: After careful consideration, we agree that adding the region to the title may enhance the clarity and specificity of our study. Therefore, we have revised the title and included the studied region. It can read as, “Relative Humidity, Soil phosphorus, and Stand Structure Di-versity affect Aboveground Biomass along Elevation Gradients in the Forest Ecosystems of Pakistan”.

Keywords. Keywords are necessary for search systems, therefore they must not be doubled
in the Title.

Response: We have revised and edited the keywords accordingly. It can be read as, “Forest inventory; Environmental factors; stand structure complexity; regional scale; Structural equation modeling”.

Abstract is too long: The abstract should be a total of about 200 words maximum.

Response: We have condensed the abstract section to the recommended length.

Introduction. SSC must be explained at first mention.

Response: All the acronyms has been mentioned in full form where first time used. SSC means “stand structure complexity”.

“104 plant species” are mentioned In Abstract and “104 tree species” on the page 3, “All plant individuals with a ≥ 1 cm diameter at breast height (DBH) were noted within each plot.... All woody plants present in the plots were identified (page 5).

Response: We have revised the relevant sections of the paper and corrected the statement in abstract to match the language used throughout the rest of the paper. Specifically, we recorded all plant individuals with a ≥ 1 cm DBH within each plot and identified with help of expert taxonomist. This includes a total of 104 tree species as stated.

M&M.
In Figure 2, you need to indicate the forest types with numbers or letters and explain them in
the captions under the figure. The text of 2.1 should mainly be presented in the table, indicating the name of forest type (full and short), latitude, longitude, altitude, pure or mixed forest, as well as relevant references. It is advisable to mention at least the Latin names of the most common tree species.

Response: Thank you for your suggestion. We have revised Figure 2 to indicate the forest types with numbers and have included a caption explaining each forest type. We have also created a table 1 in section 2.1 that presents the name of each forest type, elevation, stand type, mean annual temperature, mean annual precipitation, and main or dominat species of the studied forest types. We have included the Latin names of the most common tree species as well in the table 1.

M&M. 2.2. All data were classified into 5 forest types and two species groups.
It is indicated that pure pine forests were in TTPPF (dry? DTPPF?), but it is not indicated which type of forest had mixed stand composition. It is also not indicated whether these were pine and other coniferous or coniferous and deciduous tree species. If mixed forests were taken in MTMF, and pure forests in DTPPF, then it is not known whether the results of calculations were affected by relative humidity or tree species composition.
GPS (geographical positioning system) and elevation values were also noted for each plot on
the x-axis. – why on the x-axis and where are such Figures?

Response: We have revised the text to provide more clarity on the specific forest types and their composition. We have provided a detail table 1 that describes all the forest types. We have also noted the elevation on x-axis for the entire 200 plot and consider the x-axis as a standard point.

 

You used Shannon's species diversity index Shannon’s species index was used in each
plot (page 6). Is it the same index?

Response: Yes, these are the same and this is Shannon diversity index. We have corrected this mistake in the revised version of manuscript.

For each tree's AGB estimation, pantropical allometric equations were used AGB = 0.0673 (ρ
dbh ×h) 20.976, based on tree height, dbh, and species wood density (Chave et al., 2014) (was the wood density the same for all tree species?)

Response:  We have measured wood density for all tree species included in our study and found some variation in wood density between species.

2.3. fisher statistic. – must be Fisher statistics.
Explain, how did you calculate the standardized coefficient, and what software was used for
Figures building.

Response:  Fisher statistics has been rewrite as suggested. The standardized coefficient was calculated in R statistical software.

3. 
   Results. Comments should be added to the figures - decoding of variables and coefficients.
   In the text, it is necessary to describe the revealed features and patterns in accordance with the tasks of the research.

Response: We have revised our figures and added appropriate labels and captions to decode the variables and coefficients. We have also updated the text to better describe the patterns and features observed in our research in accordance with the tasks of the study. We hope these revisions will address your concerns and improve the clarity of our work.

All Figures, Schemes and Tables should have a short explanatory title and caption.
If there are 5 figures in one Figure, they must be signed, for example, a), b), c), d), e)
In the text – (Fig. 3 a).

Response: We have revised our manuscript and added short explanatory titles and captions for all Figures, Schemes, and Tables. We have also labeled the sub-figures as suggested (e.g., Fig. 3a, 3b, etc.) to make it clear which specific part of the Figure is being referred to in the text.

Figures 3–6 are without titles... References to the figure number must be added to the text...

Response: Titles has been added to each figures in the revised version of manuscript. All the figures and tables have been cited in the relevant place in the main document as well.  

The conclusions are mostly logical, but the text needs to be edited for better understanding.
I would like to notice that the studied factors affect not only the biomass, but also the resistance
to various damage factors, incl. biotic. For example, biomass in wet conditions may be greater than in dry conditions, but trees are infested with wood-destroying fungi, which may increase biodiversity but be unfavorable for forestry.

Response: We acknowledge that the studied factors may also affect the resistance to various damage factors, our research question was specifically focused on the impact of soil and climate variables on aboveground biomass.

References. Grace et al., 2016; Lefcheck, 2016 and Hoyle, 2012 are absent from the reference
list.
Two papers of Grubb, P. J. (1977) must be marked as 1977a and 1977b or put all sources in
order of appearance in the text
All citations of web-sites must be included in the reference list.
Citation. see the rules https://www.mdpi.com/journal/sustainability/instructions#figures
In the text, reference numbers should be placed in square brackets [ ], and placed before the
punctuation; for example [1], [1–3] or [1,3].

Response: All the references has been checked  and edited according to journal requirements.

Round 2

Reviewer 1 Report

    The overall quality of this paper is very good, but there are still two outstanding problems: (1) The above ground biomass calculation model. It may not be appropriate to use the above ground biomass model of tropical trees to calculate the above ground biomass of non-tropical trees. Please give a reasonable explanation? (2) As mentioned last time, it is obviously inappropriate to use the meteorological data of the global meteorological database to study the impact of the meteorological factors on the above-ground biomass of a small scale less than 1600 square kilometers, because the global meteorological data of a city may not have a meteorological station, and it is acceptable to use this meteorological data to carry out large-scale research. But conducting small-scale studies is unacceptable. If you want to do meteorological effects on aboveground biomass, you can do it based on scientifically valid data. It is recommended that a final study of meteorological effects on above-ground biomass of all plots be carried out, which is barely acceptable.

     Based on the above problems, I personally suggest that this paper should be carefully revised before being accepted and published.

 

Author Response

The overall quality of this paper is very good, but there are still two outstanding problems:

Response: Thank you for your feedback on the paper. We appreciate your time and efforts towards improving our manuscript. We have addressed your comments to further improve the quality of the paper.

1. The above-ground biomass calculation model. It may not be appropriate to use the above-ground biomass model of tropical trees to calculate the above-ground biomass of non-tropical trees. Please give a reasonable explanation.

Response: We have given suitable equations for tropical and non-tropical tree AGB estimation in the revised version of the manuscript. It can be read as: “Pantropical allometric equations were used [AGB = 0.0673 (ρ dbh ×h) 20.976] for tropical forests, each tree's AGB estimation, based on tree height, diameter at breast height (dbh), and species wood density [42].

For Pines forest, we used the below equation;

Crown Biomass

W_C= 0.1377 (D)^1.4873  × (L) ^0.4052

W_S= 0.0600 (D) ^0.7934 ×^0.7934 (L)^1.8005

Total Biomass= W_C+W_S

 

2. As mentioned last time, it is obviously inappropriate to use the meteorological data of the global meteorological database to study the impact of the meteorological factors on the above-ground biomass of a small scale less than 1600 square kilometers, because the global meteorological data of a city may not have a meteorological station, and it is acceptable to use this meteorological data to carry out large-scale research. But conducting small-scale studies is unacceptable. If you want to do meteorological effects on aboveground biomass, you can do it based on scientifically valid data.It is recommended that a final study of meteorological effects on above-ground biomass of all plots be carried out, which is barely acceptable.

 

Response: It was a typographical mistake. We have taken relative humidity data using a digital humidity meter. It has been corrected in the revised version of the manuscript as well.

Reviewer 3 Report

The authors took into account the comments of the reviewer.

It seems to me that the abstract exceeds the recommended length (280 words instead of 200), but this is at the discretion of the editor.

The text needs to be rechecked: there are words with a capital letter in the middle of sentences, a lack of commas, etc.

Author Response

It seems to me that the abstract exceeds the recommended length (280 words instead of 200), but this is at the discretion of the editor.

Response: We have reduced the abstract section to below 200 words.

The text needs to be rechecked: there are words with a capital letter in the middle of sentences, a lack of commas, etc.

Response: The whole manuscript has been checked for such types of mistakes and typographic errors.

Round 3

Reviewer 1 Report

I hope the authors carefully check and proofread the manuscript, so as not to make some small mistakes. The Latin name of the manuscript is irregular. The Latin name should be written in its entirety name ((genus + specific epithet + Information about the named person)) when it appear first time, The genus name should be abbreviated when i reappear again. There are two Latin names for Prosopis glandulosa in the second row of the last column in Table 1. Are they the same species or different varieties? Please check. There is an extra "funding:" in Funding of the Supplementary Materials.

Author Response

Thanks for your comments and suggestions.

We have revised our manuscript  in light of your valuable comment. 

Many thanks