Litterfall and Accumulated Nutrients in Pinus taeda Plantation and Native Forest in Southern Brazil

Round 1

Reviewer 1 Report

This manuscript follows the litterfall types, weights, and nutrient contents of two forest types in Brazil.  I still believe that explaining the nutrient concentrations of litter do not necessarily equate to nutrient return to the soil.  These nutrients may sit in the forest floor for a long time before they are decomposed.  Pinus litter in particular might take much longer to decompose than the native forest litter.  I still found many English errors throughout the manuscript.  With a change to the wording of nutrient return, I believe that this manuscript should have some minor revisions.

Line 49: instead of “fall of litterfall” consider just “litterfall”

Lines 91-93: What are the specific objectives of this study?  What are the hypotheses?

Lines 166-167: Multiplied is used twice in this sentence.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

 

Your contribution is of high scientific level, good structured, and with highly valuable output.

Some minimal additional explanations and broader interpretation would be useful.

 

Lines 18-21

Our results show that total litterfall production did not significantly influence the return of nutrients to the soil and litterfall nutrient efficiency, demonstrating that litterfall fractionation is essential to understand nutrient cycling and thus contributes to possible productivity gains in forest ecosystems.

 

Please explain the last part of this sentence in more details.

 

Lines 293-295

Our results show that the annual litterfall production of needles in the Pinus taeda plantation (6.68 Mg ha-1 yr-1 ), was significantly Forests 2021, 12, x FOR PEER REVIEW 12 of 16 higher than the leaves in the native forest (5.81 Mg ha-1 yr-1 ).

 

The difference between 6.68 and 5.81 is small (15%) concerning the biological objects.

In the case you discuss this difference can be caused by different tree species composition and/or difference of the management practice in the Pinus taeda plantation and in the native forest.

 

Lines 302-306

…the greater amount of leaves/needles fraction in the production of litterfall is crucial to accelerate the cycling of nutrients, since this is the fraction of the least recalcitrance in litterfall. This is directly related to a lower concentration of difficult-to-degrade materials, such as lignin, which contributes to the formation of labile soil organic matter and, consequently, increased soil fertility.

 

This statement is important. However, the long-term total nutrients reserve is not changed in the forest ecosystem. What do you think about the following model of forest nutrition: the Pinus taeda plantation is 6.68 Mg ha-1 yr-1, and we have some method to transform this litterfall into nutrients (Ln). Next year, the forest stand consumes this nutrients, and forms a corresponding biomass. The process repeats every year, and the total amount of consumed nutrients in the tree lifespan (N) will be Ln*N. If the difficult-to-degrade materials will be delayed for 5 years, then the amount of consumed nutrients in the tree lifespan (N) will be Ln*N/5. The shorter is a nutrient rotation, the higher is forest productivity. Of course, this is an abstract picture, but we ought to take in mind.

 

 

You rightly emphasized in Introduction section the need to account a reduced productivity and soil degradation in commercial forests in the next rotations. It would be great if you could develop this idea in your manuscript. The need to support the forest via new technologies is urgent. There are our proposals on this matter: https://doi.org/10.1016/j.envres.2020.110605 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Unfortunately the level of writing is not good enough for publication and i am not prepared to struggle through manuscripts with poor English. My only comment is that the English is not of a good enough standard for publication.

Author Response

Response to Reviewer 1 Comments

Unfortunately the level of writing is not good enough for publication and i am not prepared to struggle through manuscripts with poor English. My only comment is that the English is not of a good enough standard for publication.

Response: We thank the reviewer for the comment mentioned above. We agree with the comment that it would be beneficial to have the manuscript read by an English-speaking colleague. Following the reviewer's recommendations, we sent the manuscript back to an English translation company for corrections throughout the text.

We appreciate the reviewers' suggestions; we believe the manuscript has improved its quality based on the reviewers' comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

This study evaluated litterfall and nutrient return in Pinus taeda stand compared to the native forest in Southern Brazil. Only one stand of P. taeda and one of native forest were studied. 
In my opinion, it is a major flaw in the study design to draw conclusions regarding nutrient use efficiency and nutrient return based on only one P. taeda stand and one native stand. In addition, the authors did not adequately explain why they chose these particular stands for comparison. The description of the experimental design in the current version of the manuscript is far from sufficient to prove that the experiment was conducted according to all methodological standards. There is no information on whether the stands were contiguous to each other, whether soil type and fertility were the same for both stands, and it is not clear whether the description of soil and climate refers only to the native stand or to both comparable stands. I suspect that the data on the age of the native forest is insufficient, so it is better to describe the native forest and the P. taeda plantation by indicating their basal area. In general, it is expected that there will be differences when comparing stands with different species composition (deciduous and coniferous). It is also a well-known fact that monospecific cultures are more vulnerable to many threats and that litterfall production is directly related to a decrease in temperature and lower rainfall (conclusions). 
I provide some tips below on how to improve the description of the methodology. I hope they will be helpful for the authors to improve the paper.
It would be beneficial for the manuscript to add a map showing the locations of the two stands studied. It is imperative that the site conditions and stand characteristics were the same in the two stands compared (artificial and native). This is one of the most important rules in research methodology - Ceteris paribus - the only factor studied is different, the rest of the factors are the same in both stands. It would be good to extend the study to multiple stands (replications instead of pseudoreplications).
It would also be beneficial to have the manuscript read by an English-speaking colleague.

Author Response

Response to Reviewer 2 Comments

 

This study evaluated litterfall and nutrient return in Pinus taeda stand compared to the native forest in Southern Brazil. Only one stand of P. taeda and one of native forest were studied.

In my opinion, it is a major flaw in the study design to draw conclusions regarding nutrient use efficiency and nutrient return based on only one P. taeda stand and one native stand. In addition, the authors did not adequately explain why they chose these particular stands for comparison. The description of the experimental design in the current version of the manuscript is far from sufficient to prove that the experiment was conducted according to all methodological standards. There is no information on whether the stands were contiguous to each other, whether soil type and fertility were the same for both stands, and it is not clear whether the description of soil and climate refers only to the native stand or to both comparable stands. I suspect that the data on the age of the native forest is insufficient, so it is better to describe the native forest and the P. taeda plantation by indicating their basal area. In general, it is expected that there will be differences when comparing stands with different species composition (deciduous and coniferous). It is also a well-known fact that monospecific cultures are more vulnerable to many threats and that litterfall production is directly related to a decrease in temperature and lower rainfall (conclusions).

I provide some tips below on how to improve the description of the methodology. I hope they will be helpful for the authors to improve the paper.

It would be beneficial for the manuscript to add a map showing the locations of the two stands studied. It is imperative that the site conditions and stand characteristics were the same in the two stands compared (artificial and native). This is one of the most important rules in research methodology - Ceteris paribus - the only factor studied is different, the rest of the factors are the same in both stands. It would be good to extend the study to multiple stands (replications instead of pseudoreplications).

It would also be beneficial to have the manuscript read by an English-speaking colleague.

Response: We thank the reviewer for the comments and suggestions mentioned above. We agree with the general comments, given the size of the importance of forest types, such as natives and plantations, for the sector of the world economy, together with the great cultivation difficulties found in different environments, we believe that the results presented in this manuscript can help us to to visualize that the production and nutritional quality of litterfall depend on the composition of the species and the type of forest ecosystem.

However, we saw that there were small errors throughout the manuscript detected by reviewers. Based on this, we seek as many changes as possible for a better reformulation and, thus, we make it as clear as possible for the reader to understand the context of this study. Following the reviewer's recommendations, we sent the manuscript back to an English translation company for corrections throughout the text. We have added some information about the native forest, such as basal area and minimum age of management in the forest type, as per the reviewer's recommendations. Moreover, we agree with the reviewer that the addition of a map would contribute to better localization of the study for readers. In this way, we have added a map that is found in the current version of the manuscript.

We appreciate the reviewers' suggestions; we believe the manuscript has improved its quality based on the reviewers' comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript follows the litterfall types, weights, and nutrient contents of two forest types in Brazil.  I appreciate the large of amount of work that went into this manuscript.  This is an important manuscript to describe the effects of plantation forests on litter quality compared to native forests.  There are many English errors throughout the manuscript that need to be corrected.  Be careful describing litterfall nutrients as a return to the soil throughout the manuscript.  This manuscript studied the nutrient concentration and content of the litter and not the breakdown of litter into the soil.  I would be interested to see the nutrient concentrations of the litter of the two forest types, which could be included in the Appendix.  I believe that this manuscript should be accepted after minor revisions.

Lines 16-17: “which” is used three times in the same sentence.

Line 51: Do you mean planted or plantation instead of implanted?

Lines 95-98: Can you show a map of the two forests for readers outside of Brazil?  It would also be interesting to see a picture of the two forests.

Lines 106-107: I think you mean “Deep red clayey soils” because red is not a soil texture.

Lines 119-126: How old is the native forest? Or how large are the trees if the age is not known?

Line 168: “were analyzed” instead of “subjected to”

Line 191: “highest monthly production of twigs…”

Figure 2. Add in significant differences between the two forest types.

Table 2 should be moved to the Appendix.

Author Response

Response to Reviewer 3 Comments

 

This manuscript follows the litterfall types, weights, and nutrient contents of two forest types in Brazil.  I appreciate the large of amount of work that went into this manuscript.  This is an important manuscript to describe the effects of plantation forests on litter quality compared to native forests.  There are many English errors throughout the manuscript that need to be corrected.  Be careful describing litterfall nutrients as a return to the soil throughout the manuscript.  This manuscript studied the nutrient concentration and content of the litter and not the breakdown of litter into the soil.  I would be interested to see the nutrient concentrations of the litter of the two forest types, which could be included in the Appendix.  I believe that this manuscript should be accepted after minor revisions.

Response: We thank the reviewer for the comments and suggestions mentioned above. We agree with the general comments, given the size of the importance of forest types, such as natives and plantations, for the sector of the world economy, together with the great cultivation difficulties found in different environments, we believe that the results presented in this manuscript can help us to to visualize that the production and nutritional quality of litter depend on the composition of the species and the type of forest ecosystem.

However, we saw that there were small errors throughout the manuscript detected by reviewers. Based on this, we seek as many changes as possible for a better reformulation and, thus, we make it as clear as possible for the reader to understand the context of this study. Following the reviewer's recommendations, we sent the manuscript back to an English translation company for corrections throughout the text. We review the nutrient return throughout the text, seeking to reformulate the litter nutrient return, as suggested by the reviewer. In addition, we added the nutrient concentration in the supplemental material (Table S2), as recommended by the reviewer.

We appreciate the reviewers' suggestions; we believe the manuscript has improved its quality based on the reviewers' comments.

 

Lines 16-17: “which” is used three times in the same sentence.

Response: Thanks for the reviewer checking this out. We modify it on the spot recommending it.

 

Line 51: Do you mean planted or plantation instead of implanted?

Response: We appreciate the reviewer's comment. We changed it to "planted", as recommended by the reviewer.

 

Lines 95-98: Can you show a map of the two forests for readers outside of Brazil?  It would also be interesting to see a picture of the two forests.

Response: We agree with the reviewer that the addition of a map would contribute to better localization of the study for readers. In this way, we have added a map that is found in the current version of the manuscript.

 

Lines 106-107: I think you mean “Deep red clayey soils” because red is not a soil texture.

Response: Thanks for the reviewer checking this out. We agree that this sentence needed rewording. Based on this, we made the modifications as suggested by the reviewer.

 

Lines 119-126: How old is the native forest? Or how large are the trees if the age is not known?

Response: Thanks for the reviewer checking this out. We have added some information about the native forest, such as basal area and minimum age of management in the forest type, as per the reviewer's recommendations.

 

Line 168: “were analyzed” instead of “subjected to”

Response: We appreciate the reviewer's comment. We made the suggested modifications.

 

Line 191: “highest monthly production of twigs…”

Response: We are grateful that the reviewer has verified this. We modified it according to the reviewer's recommendation.

 

Figure 2. Add in significant differences between the two forest types.

Response: We appreciate the reviewer's comment. We added the statistical difference between the two forest types, as suggested by the reviewer.

 

Table 2 should be moved to the Appendix.

Response: Thanks for the reviewer's comment. We moved the table to supplementary material as per the reviewer's recommendations.

Author Response File: Author Response.pdf

Reviewer 4 Report

Authors present data describing “Litterfall and nutrient return in Pinus taeda stand and native forest’ in Southern Brazil. Overall I believe that the paper has scientific merit, and the questions about how forest types can influence on litterfall production and nutrient return in a Subtropical Seasonal Forests. However, it is difficult to justify the results because of the lack of basic stand and soil information data, such as stand basal area, soil physical and chemical properties which are very important to understand the study results. In addition, nutrient concentration in litterfall components should be provided in the manuscript.

Abstract

You should be careful with the conclusion. The sentence of line 17-21 should be rewritten with your study results related to the different type of forests, not as a general statement.  

Line 20: use one term in the manuscript (stand or plantation)

Line 76: delete Thus?

Line 96-97. Provide the map of the study sites.

Line 121: 1.500 -> 1,500

Line 139: how about big branches (> 2 mm diameter). Is there no big branches litterfall?

Line 159: Show an equation how nutrient returns calculate.

Line 168-170: You could add the way for checking normality of the data.

Line 190, 196, 212, 321, 347, 400: please use other terms such as forest types instead of forest ecosystem

Line 206: n=4 ?? . The description of the study design is a bit confusing. You have three plots with four litter litter traps in each plot. did I understand correctly?

Line 225: Please check the values of N and P (11,57kg N ha-1, 22.11kg P ha-1) with Figure 4.

Line 238-240, 332-336. Annual return: kg ha-1 yr-1. Add yr-1

Line 338. To justify this result, you need to show soil information in the manuscript.

Line 399. You should show hypothesis of this study in Introduction section.

Line 405-408. The sentences should be based on the result of statistical analysis between litterfall production and climatic factor.  

Figure 3, Figure 5. : add the title in X-axis

Figure 3. Add yr-1 in Y-axis (Mg ha-1 yr-1)

Table 2. Please consider to move to Appendix

Figure 6. check typographical errors within the figure, e.g. Totall literfall, literfall.

Check references. Many repetitions of year (e.g.2, 12, 19, 38 etc.)

 

Author Response

Response to Reviewer 4 Comments

 

Authors present data describing “Litterfall and nutrient return in Pinus taeda stand and native forest’ in Southern Brazil. Overall I believe that the paper has scientific merit, and the questions about how forest types can influence on litterfall production and nutrient return in a Subtropical Seasonal Forests. However, it is difficult to justify the results because of the lack of basic stand and soil information data, such as stand basal area, soil physical and chemical properties which are very important to understand the study results. In addition, nutrient concentration in litterfall components should be provided in the manuscript.

Response: We are thankful for the reviewer for the comments and suggestions mentioned above. We agree with the general comments, given the size of the importance of forest types, such native and plantation, for the world economy sector, coupled with the great cultivation difficulties found in the different environments, we believe that the results presented in this manuscript can help us to visualize that production and nutritional quality of the litterfall depends on the composition of the species and the type of forest ecosystem. The results found in the manuscript may help farmers and technicians to the understanding that litterfall acts to maintain soil fertility in forest ecosystems, both native and implanted, as it is the main source of soil organic material, enabling greater availability of adequate nutrients, which will contribute to the satisfactory growth of forest types.

However, we saw that there were minor errors throughout the manuscript detected by the reviewers. From this, we seek as much as possible changes for its better reformulation and, thus, make it as clear as possible for readers to understand the context of this study.

 

Abstract

 

You should be careful with the conclusion. The sentence of line 17-21 should be rewritten with your study results related to the different type of forests, not as a general statement. 

Response: We appreciate the reviewer's comments. We agree that the summary conclusion should be rewritten with the results of your study related to different forest types. Thus, we reformulated according to the reviewer's suggestions.

 

Line 20: use one term in the manuscript (stand or plantation)

Response: Thanks for the reviewer verifying this. We have adapted this term throughout the manuscript.

 

Line 76: delete Thus?

Response: We appreciate the reviewer for commenting on this. We delete this word from the sentence, as recommended.

 

Line 96-97. Provide the map of the study sites.

Response: We agree with the reviewer that the addition of a map would contribute to better localization of the study for readers. In this way, we have added a map that is found in the current version of the manuscript.

 

Line 121: 1.500 -> 1,500

Response: We appreciate the reviewer's comment. We made the suggested modifications.

 

Line 139: how about big branches (> 2 mm diameter). Is there no big branches litterfall?

Response: Thanks for the reviewer checking this out. We saw that this classification was wrong. We reformulated according to the reviewer's suggestions.

 

Line 159: Show an equation how nutrient returns calculate.

Response: We appreciate the reviewer mentioning this. We added the nutrient return calculation methodology and its respective reference.

 

Line 168-170: You could add the way for checking normality of the data.

Response: Thanks for the reviewer checking this out. We have added this procedure along with the statistical analysis subsection in the material and methods section, as suggested by the reviewer.

 

Line 190, 196, 212, 321, 347, 400: please use other terms such as forest types instead of forest ecosystem

Response: Thanks for the reviewer checking this out. We modify it on the spot recommending it and also throughout the manuscript.

 

Line 206: n=4 ?? . The description of the study design is a bit confusing. You have three plots with four litter litter traps in each plot. did I understand correctly?

Response: We are grateful that the reviewer has verified this. The reviewer's understanding is correct. In the present study, we had four replicates (n=4), within each of the three plots. One plot per block, totalling 12 litter traps per forest type. We seek to improve clarity with the manuscript. We hope this has been made clearer to the reviewer as well as to readers.

 

Line 225: Please check the values of N and P (11.57 kg N ha^-1, 22.11 kg P ha^-1) with Figure 4.

Response: We appreciate the reviewer's comment. We made the suggested modifications.

 

Line 238-240, 332-336. Annual return: kg ha^-1 yr^-1. Add yr^-1

Response: Thanks for the reviewer checking this out. We modify it on the spot recommending it and also throughout the manuscript.

 

Line 338. To justify this result, you need to show soil information in the manuscript.

Response: Thanks for the reviewer mentioning this. We agree that results and information from the soil would help to help with explanations in the manuscript. However, on occasion we do not carry out soil analysis. Based on this, we tried to reformulate this paragraph, as suggested by the reviewer.

 

Line 399. You should show hypothesis of this study in Introduction section.

Response: We appreciate the reviewer's comment. However, we saw that the hypothesis of this study mentioned is in the introduction section. We decided to reformulate and seek to improve throughout the manuscript.

 

Line 405-408. The sentences should be based on the result of statistical analysis between litterfall production and climatic factor. 

Response: We appreciate the reviewer's comments. We agreed with the reviewer and decided to reformulate following the changes as suggested.

 

Figure 3, Figure 5. : add the title in X-axis

Response: We appreciate the reviewer's comment. We made the suggested modifications.

 

Figure 3. Add yr^-1 in Y-axis (Mg ha^-1 yr^-1)

Response: We are grateful that the reviewer has verified this. We modified it according to the reviewer's recommendation.

 

Table 2. Please consider to move to Appendix

Response: Thanks for the reviewer's comment. We moved the table to supplementary material as per the reviewer's recommendations.

 

Figure 6. check typographical errors within the figure, e.g. Totall literfall, literfall.

Response: We are grateful that the reviewer has verified this. We modified it according to the reviewer's recommendation.

 

Check references. Many repetitions of year (e.g.2, 12, 19, 38 etc.)

Response: Thanks for the reviewer's comment. We modified as recommended in these references, as well as others that had some details to be formatted.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I rejected the original manuscript because of significant flaws in the study design. The study only considers one forest stand from each treatment (native vs. plantation), so this study uses pseudoreplications instead of replications. Additional test sites are needed to improve the current study. The authors were unable to change this in the improved version of the manuscript. 
Although the manuscript has been improved overall, the authors' response to my comments is too vague. In fact, only one comment was addressed by adding the map of the study area, which indeed is very helpful but does not cover my other comments. Therefore, I have to stick to my earlier opinion.

Reviewer 4 Report

Comments,

Although the manuscript has been revised, the most important data are still missing (stand, soil, monthly nutrient concentration of litterfall components etc.).  In addition, author should justify the pseudoreplication design in this study.