Round 1

Reviewer 1 Report

Tree diversity at different spatial scales

1.      Write this section in more detail for reader interest and understanding of the data. Also, explain the figure-2 for reader interest and understanding.

Ecological drivers of tree diversity

2.      The measured ecological variables explaining the variation in tree species composition at the three spatial scales were 24.3%, 26.5% and 38.5%, respectively (Figure 3). Climatic factors explained the most independent fraction of tree diversity at the three grid scales (9.6%, 11.1% and 12.5%), but a small independent fraction was explained by topography (2.9%, 2.7% and 4.3%) and forest structure (4.2%, 3.9% and 5.0%). The combined explanations of the three components were 2.6%, 3.2% and 8.1%, respectively, with spatial scale. What is the possible reason of it? Please support your result with the help of available literature.

3.      The DBH cv influenced most on tree richness, and followed by AP mean and AMT mean, with relative contributions of 26.6%, 24.5% and 14.0% at the 10 km × 10 km spatial scale. What is the possible reason of it? Please support your result with the help of available literature.

4.      AP mean was strongest impact, followed by AMT mean and DBH cv, with relative contributions of 21.6%, 20.0% and 18.3% at the 30 km × 30 km spatial scale. AP mean contributed most, followed by ASD mean and EL cv, with relative contributions of 23.6%, 18.7% and 13.4% at the 90 km × 90 km spatial scale. What is the possible reason of it? Please support your result with the help of available literature.

5.      The DBH cv had the greatest impacted the Shannon index, followed by the AMT mean and AMT cv, with relative contributions of 31.6%, 23.7% and 9.3% at the 10 km × 10 km spatial scale. What is the possible reason of it? Please support your result with the help of available literature.

6.      AMT mean had the strongest influence, followed by DBH cv and AMT cv, with relative contributions of 30.2%, 20.3% and 14.3% at the 30 km × 30 km spatial scale. AMT cv contributed the most, followed by AMT mean and EL cv, with relative contributions of 28.7%, 28.1% and 16.4% at the 90 km × 90 km spatial scale. What is the possible reason of it? Please support your result with the help of available literature.

7.      In Figure 4, the three index of tree diversity responding to AMT mean and AMT cv had similar variation trends on different scales, but the extent of each was diverse. What is the possible reason of it? Please support your result with the help of available literature.

8.      The Simpson index changed with the TH mean in a hump-shaped manner at the 10 km × 10 km scale but decreased with the TH mean in an ascending ladder type. What is the possible reason of it? Please support your result with the help of available literature.

Conclusion

9.      Please rewrite conclusion which includes highlights of your results.

10.  What you recommend for future?

 

11.  What are the benefits of this study?

Minor check is required for the language.

 

Author Response

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

In the results and discussion sections, the presentation and discussion were not thorough enough, making the article seem too simple.

No

Author Response

Dear reviewer, thank you for your opinions. We will try to improve in future research.

Reviewer 3 Report

The manuscript is devoted to the study of environmental factors and forest structure that affect tree species diversity. This issue is important and relevant in the light of current environmental problems and the ongoing loss of biodiversity due to climate change and human activities. A number of shortcomings must be corrected before publication.

 

1)     In the Results section, the authors claim that in a number of cases they found humpbacked dependencies of diversity indicators on environmental factors and indicators of forest structure. As proof, Fig. 4. However, it shows that the discussed humps are almost invisible and we are talking more about positive or negative dependencies. If the authors actually found non-linear humpback relationships, it should be explicitly explained that they are statistically significant.

2)     In the Discussion section, the authors state that their results support the intermediate disturbance hypothesis (IDH). This is an erroneous statement. Results, obtained by authors are not related to the IDH, since IDH talks about medium intensity of disturbances. Authors do not consider disturbance as a factor influencing diversity. Obtained results can be explained by a number of other hypotheses about hump- back dependence of diversity on environmental factors.

 

Minor comments. Since there are no line numbers in the manuscript, please see the attached PDF file for the exact linking of the comments.

 

Page: 1

Paragraph 2. Further in this paragraph, there is nothing about depending on the scale. A bit illogical

 

Page 2

Paragraph 1. A contradictory statement that needs explanation. But there is no such explanation in the given references. It might be better to remove it.

Paragraph 1. The intermediate disturbance hypothesis suggests that the number of species is maximum at an average disturbance intensity. And Grim, in the work you mentioned, puts forward another hypothesis that the number of species is maximum at an average level of stress. It is desirable to cite the literature more precisely

Paragraph 2. The regional level was not explicitly discussed above.

Paragraph 2. Rephrase, please. Now it turns out a tautology: the number of species affects the species diversity

Paragraph 3. This phrase is incomprehensible. Rephrase please

Paragraph 4. It's in the Methods section. Repetition should be removed

 

Page 3

Paragraph 1. This is more like a repetition of the obtained results, rather than hypotheses. If these are your hypotheses that you formulated before the study and tested them on the data obtained, then it is necessary to explain the logical premises on the basis of which you formulated these  hypotheses

 

Page 4

Paragraph 3. SMI is absent in the Table 1

Paragraph 3. What is TWI?

 

Page 5

Fig. 2 Letters cannot indicate differences between scales, they can only indicate scales. But do we need this additional indexes if the scale is signed on the Х-axis?

 

Page 6

Paragraph 2. Perhaps it's more accurate to say that DBHcv statistically "explains" richness, not more.

DBHcv and richness are interrelated features of structure of forest communities. What influences what - this still needs to be dealt with

Paragraphs 2-4. It is not necessary to repeat in these three paragraphs the data from Table 1

 

Page 7

Table 1. It would be useful to divide the indicators in the table into three groups discussed in the text: climatic, topographic and forest structure

What is TWI?

SMI is absent in the table

The last paragraph. There is no bump in fig. 4

The last paragraph.  The hump is almost invisible. Rather, a weak negative dependency. The same can be said about other "humps"

 

Page 8

Paragraph 2. This article does not contain data about species composition. Species composition, species richness and species diversity are different terms. You are discussing only the last two

Paragraph 2. Fig. 4 does not show it. This can be seen from fig. 2

 

Page 9

Paragraph 2. Does that mean "consistent"? It should be clarified here that results of Chu may be not contradict your results, since Chu considers intra-annual variability, while you consider inter-annual variability. But reasoning of Chu is completely opposite to yours: Species adapted to more abiotically variable habitats can tolerate wider range of abiotic conditions and therefore have wider niches/ looser “packing”, which results in fewer species. This is what should be explained. As it stands, your argument about the results of Chu is not good

Paragraph 2. This is not related to the IDH, since IDH talks about medium intensity of disturbances. This can be explained by a number of other hypotheses about hump- back dependence of diversity on environmental factors, which are worth mentioning here.

 

Page 10

Paragraph 1. This reasoning seems strange, since increased competition just leads to the dominance of the most powerful competitors.

Paragraph 1. See comment about IDH on page 9

Paragraph 2. See comment about composition on page 8

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments and Suggestions

Comments and Suggestions for Authors

The manuscript is devoted to the study of environmental factors and forest structure that affect tree species diversity. This issue is important and relevant in the light of current environmental problems and the ongoing loss of biodiversity due to climate change and human activities. A number of shortcomings must be corrected before publication.

 

Point 1: In the Results section, the authors claim that in a number of cases they found humpbacked dependencies of diversity indicators on environmental factors and indicators of forest structure. As proof, Fig. 4. However, it shows that the discussed humps are almost invisible and we are talking more about positive or negative dependencies. If the authors actually found non-linear hump-back relationships, it should be explicitly explained that they are statistically significant.

Response 1: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L256-259) Tree richness increased with the AMT _mean and then decreased slightly at the 10 km × 10 km, 30 km × 30 km and 90 km × 90 km scale. (L263-265) The Simpson index decreased with the TH _mean in an ascending ladder type.

Point 2: In the Discussion section, the authors state that their results support the intermediate disturbance hypothesis (IDH). This is an erroneous statement. Results, obtained by authors are not related to the IDH, since IDH talks about medium intensity of disturbances. Authors do not consider disturbance as a factor influencing diversity. Obtained results can be explained by a number of other hypotheses about hump-back dependence of diversity on environmental factors.

Response 2: Dear reviewer, thank you for your detailed opinions. We have modified the intermediate disturbance hypothesis (IDH) to the intermediate stress hypothesis (ISH) (L64 and L306).

Point 3: Minor comments. Since there are no line numbers in the manuscript, please see the attached PDF file for the exact linking of the comments.

Response 3: Dear reviewer, thank you for your opinions. We have added the line numbers and responded with them.

Page: 1

Point 4: Paragraph 2. Further in this paragraph, there is nothing about depending on the scale. A bit illogical.

Response 4: Dear reviewer, thank you for your detailed opinions. Here, we want to illustrate the scale dependence of different environmental factors, such as the climate and topography (L50-53), and the scale dependence of species, such as the species range increased with niche width (L56-58). We have modified it to: (L50-53) Climate, as one of the most important abiotic factors, has a strong impact on biodiversity across large spatiotemporal scales than small scales [3,6,16], and topographic factors, especially altitude, are thought to be more associated with diversity in regional scales than local scale [17].

Page 2

Point 5: Paragraph1. A contradictory statement that needs explanation. But there is no such explanation in the given references. It might be better to remove it.

Response 5: Dear reviewer, thank you for your detailed opinions. We have removed it (L62-63).

Point 6: Paragraph1. The intermediate disturbance hypothesis suggests that the number of species is maximum at an average disturbance intensity. And Grim, in the work you mentioned, puts forward another hypothesis that the number of species is maximum at an average level of stress. It is desirable to cite the literature more precisely.

Response 6: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L63-65) The intermediate stress hypothesis (ISH) demonstrates that species diversity would likely peak at medium level of environmental gradients [29].

Point 7: Paragraph 2. The regional level was not explicitly discussed above.

Response 7: Dear reviewer, thank you for your opinions. The scale dependence of environmental factors and species we discussed above are all at regional level (Response 4).

Point 8: Paragraph 2. Rephrase, please. Now it turns out a tautology: the number of species affects the species diversity.

Response 8: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L69-72) In contrast to the regional scale, the horizontal and vertical structure of forest, including the number and size of coexisting tree individuals in community, closely influences species diversity at the local scale by changing the energy distribution in the community [31].

Point 9: Paragraph 3. This phrase is incomprehensible. Rephrase please.

Response 9: Dear reviewer, thank you for your detailed opinions. Here, we want to explain the ecological implication of the four diversity which representing different aspects of biodiversity. We have modified it to: (L86-91) Community represents the different species assembling in a space; species richness is the actual number of species in the community; species evenness (weighting individual abundance of each specie in the community) and species dominance (representing the relative percentage of species in the community) can reflect the development of the community.

Point 10: Paragraph 4. It's in the Methods section. Repetition should be removed.

Response 10: Dear reviewer, thank you for your opinions. We have removed it (L98-101).

Page 3

Point 11: Paragraph 1. This is more like a repetition of the obtained results, rather than hypotheses. If these are your hypotheses that you formulated before the study and tested them on the data obtained, then it is necessary to explain the logical premises on the basis of which you formulated these hypotheses.

Response 11: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L106-108) (I) the effect of ecological factors driving tree diversity increase with spatial scale; (II) various factors affecting tree diversity on different spatial scales.

Page 4

Point 12: Paragraph 3. SMI is absent in the Table 1. & What is TWI?

Response 12: Dear reviewer, thank you for your detailed opinions. We have modified TWI to SMI, which is soil moisture index.

 

Page 5

Point 13: Fig. 2 Letters cannot indicate differences between scales, they can only indicate scales. But do we need this additional indexes if the scale is signed on the Х-axis?

Response 13: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L206-207) The letters a, b and c indicate significant differences of the diversity among different spatial scales.

Page 6

Point 14: Paragraph 2. Perhaps it's more accurate to say that DBHcv statistically "explains" richness, not more.

Response 14: Dear reviewer, thank you for your detailed opinions. Yes, it is. However, we need to compare it with other factors on different scales. We have modified it to: (L231) The DBH _cv statistically influenced most on tree richness, and followed by AP _mean and AMT _mean…; (L237) The DBH _cv had the greatest statistical impact on the Shannon index, followed by the AMT _mean and AMT _cv…; (L243) For the Simpson index (Table 1), DBH _cv had the greatest statistical influence, followed by AMT _mean and TH _mean…

Point 15: DBHcv and richness are interrelated features of structure of forest communities. What influences what - this still needs to be dealt with.

Response 15: Dear reviewer, thank you for your detailed opinions. Yes, they are. Here, we mainly take DBH as a biotic factor and study its influence on richness. We will pay attention to this problem in future studies.

Point 16: Paragraphs 2-4. It is not necessary to repeat in these three paragraphs the data from Table 1.

Response 16: Dear reviewer, thank you for your detailed opinions. We have removed them (L231-248).

Page 7

Point 17: Table 1. It would be useful to divide the indicators in the table into three groups discussed in the text: climatic, topographic and forest structure.

Response 17: Dear reviewer, thank you for your detailed opinions. We have modified it in table 1 (L205-251).

Point 18: What is TWI? & SMI is absent in the table.

Response 18: Dear reviewer, thank you for your detailed opinions. We have modified TWI to SMI in table 1.

Point 19: The last paragraph. There is no bump in fig. 4

Response 19: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L256-259) Tree richness increased with the AMT _mean and then decreased slightly at the 10 km × 10 km, 30 km × 30 km and 90 km × 90 km scale.

Point 20: The last paragraph.  The hump is almost invisible. Rather, a weak negative dependency. The same can be said about other "humps".

Response 20: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L263-265) The Simpson index decreased with the TH _mean in an ascending ladder type.

Page 8

Point 21: Paragraph 2. This article does not contain data about species composition. Species composition, species richness and species diversity are different terms. You are discussing only the last two.

Response 21: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L278) The results showed that the strong dependence of tree species diversity…(Figure 2).

Point 22: Paragraph 2. Fig. 4 does not show it. This can be seen from fig. 2

Response 22: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L279) The results showed that the strong dependence of tree species diversity…(Figure 2).

Page 9

Point 23: Paragraph 2. Does that mean "consistent"? It should be clarified here that results of Chu may be not contradict your results, since Chu considers intra-annual variability, while you consider inter-annual variability. But reasoning of Chu is completely opposite to yours: Species adapted to more abiotically variable habitats can tolerate wider range of abiotic conditions and therefore have wider niches/ looser “packing”, which results in fewer species. This is what should be explained. As it stands, your argument about the results of Chu is not good.

Response 23: Dear reviewer, thank you for your detailed opinions. Yes, it is. We have modified it to: (L296) …which is consistent with our results.

Point 24: Paragraph 2. This is not related to the IDH, since IDH talks about medium intensity of disturbances. This can be explained by a number of other hypotheses about hump-back dependence of diversity on environmental factors, which are worth mentioning here.

Response 24: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L304-306) We found that tree diversity responded to temperature in a slight hump-type manner at the medium scale, which consists with the intermediate stress hypothesis (ISH).

Page 10

Point 25: Paragraph 1. This reasoning seems strange, since increased competition just leads to the dominance of the most powerful competition on page 8.

Response 25: Dear reviewer, thank you for your detailed opinions. We have modified it to: (L341-346) …but there was a negative relationship between tree height and the Simpson index. The results showed that an excessive tree height of the lager tree can reduce dominance of community by increasing disproportional species competition with small trees as the shading effect, although a diversified tree height could increase vertical space and promote diversity.

Author Response File: Author Response.pdf