Recovery of Logged Tropical Montane Rainforests as Potential Habitats for Hainan Gibbon

Round 1

Reviewer 1 Report

An interesting and written article. The research is scientifically sound, and I think it will make an important contribution to the conservation of the Hainan gibbon, while also fitting into the wider literature of secondary forest growth. I have some minor comments regarding the abstract, figures, and equations, as well as some typos that I have identified in the text. I attach these in the document below. Please note, my comments on figure 1 and 2 should replicate for all your figures. They need cleaning, larger labels, a legend, and better use of your space. 

Comments for author File: Comments.pdf

Author Response

Comment from Reviewer 1:

An interesting and written article. The research is scientifically sound, and I think it will make an important contribution to the conservation of the Hainan gibbon, while also fitting into the wider literature of secondary forest growth. I have some minor comments regarding the abstract, figures, and equations, as well as some typos that I have identified in the text. I attach these in the document below. Please note, my comments on figure 1 and 2 should replicate for all your figures. They need cleaning, larger labels, a legend, and better use of your space.

Response: Thanks for your affirmation and kind comments on this manuscript. All comments were responded one by one. We hope this revision can reach the requirement for publishing.

 

Point 1: I would have one aim statement in the abstract as it’s not 100% clear what you are trying to achieve

Response 1: I’ m sorry that we didn’t make our aim clearly enough. We added it in the abstract as “To explore the recovery of secondary tropical rainforests after different disturbances, and whether they have the potential to serve as the future habitats for Hainan gibbon, we calculated 4 dynamic indexes (including recruitment rate, mortality/loss rate, relative growth rate and turnover rate) of abundance and basal area for the total community and for food plants of Hainan gibbon based on data from two censuses of secondary forests recovered nearly 45 years after different disturbances (clear-cutting and selective-logging) and old-growth forest of tropical montane rainforest”.

 

Point 2: Line 50 “National Park of Hainan Tropical Rainforest” to “a National Park of Hainan Tropical Rainforest”.

Response 2: Sine the National Park of Hainan Tropical Rainforest was already established in 2019. We changed the sentence to “Therefore, the protection of Hainan gibbon will play a crucial guiding role in improving the conservation efficiency of the National Park of Hainan Tropical Rainforest.

 

Point 3: Line 51 “field researches”.

Response 3: We changed the “field researches” to “field research” in the manuscript.

 

Point 4: Line 70 delete “Besides”.

Response 4: It has been deleted in the manuscript.

 

Point 5: Line 83 “is most likely” to “are most likely”.

Response 5: It has been changed in the manuscript.

 

Point 6: Line 109 “is long-term debate” to “is a long-term debate”.

Response 6: It has been changed in the manuscript.

 

Point 7: There are two spaces in Line 125.

Response 7: We deleted one space in the manuscript.

 

Point 8: Line 134 delete “here”.

Response 8: It has been deleted in the manuscript.

 

Point 9: Line 140- Line 145: This is data collection, not study site.

Response 9: We replaced these sentences to “Data collection” part. Please see detailed information in the “Materials and Methods” in the manuscript.

 

Point 10: List these separately, they are not clear at the moment. At the end of each equation, you should explain the algebra, not after listing all three

Response 10: We listed and explained these equations separately, please see the part “Calculation formula” in the manuscript for detailed information.

 

Point 11: In the base package or in specialised packages? If specialised packages, cite accordingly.

Response 11: SMA was performed by the smatr package, others were run by base packages. We added the relevant information in the “Statistical analysis” in the manuscript.

 

Point 11: Legend needed to show differences between the colors if the caption is on a different. Labels could be a bit larger.

Response: We have redrawn all the figures in the manuscript and the supplementary information. In each picture, we added the legends and amplified the labels.

 

Point 12: An interesting paragraph. Perhaps just reiterate the nuances of initial v long-term. Surely this fits in with the wider landscape configuration as well? Clear-cutting is effective at regenerating similar conditions, but if the whole area is felled then there is no support nearby. I would just state the nuances and suggest more research is needed, as it could be seen as a green light to completely clear-fell areas, which would contradict the very good conservation message in this article.

Response 12: In this study, we did find that clear-cutting forests might be better recovered than selectively-logged forests. We think this result may be due to the following reasons. Firstly, the intensity of selective logging on Hainan island is much higher than in other tropical regions, with at least 60% of the timber volume harvested during the logging process. Secondly, seeds from old-growth forest spread easily into clear-cut areas, and the high available light after clear-cutting creates better conditions for the recruitment of long-lived pioneer species. Moreover, the practice of controlled burning after clear-cutting further provides abundant nutrients for these rapid resource-use pioneer species. Thirdly, selectively-logged forests have better initial conditions (such as the number of mother trees, regional species pool, etc.) than clear-cutting forests. This suggested that competition caused by the density-dependent factors may play a more important role in regulating community dynamics in selectively-logged forests, which was consistent with the higher mortality rates in selectively-logged forests than in clear-cutting forests. Lasty, due to the less disturbance intensity of selectively-logged forests, these secondary forests had gradually stepped into the later successional stage after 45-year-recovery. At this time, the forests had large abundance, high community density and the intense inter-/intra-specific competition, which could cause low relative growth rates. Meanwhile, clear-cutting forests may be in the initial stage of recovery with a small abundance and a fast growth rate. However, the instantaneous results of this study do not represent permanent conclusions, and we think longer-term effect of logging on tree communities and particularly logging intensity on demographic rate is still needed. 

Reviewer 2 Report

Forests of Hainan island are evaluated as the potential habitat for Hainan gibbon. 3 handling types (clear-cutting, selective lodging, old-growth) are evaluated by 4 parameters and differences are shown for food and non-food plants, as well as small/medium and large plants.

The manuscript provides very interesting information, it is written in a clear and understandable way, its English is also good.

Some remarks:

In order to better understand habitat suitability, some information on predators and/or parasites would be great to see. I am not sure if there is any large-bodies predators on the island but changes of the vegetation might onfuence parasite distribution, for example. Any results here?

It is often unclear if "small" means a small species or also the small individuals of large species. Please clarify.

We learn that the key limitation is the lack of large food plants. Is it really the size or some other life history parameer that is linked, maybe accidentally to size?

It is very interesting to see that the difference between the clear-cut and selectively logged forests is not big. In some cases, the clear-cut i even closer to the old-growth forest than to the selectively logged forest. This is surpsrising, at least my expectation was that the OG and the SL are closer to each other in many parameters. A little bit more discussion of the relevant literature would be needed in 4.3, especially on the intensity of SL and whether this pattern has been found elsewhere.

I think that some more outlook would be useful for the factors influencing regeneration (e.g. the fate of seeds), let me suggest two case studies as examples:

For the amount and success of seeds, this paper might be of consideration:
https://www.jstor.org/stable/4091990?casa_token=DLoNlf9WQjEAAAAA%3A8v38IH0WAf-NB_rnh__xW6NA9Qcwq4wuyZsLPJ6R9Xiqoc4j3T-1nHKtUaBVxw8sCV_79j2BQetnu5Dmh_BJLBfa6O2Ucokl4Zc6fQ7VnnlFlEBaNA&seq=1#metadata_info_tab_contents

For various factors influencing regeneration, see this great study:
https://link.springer.com/article/10.1007/s42974-020-00021-8

Avoiding edge effect is a good idea, it is acknowledged. Also, repeating the census 5 years later is a good approach.

Choosing 3 * 2 locations is not too many, statistically speaking. Since vegetation sampling is not very complicated (compared to animal traps, for example), more locations could have been better, I think.

Minor:

line 125: there is a double-space here
line 128: do not start the sentence with "And"
line 364, 375: "On the one hand" and "On the other hand" are very far from each other, it is hard to follow the logic. I suggest to start a new paragraph in both cases, to help the reader.

Author Response

Comment from Reviewer 2:

Forests of Hainan island are evaluated as the potential habitat for Hainan gibbon. 3 handling types (clear-cutting, selective lodging, old-growth) are evaluated by 4 parameters and differences are shown for food and non-food plants, as well as small/medium and large plants.

The manuscript provides very interesting information, it is written in a clear and understandable way, its English is also good.

Response: Thanks for your affirmation and kind comments on this manuscript. All comments were responded one by one. We hope this revision can reach the requirement for publishing.

 

Point 1: In order to better understand habitat suitability, some information on predators and/or parasites would be great to see. I am not sure if there are any large-bodies predators on the island but changes of the vegetation might influence parasite distribution, for example. Any results here?

Response 1：There are few large predators and few parasites on Hainan island that can affect the survival and growth of Hainan gibbon. We searched the Web of Science and Google with strings “gibbon” and “predator” or “parasite” or “natural enem%”, and found few relevant results. References indicated that as strictly arboreal primates, gibbons may be better protected from predation than other groups of primates with comparable body and group sizes due to their highly specialized rapid locomotion and preference for the high canopy. And Predation on gibbons is rarely observed in the wild (Uhde and Sommer, 2002; .

Uhde NL, Sommer V (2002) Antipredatory behavior in gibbons (Hylobates lar, Khao Yai/Thailand). In: Miller LE (ed) Eat or be eaten. Cambridge University Press, Cambridge, pp 268–292.

Esther Clarke & Ulrich H. Reichard & Klaus Zuberbühler. The anti-predator behaviour of wild white-handed gibbons (Hylobates lar). Behav Ecol Sociobiol (2012) 66:85–96

Point 2: It is often unclear if "small" means a small species or also the small individuals of large species. Please clarify.

Response 2：In this study, "small" means small individuals of species. We stated it in the part “Statistical analysis”. In order to compare the demographic dynamics of woody plants with different DBH classes in the three forest types, all woody plants with DBH ≥ 1 cm in the plots were divided into three size groups: small trees (1 ≤ DBH < 10 cm), medium trees (10 ≤ DBH < 30 cm) and large trees (DBH ≥ 30 cm).

 

Point 3: We learn that the key limitation is the lack of large food plants. Is it really the size or some other life history parameter that is linked, maybe accidentally to size?

Response 3: The availability of food resources is a major determinant of habitat quality for animals. Understanding the community dynamics of food plants for gibbons is important to evaluate the population growth potential of Hainan gibbon and to put forward the conservation measures of this critically endangered primate. In this study, we focused on recovery of secondary montane rainforests as potential habitats for Hainan gibbon, highlighting the composition and dynamic of food plants. There were no significant differences in dynamic indexes and growth rate between recovered clear-cutting forests, selective logging forests and the old-growth forests, while abundance, basal area and species of large food plants (DBH ≥ 30cm) in the two disturbed forests were lower than in old-growth forests. Therefore, we think the lack of large food plants is the key limiting factor for the development of the secondary mountain rainforest as habitats for Hainan gibbon at present. Thick branches from big trees can provide good places for activities of gibbon according to their living habits. At the same time, large food plants can also provide high-quality fruits for gibbon. We agree with you that there may be some other life history parameters that is linked (such as differences in fruit quality among tree sizes), which we are going to explore in our future research.

 

Point 4: It is very interesting to see that the difference between the clear-cut and selectively logged forests is not big. In some cases, the clear-cut i even closer to the old-growth forest than to the selectively logged forest. This is surprising, at least my expectation was that the OG and the SL are closer to each other in many parameters. A little bit more discussion of the relevant literature would be needed in 4.3, especially on the intensity of SL and whether this pattern has been found elsewhere.

Response 4: In this study, we did find that clear-cutting forests might be better recovered than selectively-logged forests. We think this result may be due to the following reasons. Firstly, the intensity of selective logging on Hainan island is much higher than in other tropical regions, with at least 60% of the timber volume harvested during the logging process. Secondly, seeds from old-growth forest spread easily into clear-cut areas, and the high available light after clear-cutting creates better conditions for the recruitment of long-lived pioneer species. Moreover, the practice of controlled burning after clear-cutting further provides abundant nutrients for these rapid resource-use pioneer species. Thirdly, selectively-logged forests have better initial conditions (such as the number of mother trees, regional species pool, etc.) than clear-cutting forests. This suggested that competition caused by the density-dependent factors may play a more important role in regulating community dynamics in selectively-logged forests, which was consistent with the higher mortality rates in selectively-logged forests than in clear-cutting forests. Lasty, due to the less disturbance intensity of selectively-logged forests, these secondary forests had gradually stepped into the later successional stage after 45-year-recovery. At this time, the forests had large abundance, high community density and the intense inter-/intra-specific competition, which could cause low relative growth rates. Meanwhile, clear-cutting forests may be in the initial stage of recovery with a small abundance and a fast growth rate. However, the instantaneous results of this study do not represent permanent conclusions, and we think longer-term effect of logging on tree communities and particularly logging intensity on demographic rate is still needed. We also added some of these content in the part of “Discussion” in the manuscript.

 

Point 5: I think that some more outlook would be useful for the factors influencing regeneration (e.g. the fate of seeds), let me suggest two case studies as examples:

For the amount and success of seeds, this paper might be of consideration:
https://www.jstor.org/stable/4091990?casa_token=DLoNlf9WQjEAAAAA%3A8v38IH0WAf-NB_rnh__xW6NA9Qcwq4wuyZsLPJ6R9Xiqoc4j3T-1nHKtUaBVxw8sCV_79j2BQetnu5Dmh_BJLBfa6O2Ucokl4Zc6fQ7VnnlFlEBaNA&seq=1#metadata_info_tab_contents

For various factors influencing regeneration, see this great study:
https://link.springer.com/article/10.1007/s42974-020-00021-8

Response 5：Thank you very much for your recommendation. We have added the relevant contents in the “Discussion” part of the manuscript.

 

Point 6: Avoiding edge effect is a good idea, it is acknowledged. Also, repeating the census 5 years later is a good approach. Choosing 3 * 2 locations is not too many, statistically speaking. Since vegetation sampling is not very complicated (compared to animal traps, for example), more locations could have been better, I think.

Response 6：The Hainan Bawnagling National Nature Reserve was subjected to widespread logging from the late 1950s up to 1993, and available area for establishing forest plots is very limited, especially for old-growth forest plots. Besides, we need exact logging information to conduct this study, and there are few logging records left in the Hainan Bawangling Forestry Bureau. After comprehensive consideration, we set up six, 1-ha (100 m × 100 m) forest dynamic plots, including two clear-cutting, two selectively logged and two old growth forest plots. We admit that the number of sampling replication is a little less, however, the basic patterns and differences among the three kinds of disturbed forests can be revealed with these six forest plots.

 

Point 7: line 125: there is a double-space here

Response 7：It has been deleted in the manuscript.

Point 8: line 128: do not start the sentence with "And"

Response 8：We changed the sentence to “The conservation prospects for these disturbed forests as potential habitats for Hainan gibbon were also evaluated.” in the manuscript.

Point 9: line 364, 375: "On the one hand" and "On the other hand" are very far from each other, it is hard to follow the logic. I suggest to start a new paragraph in both cases, to help the reader.

Response 9：Thanks for your suggestion. We changed this expression in the manuscript. As we suggested four possible reasons for the result, we replaced the conjunctive phrase with “Firstly, …”, “Secondly, …”, “Thirdly, …” and “Lastly, …”.

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.