Stand Characteristics Rather than Soil Properties Contribute More to the Expansion of Moso Bamboo (Phyllostachys edulis) into Its Neighboring Forests in Subtropical Region

Round 1

Reviewer 1 Report

Question 1: Moso bamboo is a native bamboo species originating in China. The long-term evolution has formed its characteristics of monopodial bamboo, which is the result of natural selection. The unconstrained expansion of moso bamboo into adjacent woodlands and negative effects on the function services of forest ecosystem should be seen as the result of natural competition, and the impact between trees is relative. Moso bamboo would not be a problematic species if not for human influence and intervention. We should imitate nature, take advantage of the natural attributes of moso bamboo, give full play to its advantages, and change the problem to be beneficial to the production and life of human beings.

Question 2: There are massive data obtained from the expansion characteristics of moso bamboo and the properties of stand structure and soil for 58 bamboo-woodland interfaces, and redundancy analysis is conducted to find the relationship between the variables of bamboo expansion and the properties of interfaces. Valuable and interesting results are obtained, the results of data analysis for consecutive years would be more convincing.

Question 3: I think that soil properties also have an important influence on the expansion of moso bamboo. Further, the climate, altitude, site conditions (slope, aspect, area of original bamboo forest, etc.) of each recipient forest cannot be ignored.

Question 4: Note the correct use of relevant abbreviations, such as SoC should be SOC

Question 5: In line 93-94, the reference should be provided.

Question 6: In line 103, the sentence should be rephrased.

Question 7: In line 147-150, why did the relevant indexes of soil properties measure only 0-30cm?

Question 8: In line 216, the “dramatical” should be “dramatic”.

Question 9: In line 231, the “was” should be “were”.

Question 10: In line 339, the subsection title should be rewritten.

Question 11: The literature published in last 3 years should be supplemented.

Question 11: As the human disturbance activities (eg. bamboo shoot harvest, thinning) are the key factors affecting the extent of bamboo expansion. In order to show the relationship between disturbance and bamboo expansion, fixed sample plots and control experiments should be set up, and long-term observations should be performed.

Author Response

Question 1: Moso bamboo is a native bamboo species originating in China. The long-term evolution has formed its characteristics of monopodial bamboo, which is the result of natural selection. The unconstrained expansion of moso bamboo into adjacent woodlands and negative effects on the function services of forest ecosystem should be seen as the result of natural competition, and the impact between trees is relative. Moso bamboo would not be a problematic species if not for human influence and intervention. We should imitate nature, take advantage of the natural attributes of moso bamboo, give full play to its advantages, and change the problem to be beneficial to the production and life of human beings.

Response: Agree and accepted! On one hand, moso bamboo is a valuable economic species, on the other hand, it is an invasive species capable of expanding into the secondary forests damaged by human beings. In other words, the expansion of moso bamboo has double sides. It is favorable for the areas where the harvest activities are permitted, but unfavorable in natural reserves whose purpose is to protect biodiversity. We should take reasonable measures to deal with moso bamboo in the light of local conditions, such as controlling its expansion behavior in the nature reserves, and encouraging its expansion in areas like derelict and mining land.

Question 2: There are massive data obtained from the expansion characteristics of moso bamboo and the properties of stand structure and soil for 58 bamboo-woodland interfaces, and redundancy analysis is conducted to find the relationship between the variables of bamboo expansion and the properties of interfaces. Valuable and interesting results are obtained, the results of data analysis for consecutive years would be more convincing.

Response: Totally agree. It is time-consuming and labor-intensive to investigate the expansion of bamboos in as many as 58 interfaces across Jiangxi province. We have planned to monitor the dynamic expansion of bamboos consecutively. Unfortunately, due to some unexpected reasons, we have been only carrying out consecutive monitoring in only a portion of interesting interfaces. in Guanshan Nature Reserve, Dagang Forestry Station, and Qiyunshan Nature Reserve etc. (see Fig. 1). At present, we only have systematically collected these field data of all 58 interfaces, which are reported in this paper. No further results of later consecutive monitoring are available at present since we have not completely obtained.

Question 3: I think that soil properties also have an important influence on the expansion of moso bamboo. Further, the climate, altitude, site conditions (slope, aspect, area of original bamboo forest, etc.) of each recipient forest cannot be ignored.

Response: Agree. The results of RDA in this study showed that forest stand features account for 58.8% of the expansion of moso bamboo, while the soil characteristics and their interactions accounted for 14.3%. The soil water was significantly negative with the expansion of moso bamboo. We assumed that the lack of significant differences in soil properties among recipient forests may be responsible for the low influence of soil properties for bamboo expansion. As you mentioned that the other measured factors, such as altitude, slope, aspect or/and other nutrients, play certain roles in explaining the bamboo expansion.

Question 4: Note the correct use of relevant abbreviations, such as SoC should be SOC

Response: Accepted. We have revised the abbreviations of full text carefully.

Question 5: In line 93-94, the reference should be provided.

Response: Accepted. The references “Guo et al., 2004; Song et al., 2017” regarding to the bamboo expansion were added in new Line 102.

Question 6: In line 103, the sentence should be rephrased.

Response: The sentence has been written as “These findings will be essential to achieve a better understanding on the mechanism of bamboo expansion into neighboring forests, thus help make pertinent management decisions of moso bamboo forest especially in natural reserves”.

Question 7: In line 147-150, why did the relevant indexes of soil properties measure only 0-30cm?

Response: Thank you very much. The depth of soil layer we measured is mainly because that most of rhizomes and roots for moso bamboo are located in 0-30 cm of soil. The characteristic of this depth of soil more easily affected the expansion of bamboo expansion.

Question 8: In line 216, the “dramatical” should be “dramatic”.

Response: Agreed. We have rewritten the “dramatical” into “dramatic” in new line 269.

Question 9: In line 231, the “was” should be “were”.

Response: Agreed. We have made the change accordingly. Please see line 294.

Question 10: In line 339, the subsection title should be rewritten.

Response: Accepted. The subsection title was written as “Effects of the characteristics of stand and soil on bamboo expansion”.

Question 11: The literature published in last 3 years should be supplemented.

Response: The recent researches were added in new line 52-53, line 401-402.

Question 12: As the human disturbance activities like bamboo shoot harvest and thinning are the key factors affecting the extent of bamboo expansion. In order to show the relationship between disturbance and bamboo expansion, fixed sample plots and control experiments should be set up, and long-term observations should be performed.

Response: Agree and accepted! As you suggest that the disturbance is one of key reasons affecting moso bamboo expansion. The controlling experiments including three treatments (regulating the canopy closure of invaded ecosystems, thinning the density of bamboos, harvesting bamboo shoots) were carried out in sites of Qiyunshan, Jinggangshan, and Dagang sites. Through long-term observations of these experiments, we want to know the underlying effects of disturbance activities on the expansion process of moso bamboo.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,  

This paper analyzed the key factors that influence the extent of moso bamboo expansion in the subtropical region. The study design and the results obtained are clear and worthy of publication in the journal. However, there are some points that are unclear, mainly in the methodology. After I understand the M&M fully, I will read on and add comments.    

 

Main comments  

・Please write the year and period of the survey. And I did not understand how many years the expansion was evaluated for each plot.  

 

・ L159　I do not understand how to calculate "Expansion distance" (purpose 1 of this paper). As long as the rhizomes are not excavated, it is also problematic to assume that the new culm is connected to the nearest mother culm. Is this different from the method of Bai et al. 2016?　Provide more clarification based on previous studies.

 

  ∙ Please describe how authors evaluate "Disturbance". I am not sure which period of time and to what extent authors are considered as "disturbance". From reading L419-430, I imagined authors were considering a longer period than one or two years, is that understanding correct?

 

  ∙ A review of relevant papers is essential to the value of this study. The following literature should be read to strengthen the intro and discussion. For example, the following reference pointed to the importance of adjacent forest vegetation structure as the key factor in determining the extent of moso bamboo expansion.

Kobayashi et al. (2018) A simple method to estimate the rate of bamboo expansion based on one-time measurement of the spatial distribution of culms. Ecol. Res. 33(6)    

 

Other comments  

・L45-54: The information on bamboos in general and information on bamboos with leptomorphous rhizomes are mixed. Since this paper focuses on the characteristics of bamboo spreading by rhizomes, please describe the two in an organized manner so that they are not mixed up.

・Did authors check to see if they could pool and analyze the 13 sites?

・I think the CaC in Table 2 is correct without units, not %.  

・Is there any possibility of animal influence including wild boar on the rate of expansion?

Author Response

We appreciate the thoughtful comments and valuable suggestions of the anonymous reviewers as relates to how we might improve the manuscript. We have addressed the comments carefully in our revised manuscript. Should there be any questions regarding our responses, we will be pleased to address them more fully.

This paper analyzed the key factors that influence the extent of moso bamboo expansion in the subtropical region. The study design and the results obtained are clear and worthy of publication in the journal. However, there are some points that are unclear, mainly in the methodology. After I understand the M&M fully, I will read on and add comments.

Response: Thanks for the valuable suggestions. We have taken into account all comments and all questions in the revised text.

Main comments

Question 1: Please write the year and period of the survey. And I did not understand how many years the expansion was evaluated for each plot.

Response: The expansion of moso bamboo is a long-term process. In the summer (June to August) of 2017 and 2018, this work was carried out to monitor the characteristics of bamboo expansion in 58 interfaces of 13 sites across Jiangxi province using the space-for-time substitution method. Although this work is one-time survey, the plots we established are numerous and distributed widely. The results can objectively reflect the relative contribution of properties of stand and soil on the expansion of bamboo expansion.

Question 2: L159 I do not understand how to calculate "Expansion distance" (purpose 1 of this paper). As long as the rhizomes are not excavated, it is also problematic to assume that the new culm is connected to the nearest mother culm. Is this different from the method of Bai et al. 2016? Provide more clarification based on previous studies.

Response: Agreed. As the rhizomes are not excavated, we can’t know the moving distance of bamboo forest into adjacent through measuring the increment of extending rhizomes. Since the new culms are easily recognized in forests, and their growth are mainly supported by the mother bamboos (age>1). The expansion distance of this study was calculated as the linear distance between the new culm to its nearest mother culm, which is different from the method of Bai et al. 2016. Because the study of Bai is a continuous observation of 10 years in one site, our study is a one-time measurement of 13 sites. The method of Bai cannot be used in our study. In fact, this measurement method of our study has underestimated the expansion distance of moso bamboo, but it can still reflect the rate of bamboo expansion.

Question 3: Please describe how authors evaluate "Disturbance". I am not sure which period of time and to what extent authors are considered as "disturbance". From reading L419-430, I imagined authors were considering a longer period than one or two years, is that understanding correct?

Response: Agreed. The expanded woodlands are defined as disturbance forests according to these characteristics: (1) the canopy closure is 0.1~0.5; (2) the density of stand is 0~20 ind/100 m²; (3) the plant species is mainly donimanted by the deciduous trees, with number ratio of deciduous tree to evergreen tree more than 1. (4) the top of trees are broken down by human activities or natural disasters. If the forests have these features, we considered them as disturbed forests.

Question 4: A review of relevant papers is essential to the value of this study. The following literature should be read to strengthen the introduction and discussion. For example, the following reference pointed to the importance of adjacent forest vegetation structure as the key factor in determining the extent of moso bamboo expansion.

Kobayashi et al. (2018) A simple method to estimate the rate of bamboo expansion based on one-time measurement of the spatial distribution of culms. Ecol. Res. 33(6)   

Response: Agreed. Relevant papers including Kobayashi et al. (2018) are added to strengthen in introduction and discussion section in line 52-53, 401-402.

Other comments 

Question 5: L45-54: The information on bamboos in general and information on bamboos with leptomorphous rhizomes are mixed. Since this paper focuses on the characteristics of bamboo spreading by rhizomes, please describe the two in an organized manner so that they are not mixed up.

Response: Accepted. The specific information of bamboo with leptomorphous rhizomes was discriminated from the bamboo in general in line 47-56.

Question 6: Did authors check to see if they could pool and analyze the 13 sites?

Response: Yes. We used different methods to check the experimental data to ensure that all the data are in line with the analysis conditions. For example, the correlation processing of spatial heterogeneity among 13 sites, independent T-test to detect the differences of variables of bamboo expansion and so on.

Question 7: I think the CaC in Table 2 is correct without units, not %.

Response: Agreed. We have made the change accordingly. Please see Table 2.

Question 8: Is there any possibility of animal influence including wild boar on the rate of expansion?

Response: Good idea! Besides the properties of stand structure and soil we measured, the rate of bamboo expansion can be affected by other environment factors. As you suggested that the animal influence is one of potential factors affecting bamboo expansion. In field, we found that animals such as rabbit and boar often feed with bamboo shoots. However, how many bamboo shoots are fed by animals is still known. In future, we can assess the effects of animal feeding on the bamboo expansion.

 

Round 2

Reviewer 2 Report

Thank you for answering in detail. Now that I understand the method, I read it again and pointed out the following issues.

・I am very questionable whether you can estimate the expansion of bamboo forests properly by using the method. Based on your reply, I understood that the expansion distance was defined by the difference in distance between the new culm and the nearby older culm. According to this definition, the expansion distance is always positive even when new culms grow on the pure bamboo side of the forest. This is not a realistic "expansion" because it ignores the direction of transition of the bamboo forest as a whole. I think it is appropriate to determine the direction of expansion (positive or negative) and calculate how much the expansion front can be updated within that direction, as addressed in previous studies (e.g., Bai et al. 2016 and Okutomi et al. 1996). It might be desirable to calculate the difference between the average position of new culms and that of old culms based on the culm position information (here, new culms: 1-2 year old considering the 2 year cycle). I suggest strongly that you revise and recalculate, as the results will not be so different. 

L282-283 I think there is an assumption that there is a transition from deciduous forest to evergreen forest in the secondary succession series in this area. This needs to be clearly stated.

L291 If each plot has only been surveyed once, I think it should be "describe" or "record", not "monitor".

L485 I think you agree with my previous point, so add stochastic effects such as wildlife and human interference.

Author Response

Dear Reviever

    We would thank for the valuable suggestions of reviewer. We have taken into account all comments and all questions in the revised text.

    Please see the attachment.

    We looking forward to hearing from you.

    Kind regards.

Author Response File: Author Response.docx