Stochastic Processes Drive Plant Community Assembly in Alpine Grassland during the Restoration Period

Round 1

Reviewer 1 Report

 

Thank you for inviting to review this interesting manuscript dealing with a very current and interesting topic. Data from a long-term experiment yield very valuable results.

Some similar projects focus primarily on monitoring species richness (taxonomic diversity) and changes in the structure of grasslands exposed to different habitat conditions and types of management. In this manuscript, also changes in phylogenetic diversity were studied. Could the authors explain in more detail what additional value monitoring of phylogenetic diversity brings to our knowledge?

In discussion, the authors say: “….we found that different pasture managements had no significant effect on species richness, phylogenetic diversity, and phylogenetic structure across the altitudinal gradient:” This is a generalizing statement and I think, that types and intensity of management should be discussed in more details.

The authors conclude that ‚For local grazing management, it should be better to relieve the burden of high grazing intensity by reducing the number of livestock below 4700 m, while keeping the current grazing intensity or adding a little bit more pressure above 4700 m in this study area.‘ Isn't this too bold recommendation? Isn't this a risk to the biodiversity of communities growing at higher altitudes? The authors did not have the opportunity to study areas at an altitude above 4700 m, which would be more heavily effected with grazing. So how can they justify their recommendations?

I have also several technical comments to this manuscript:

Fig. 1 – I don't understand why the authors decided to choose this way of presenting their results. A pie diagram seems to be a bit confusing to me. In any case, names plant speciea and familieas are poorly rediable. Bigger fonts should be used.

Fig. 2,3 – The same scales shoudl be used for pair figures (enclosure/grazing). Asterisks and labels are poorly visible, bigger fonts are necessary.

I am not a native speaker, but I believe that a careful check of the language would improve a quality of this paper siginicantly.

In addition, there are various formal deficiencies in the text, careful editing is necessary. For example: Fig S3 vs. Fig. 6a are used - I assume that Fig. (with ".") should be used consistently throughout the text.

The authors should also further unify the use of ‘Fig’ and’ Figure’. Both forms are used randomly in the text, which is certainly not correct.

Author Response

Question 1 Some similar projects focus primarily on monitoring species richness (taxonomic diversity) and changes in the structure of grasslands exposed to different habitat conditions and types of management. In this manuscript, also changes in phylogenetic diversity were studied. Could the authors explain in more detail what additional value monitoring of phylogenetic diversity brings to our knowledge?

Reply: Thanks very much for the valuable question. We have added related explanation in the part of methods. Please go to page 4 Line 157: “Phylogenetic diversity (PD) has been considered to be a predictor of ecosystem functioning as conserved traits of ecological niches [50] and represents the evolutionary potential of a species setting against environmental changes [51]. Nowadays, PD has been increasingly considered as a strategy to identify geographical regions with max-imum diversity and resilience to climatic fluctuations [52,53]. Therefore, to evaluate the total evolutionary history of the species in an assemblage, Faith’s PD was used and calculated by ape and picante package.”

50. Gravel, D.; Bell, T.; Barbera, C.; Combe, M.; Pommier, T.; Mouquet, N., Phylogenetic constraints on ecosystem functioning. Nat. Commun. 2012, 3, 1117.
51. Forest, F.; Grenyer, R.; Rouget, M.; Davies, T. J.; Cowling, R. M.; Faith, D. P.; Balmford, A.; Manning, J. C.; Procheş, Ş.; van der Bank, M.; Reeves, G.; Hedderson, T. A. J.; Savolainen, V., Preserving the evolutionary potential of floras in biodiversity hotspots. Nature. 2007, 445(7129), 757–760.
52. Faith, D.P., Phylogenetic Diversity: Applications and Challenges in Biodiversity Science. Springer International Publishing; 2018.
53. Miller, J.T.; Jolley-Rogers, G.; Mishler, B.D.; Thornhill, A.H., Phylogenetic diversity is a better measure of biodiversity than taxon counting, J. Syst. Evol. 2018, 56 (6), 663–667.

 

Question 2 In discussion, the authors say: “….we found that different pasture managements had no significant effect on species richness, phylogenetic diversity, and phylogenetic structure across the altitudinal gradient:” This is a generalizing statement and I think, that types and intensity of management should be discussed in more details.

Reply: Thanks for the suggestion. We have added a new Figure S1 to show the plots distribution along the slope. Also, the site of resident settlement around 4500 m were shown on the map, which means the grazing intensity is heavier at lower altitudes compared with that at higher ones. Related description can be found on page 3 Line 119-124:“As the only pure animal husbandry county in Lhasa, the capital of Tibet, Dangxumg County is rich in grassland resources (about 70% of the total area is grassland). Due to the high quality and vast area of grassland, the number of yak and sheep in this county reached 2.837×10⁵ and 2.215×10⁵ in 2017, respectively. In our study area, the resident settlement sits at the lower altitudes (Figure S1) where the grazing intensity is much greater than at higher altitudes.”.

 

Question 3 The authors conclude that‚ for local grazing management, it should be better to relieve the burden of high grazing intensity by reducing the number of livestock below 4700 m, while keeping the current grazing intensity or adding a little bit more pressure above 4700 m in this study area. Isn't this too bold recommendation? Isn't this a risk to the biodiversity of communities growing at higher altitudes? The authors did not have the opportunity to study areas at an altitude above 4700 m, which would be more heavily affected with grazing. So how can they justify their recommendations?

Reply: Thanks for the question. We have revised the corresponding description accordingly. Please go to page 14 Line 473：“For local grazing management, it should be better to relieve the burden of high grazing intensity by reducing the number of livestock below 4700 m, while keeping the current grazing intensity above 4700 m in this area.”

 

Question 4 Fig. 1 – I don't understand why the authors decided to choose this way of presenting their results. A pie diagram seems to be a bit confusing to me. In any case, names of plant species and families are poorly radiable. Bigger fonts should be used.

Reply: Thanks for this valuable suggestion. We have redesigned Figure 1 into a dendrogram phylogenetic tree with larger fonts.  

 

Question 5 The same scales should be used for pair figures (enclosure/grazing). Asterisks and labels are poorly visible, bigger fonts are necessary.

Reply: In this version, we have modified Figure 2 and 3 accordingly.

 

Question 6 I am not a native speaker, but I believe that a careful check of the language would improve a quality of this paper significantly.

Reply: Thanks for the suggestion. We have gone through the whole text, and tried our best to check the logic and grammar mistakes. Hope this works at this stage.

 

Question 7 In addition, there are various formal deficiencies in the text, careful editing is necessary. For example: Fig S3 vs. Fig. 6a are used - I assume that Fig. (with ".") should be used consistently throughout the text. The authors should also further unify the use of ‘Fig’ and’ Figure’. Both forms are used randomly in the text, which is certainly not correct.

Reply: In this version, instead of using the omitted forms, we use “Figure” throughout the whole text.

Author Response File: Author Response.docx

Reviewer 2 Report

Diversity-1922813-peer-review

This rarely undertaken topic of research is very interesting due to the need to protect the global biodiversity with the use of moderate management. The manuscript is well written and can be accepted in Diversity after minor revision; a some remarks are listed below:

1. More detailed information in the introduction or the methodology on the treatments used in the grassland restoration would be useful (about the enclosures).

2. Figure 1. ‘Different colored circles indicate 210 species that occur at different altitudes, blank circles indicate absence, and solid circles indicate 211 presence during the survey. The different colors of the species fields indicate to which family these 212 species belong.’ –  the figure is very useful, but this caption is completely incomprehensible, please add a colored legend clearly explaining all of altitude, species and families scales (gradients) presented at this ‘mandala’.

3. Figures 7 and S1. Charts should be larger to be easier to read.

4. The discussion could be a bit shortened and simplified, especially with more detailed considerations.

5. Conclusions - presenting them in the form of compact points would allow the reader to better understand the results of the research.

Author Response

Question 1 More detailed information in the introduction or the methodology on the treatments used in the grassland restoration would be useful (about the enclosures).

Reply: Thanks for the suggestion. We have strengthened this part in Methods, please go to page 3 Line 119 “As the only pure animal husbandry county in Lhasa, the capital of Tibet, Dangxumg County is rich in grassland resources (about 70% of the total area is grassland). Due to the high quality and vast area of grassland, the number of yak and sheep in this county reached 2.837×10⁵ and 2.215×10⁵ in 2017, respectively. In our study area, the resident settlement sits at the lower altitudes (Figure S1) where the grazing intensity is much greater than at higher altitudes.” And page 3 Line 144: “In September 2006, we set up a 20m×20m fence at each of the six altitudes below 5200 m (Figure S1). All the fences were set near the automatic weather stations mentioned above. At 5200 m, large-sized fence was not used due to very low grazing intensity.”

 

Question 2 Figure 1. ‘Different colored circles indicate 210 species that occur at different altitudes, blank circles indicate absence, and solid circles indicate 211 presence during the survey. The different colors of the species fields indicate to which family these 212 species belong.’ –  the figure is very useful, but this caption is completely incomprehensible, please add a colored legend clearly explaining all of the altitude, species, and families scales (gradients) presented at this ‘mandala’.

Reply: In this version, we have redesigned Figure 1 into a dendrogram phylogenetic tree. The elements mentioned above have been added. Please go to page 6 Line 210：“Figure 1. The phylogenetic distribution of all plants in this study. Different colored circles indicate species that occur at different altitudes, blank circles indicate absence, and solid circles indicate presence during the survey. The different colors of the branches correspond to different families in the legend”.

 

Question 3 Figures 7 and S1. Charts should be larger to be easier to read.

Reply: Thanks, and we have enlarged these charts. Please go to page 10 for Figure 7 and page 19 for Figure S1.

 

Question 4 The discussion could be a bit shortened and simplified, especially with more detailed considerations.

Reply: Thanks for the suggestion. We have revised accordingly. E.g., the 2^nd and 4^th paragraph in discussion has been shortened.

 

Question 5 Conclusions - presenting them in the form of compact points would allow the reader to better understand the results of the research.

Reply: Thanks for the suggestion. This part has been shortened in a way rather than compact them into points. Please go to page 13 Line 462: “We found that the overall phylogenetic structure of the alpine grassland community was divergent at medium and high altitudes (4800-5100 m) where the environment was relatively unextreme. At the lower altitudes (4400-4650 m) with low precipitation, and the highest altitude (5200 m) with low temperature, the phylogenetic structure of the plant community was more aggregative. It seemed that the grassland management exerted little impact on all the diversity and structure indices. Among the environmental factors, precipitation was the dominant factor affecting these indices. Stochastic processes have driven the changes in the communities between inside and outside the fences.”

Author Response File: Author Response.docx