Variation in the Functional Traits of Forest Vegetation along Compound Habitat Gradients in Different Climatic Zones in China

Round 1

Reviewer 1 Report

Title: Please omit ‘The’ at the beginning.

Abstract. Which region? The results presented here seems more a description of basics statistics. Please interpret results of CWM, CWV, CWS, and CWK and not simply repeat your results. For example, your results 1), 2) and 3) are basically a repetition of figures 2 to 7. You must provide a short ecological explanation for each component adding the acronym in parenthesis. When you say PC1, I assume that you performed a Principal Component Analysis. Please shortly define your statistical analyses here.

Keywords: Please do not use ‘functional traits’

Introduction: Your references 1 and 3 are out of date to say that this is a new issue in functional biogeography. What do you mean with ‘habitat filtering’? Provide a short definition in parenthesis. Where, the validation of correlations and hypothesis regarding functional traits is incomplete? In China? Worldwide? Please provide a rationale of the situation in your country and worldwide. At a first glance it seems a local issue. You need to provide a global context. What is the novelty of hypothesis 1? This is largely known. Similar comment for hypothesis 2. What do you mean with ‘certain regularities’ in hypothesis 3? Please be more specific. I am lost with the last paragraph of your Introduction, it seems more a description of Methods. Please find a proper connection. Here you say that you analyzed interactions and collinearity among the 15 biotic and abiotic variables, but then in the Methods section you say nothing. My surmise is that DHB and height are correlated to the variables CVDBH and CVCH. They are basically derived variables.

Methods: What do variables of Table 1 represent? Average of each climatic zone? Average of the corresponding plots in each climatic zone? Please check your values for temperature. You have values from 81 to 205°C. This must be a mistake. My surmise is that you must divide your data from WorldClim by 10. If you sampled forests older than 100 years, how can you have DBH of 5 to 15 cm? What do you mean with ‘positive leaves? Why you show results from your PCA here? This section is aimed at describing your methods. Percentages of PC1 and PC2 in the text are different from those in the Figures 1 and 2. Correct them. I am not clear with your statistical analyses. You used a Principal Component Analysis (PCA) to reduce multicollinearity and to capture the information in orthogonal axes. However, if you have DBH and also CVDBH in your PCA, my surmise is that you have multicollinearity between those variables. The same is for CH and CVCH. I wonder what is the ecological interpretation of CVDBH and CVCH. Could you please add information on the type of variable you have (continuous, counting, etc) to see if logarithmic transformations were appropriated. For example, you obtained CWM, CWV, CWS, and CWK for the ratio between N and P (functional trait N:P), which is a ‘percentage’. Usually percentages are transformed by the arcsine square root transformation. Similarly, in the formula of CWM you use the relative abundance, which is also a percentage. Clarify because you used CWM as the base of the other components. In the case of regressions between each component (CWM, CWV, CWS, and CWK) with each of the 6 functional traits, did you test the assumptions of normality, heterocedasticity, autocorrelation, etc?

Results: Please try to improve image resolution for Figures 1 to 10. The Y-axis of Figures 4 and 5 must be ‘Variance’ and not ‘Various’. I suggest using the abbreviated form of each component in the Y-axis. Figure 10 is very hard to understand because of low resolution and the excessive information that it contains. Find a simpler way to show these results. Also, be consistent with the variables defined in the text and the abbreviations used in Figures 1 and 2. Some of them do not coincide. For example, CH, what does it mean? Canopy height? In the text you said that you measured ‘mean height’ and in Table 1 you talk about ‘tree height’. Please be consistent with your variables. My main concern here is that you obtained a principal component (PC1) that captures 3 variables (say MAP, MAT and CVDBH). I wonder what happened with CVDBH? In the red line below figure 1 you say that positive values in the PC1 represent high temperature and precipitation, and also ‘complex community structure’. Is ‘complex community structure’ related to CVDBH? My surmise is that the coefficient of variation for DBH represents the dispersion/variation in diameter of the species and not variations in the different species. In addition, PC1 was also negatively correlated to DBH and TP. How the gradient axis captures this information? Please clarify. The same is for PC2. The red line below Figure 3 indicates that positive values of PC2 represents low soil nitrogen and high forest layer (What do you mean by ‘forest layer’?) However, the PC2 was positively related to CVH, BA, and ‘TH’ but negatively correlated to N. This is quite confusing to me and I would like you to clarify. In summary, I am not clear with your interpretation of PC1 and PC2. Is it possible that you provide more information on this point?

Discussion and Conclusions: I have no comments on these two topics as I have several doubts with statistical analyses.

I am not a native speaker but English is fine. Only minor details. 

Author Response

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Reviewer 2 Report

The manuscript presents relevant results, the results section shows all the relevant data and is well analyzed. In the discussion section it might be useful if the results can be contrasted with those of other studies, some paragraphs repeat the results with no further contextualization. 

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Round 2

Reviewer 1 Report

Please also provide the clean version of the mauscript. 

Not now

Author Response

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