Trends in Flowering Phenology of Herbaceous Plants and Its Response to Precipitation and Snow Cover on the Qinghai—Tibetan Plateau from 1983 to 2017

Round 1

Reviewer 1 Report

Jiang et al.

The authors studied the trends in flowering phenology of Herbaceous plants and its response to precipitation and snow cover on the Qinghai-Ti-betan plateau from 1983 to 2017. The introduction is well written, and the methods are fully explained. The results are demonstrated with enough curves and tables; however, the manuscript requires minor changes. Also, it will help that you mention the names instead of their abbreviations once in a while in the manuscript to remind the readers. Please see the following suggestions:

1. Use an abbreviation for “cumulative pre-season precipitation” (CPP).
2. Line 34: change “contrast with the results” to “contrast the results”.
3. Line 146: did they stop collecting snow depth data after 2013? If not, why didn’t you include it. Also, it may have been better that you use the most recent 20 years due to the climate change.
4. Increase the size of figure 2 so it can be easily seen and analyzed. Also, add day of year on the x-axis.
5. Line 237: remove “(23.1%)”.
6. Line 239: replace “(12.5%)” with “in eight early flowering species”.
7. Line 241: remove “(30.8%)”.
8. Line 243: replace “Scirpus distigmaticus and Stipa krylovii” with “two (Scirpus distigmaticus and Stipa krylovii)”.
9. Line 247: in the caption for Figure 3, change “flower date” to “flowering date”.
10. Line 250: what is “precipitaTable95”?
11. Lines 250-251: in the caption for Figure 3, change “flower date” to “flowering date”.
12. Lines 258-259: change “and the explained …. 48.0%” to “the cumulative precipitation explained 19.7-48.0% of the variation in FFD”.
13. Line 262: remove “Figure 4” at the end of the caption for Figure 5.
14. Line 264: replace “cumulative pre-season precipitation” with “CPP”. Try to use the abbreviation in the entire manuscript but as I mentioned earlier, you may mention the actual names every now and then.
15. Line 265: remove “explained variation in FFD using these models” with “R² values”.
16. Line 272: add “however” after “;”.
17. Line 273: change “FFD site” to “FFD. Site”.
18. Line 277: remove “above”.
19. In table 2, under groups use either bold or regular font for both groups.
20. Line 281: remove “46.1%”.
21. Line 285: clarify the statement “with more than the percentage of 60% to the all observed years”.
22. Figure 7: use the same maximum value for Y-axis for A, B, C, and D.
23. Line 300 (caption of Fig. 7): remove “differences between”.
24. Line 301: add “;” after (A), (B) and (C) and remove “and”.
25. Line 308: remove “whether”.
26. Figure 8 (caption): use same Y-axis maximum values for A, B, C and D.
27. Line 312: add “and” before “mid-to-late”
28. Line 313: change “analysis, for,” to “analysis for”.
29. Line 318: remove “results”.
30. Line 335: if available, solar radiation and T (air and soil) data should have been presented in tables.
31. Lines 340-361: This paragraph and figures 9, 10 should be moved to the Results.
32. Figure 9: use the same maximum for Y-axis.
33. Line 477-478: replace “we believe ……samples” with “it might be better than the small scale (controlled) studies”.
34. Line 499: replace “of plant species population changes” with “ of changes in plant species’ population”.
35. Line 524: replace “that reduced” with “that the reduced” and “not in-“ with “not the in-“.
36. Line 529: remove “with”.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript uses data collected in databases to deepen effect of precipitation and snow cover on the flowering phenology of the Qinghai-Tibetan Plateau. This wide region of China has great interest in this type of studies, also demonstrated by the large number of researches reported for this area in references chapter. Thanks to information available from meteorological database and phenology network, this study can analyze the phenological trend over a period of about 25 years (1983-2017).

As pointed out by the authors in section 4.5 "Uncertainties and implications of this study", a weakness of this work is represented by in situ monitoring of flowering phenology. Indeed, phenological data contained on database and relating to such a long period, were monitored by different people, who most likely estimated in a different way the achievement of a specific phenological phases. This introduces variation into analyzed data and adding an error term to the statistical model.

However, the statistical analysis of these data allowed to obtain information for a long period of time, for a great number of species and probably to better clarify the impact of precipitation and snow cover on the flowering phenology in QTP. The research results are a bit different from those reported in the references and obtained through experiments in controlled environment both for the QTP and for similar ecosystems in high-latitude and Arctic regions of Europe and North America. Is therefore added useful information with respect to the effects of climate change.

A lacking aspect is represented by tables and figures captions, often not self-explanatory as do not describe all parameters and elements present, and therefore should be reviewed and completed.

Line comments

L 97: replace (Figure.1) with (Figure 1);

L 108-109: Figure 1. Location of the Qinghai–Tibetan Plateau and the spatial distribution of observaTable 2. 2 Phenological and meteorological data.

- The caption “Figure 1. Location of the Qinghai–Tibetan Plateau and the spatial distribution of observa” must be rewritten including the explanation of M, PM and P stations so that it is self-explanatory;

- “2.2 Phenological and meteorological data” should be the title of the next paragraph and therefore should be sent to the next line

L 115: To know the method used to monitor flowering phenology is useful to have a term of comparison with results of other phenological study on species similar to those studied in this manuscript. Furthermore, the reference [38] is in Chinese and therefore not comprehensible to everyone. Therefore, I think it is very useful to insert a summary table with the main criteria used for the phenological monitoring or a synthetic description of these criteria on the text. A figure with pictures of different monitored phases may also be useful.

L 247: To improve the caption by explaining that size and color of the dots indicate the different FFD trend.

L 250-252: “Figure 4. The overall trends in first flower date and cumulative pre-season precipitaTable 95. confidence interval of the overall trends in first flower date and precipitation. ***: P < 0.001; **：P < 251 0.01; *: P < 0.05.”

To correct the caption text and also to explain what the pink dotted line means;

L 262: “Figure 5. Relationship between first flower date and cumulative pre-season precipitation Figure 4“

To correct the caption text and also to better explain parts A and B of Figure 5.

L 278-279 and L 318-320: to specify in the caption the meaning of d.f and F

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

General comments

The authors present trends in flowering phenology of herbaceous plants under recent climate change. I appreciate the efforts that the authors have put into this research. The study area (Qinghai-Tibetan Plateau) is very interesting and it is certainly a very naturally valuable mountain and alpine ecosystem. The paper is well written and the structure is also very good. The authors attempt a very original approach, but their data capabilities are severely limited. I think that with the presented database of phenological observations of herbaceous plants it is not realistic to fulfill the intended goals of this paper.

Specific comments

- Table 1 Geographical coordinates, elevation and observed species at the 27 phenological stations on the Qinghai-Tibetan Plateau.

 The database represents 27 phenological stations often with incomparably differentiated ecological conditions. However, not a single botanical species connects all 27 phenological stations. For example: Taraxacum mongolicum recurs at 18 stations out of 27, the highest score. Iris lactea Pall is repeated at only 7 stations, ... Leymus secalinus, Poa annua, P. alpina are represented only once out of 27 stations.

The authors differentiate the observed plants into two major groups "Two types of flowering mechanisms on the QTP: preformation and vernalization-induced floral organ growth". But they do not work further with this division. 

The authors differentiate the observed plants into two major groups "Two types of flowering mechanisms on the QTP: preformation and vernalization-induced floral organ growth". But they do not work further with this division. 

The authors differentiate the observed plants into two major groups "Two types of flowering mechanisms on the QTP: preformation and vernalization-induced floral organ growth". But they do not work further with this division. 

The authors differentiate the observed plants into two major groups "Two types of flowering mechanisms on the QTP: preformation and vernalization-induced floral organ growth". But they do not work further with this division. 

The authors have created two additional groups for phenological analysis:

- early flowering series

- mid-to-late-flowering series

It is logical, therefore, that the authors have obtained highly ambiguous results.

Another problem is that the authors do not indicate in the text which specific meteorological station and precipitation station they used for the phenological stations listed in Table 1.

On page 5 (row 142) the authors write "Daily average air temperature data from 1980 to 2017 for 19 stations ...." and "Daily snow depth (SD) data were also acquired from 1961 to 2013 at 102 stations" (row 145).

How did the authors deal with such data inhomogeneity?

What was the distance and elevation of meteorological and precipitation stations related to each of the 27 phenological stations?

I assume that the precipitation station also measured snow depth and vice versa. Since Figure 1. gives information about the stations only superficially and the reader can only guess what M stations mean. PM stations, P stations.

It is wrong to use temporally inhomogeneous periods of phenological observations, meteorological data, precipitation and snow data for such an analysis.

The question is, in what form did precipitation (rain or snow) occur during the course of the FFD in each of the years studied? In the case of snow, the water may not have reached the plant roots (sublimation, snow drift etc. )

The authors in section 2.1 Study area mention extremely different climatic conditions of the OTP. e.g. "annual mean precipitation decreases from 1764 mm in the southeast to 16 mm in the northwest" as well as "annual mean air temperature decreases from 15.5°C in the southeast to -5.0°C in the northwest" I have the opinion that if the authors want to find out what are the phenological manifestations of the plants they should create several smaller and climatically more homogeneous ecological sub-regions. Logically, they would also get groups with comparable plants and their phenological responses.

 

 

Author Response

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Author Response File: Author Response.pdf