Elevational Gradient of Climate-Driving Effects on Cropland Ecosystem Net Primary Productivity in Alpine Region of the Southwest China

Round 1

Reviewer 1 Report

This manuscript describes experiments that relate changes in climate to NPP in alpine regions of SW China. I have several suggestions for improvement in addition to the specific recommendations given below. First, it would be very helpful to provide information about cropping systems in this alpine area.  There are lots of numbers and maps, but there is no information at all about what is actually grown in these areas. Second, the authors need to provide a rationale for using a model that yields NPP numbers that differ very significantly from NPP numbers obtained from ground measurements.  The difference is mentioned, but it is disregarded.  A 29% error rate between expected and observed is a lot, and so the authors need to provide a convincing rationale for disregarding it. Third, and as noted below, the authors tend to make general, often unsubstantiated and sometimes speculative statements instead of the specifics that they should include. Fourth, the authors need to explicitly indicate how this work has added to the body of knowledge about NPP in alpine areas.  What is truly new, and why is it important.  This never really comes out.  In this respect, the Conclusions Section is very disappointing—there are no conclusions based on the research findings treated in this manuscript.

L41/42.  It is sufficient to write 34.5% and 12.6% (or even 35% and 13%).  No need to go down to hundredths of one percent when making general statements like this.  The same argument holds for L50 and other parts of the manuscript.

L54/55.  There is something missing here.  I don’t think you mean to state that decreased NPP has caused a large area of grain production.  Maybe affected a large area of grain production?  Not sure what you mean.

L59. Start a new paragraph with the word At—you are beginning to express a new thought at this point.

L74. How do climate driving….

L76/77. This question is the same as No. (2).  You use different words, but in both cases, you are asking about the effect of elevation on climate driving effects.  

Figure 1.  This figure and the text describing it could be improved.  You should add a map of China that indicates the location of your study area (particularly helpful for Western readers).  L80/81 names the four provinces and directs the reader to Figure 1, but the provinces are not identified in the figure (the outlines are there, but that is all).  It is never a good idea to tell readers to find information in a figure when the information is not there.  Some of the letters in the first panel are very hard to read, especially when they are over the brown background.  Can you use other colors to make the letters more visible?  It would also be helpful to add a sentence or two to refer to Figure 1b (this panel is never referred to in the text).  You should also explain the information about carbon content, which is given in the figure but also never discussed—include the source of these data.  Also, you use 1,000 m as the minimum elevation for alpine land in your study (L128).  Is alpine defined the same way in Figure 1b?  Or does the source of this information use another threshold?

L110/113. There are serious grammatical errors in this sentence—“caused by that the, also, which were the actual…).  Also, you should give a short description of how the field survey data were obtained.  More importantly, a 29% error is quite high—it means that your simulated NPP data differ significantly from what is happening on the ground.

Figure 2.  The legend of this figure is incomplete.  The three lines need to be explicitly identified, and one of the lines needs to be related to the square symbols.

L132. …which resulted in inclusion of …. in the study.

L138.  Suggest that you relabel this section as Statistical Analysis or Statistical Methods.  Section 2.3 also has methods in it, so it is incorrect to just label this section Methods.

L153. The figure shows.  You should use present tense here and in introducing the other illustrative material.

L155.  Here again, you are adding nonsignificant digits to the right of the decimal point, i.e. 751.97 implies that there is difference between 751.96, 751.97, and 751.98. This is equivalent to an inconsequential 10 mg per square meter—and not significant.  See L162 and L164 for other examples. 

L156. To south and west.

L170/171. Consider as a title: Relationship between spatial….NPP and climate factors.

L239/240.  It is unclear what you mean by unimodal pattern.  Figure 2 clearly shows that NPP increases and then decreases with increasing elevation, a pattern which does not appear to be “unimodal.”  Please explain.

L242/243.  You are discussing hundredths of a degree difference in annual precipitation and tens of micrometers of difference in annual precipitation.  See earlier comment about significant figures.

L246. How is a “medium temperature” defined?  And how do you know that a “medium temperature” exists between 1600 and 2600 m in the study area?  Can you be more precise and provide evidence for these statements?

L262/264.  Similar in what ways?  Did these previous studies also deal with alpine areas with a similar climate?  Be more specific.

L273/274. This is a general, speculative statement. Can you be more specific and provide any supportive evidence?

L275. Start a new paragraph at When.

L282. Is a reminder that.

L292. Maybe, “It has been shown that significant climate warming trends can enhance…”

L305. I do not understand your argument that “soil microbial community” is a stronger ecosystem property.  Please elaborate.

L309/334. This very long, detailed paragraph has little to do with the alpine region and should be considerably shortened.  It tends to divert attention away from the high elevation study area.

Conclusions section.  Most of this section is a summary rather than an integrative analysis of the data and what they mean. Conclusions are mentioned in the last two sentences, but these statements are very general and not dependent on any of the work that was done. These “conclusions” are really the rationale for starting the research, not the result of any new knowledge that came from the research.

 

 

 

 

 

 

Author Response

This manuscript describes experiments that relate changes in climate to NPP in alpine regions of SW China. I have several suggestions for improvement in addition to the specific recommendations given below.

 

Point 1: First, it would be very helpful to provide information about cropping systems in this alpine area.  There are lots of numbers and maps, but there is no information at all about what is actually grown in these areas.

 

Response 1: Following the reviewer’s suggestion, we added information about cropping systems in alpine region of the southwest China in section 2.1.

 

Point 2: Second, the authors need to provide a rationale for using a model that yields NPP numbers that differ very significantly from NPP numbers obtained from ground measurements.  The difference is mentioned, but it is disregarded.  A 29% error rate between expected and observed is a lot, and so the authors need to provide a convincing rationale for disregarding it.

 

Response 2: Following the reviewer’s suggestion, we added method of our field survey in section 2.2. Then we explained reasons of the difference between simulated NPP data and field survey data in validation section, and moved the validation section to result section following reviewer2’s suggestion.

 

Point 3: Third, and as noted below, the authors tend to make general, often unsubstantiated and sometimes speculative statements instead of the specifics that they should include.

 

Response 3: Following the reviewer’s suggestion, we revised our manuscript and took further analyses. Itemized responses to comments 5-29 are appended below.

 

Point 4: Fourth, the authors need to explicitly indicate how this work has added to the body of knowledge about NPP in alpine areas.  What is truly new, and why is it important.  This never really comes out.  In this respect, the Conclusions Section is very disappointing—there are no conclusions based on the research findings treated in this manuscript.

 

Response 4: Following the reviewer’s suggestion, we rewrote our conclusion section, and clarified our importan findings explicitly.

 

Point 5: L41/42.  It is sufficient to write 34.5% and 12.6% (or even 35% and 13%).  No need to go down to hundredths of one percent when making general statements like this.  The same argument holds for L50 and other parts of the manuscript.

 

Response 5: Following the reviewer’s suggestion, we revised all percent numbers in our manuscript.

 

Point 6: L54/55.  There is something missing here.  I don’t think you mean to state that decreased NPP has caused a large area of grain production.  Maybe affected a large area of grain production?  Not sure what you mean.

 

Response 6: Following the reviewer’s suggestion, we revised the sentence to “Increasing in extreme weather events such as high temperature and seasonal anomaly in precipitation has caused severe damage to cropland ecosystem NPP in these areas resulting in a large area of grain production decline”.

 

Point 7: L59. Start a new paragraph with the word At—you are beginning to express a new thought at this point.

 

Response 7: Following the reviewer’s suggestion, we started a new paragraph.

 

Point 8: L74. How do climate driving….

 

Response 8: Following the reviewer’s suggestion, we revised the question to “Did climate driving effects on cropland ecosystem NPP vary between different elevations?”.

 

Point 9: L76/77. This question is the same as No. (2).  You use different words, but in both cases, you are asking about the effect of elevation on climate driving effects.  

 

Response 9: Following the reviewer’s suggestion, we revised the question to “When we investigated climate driving effects on cropland ecosystem NPP across the entire study area, could the results be different from question 2?”.

 

Point 10: Figure 1.  This figure and the text describing it could be improved.  You should add a map of China that indicates the location of your study area (particularly helpful for Western readers).  L80/81 names the four provinces and directs the reader to Figure 1, but the provinces are not identified in the figure (the outlines are there, but that is all).  It is never a good idea to tell readers to find information in a figure when the information is not there.  Some of the letters in the first panel are very hard to read, especially when they are over the brown background.  Can you use other colors to make the letters more visible?  It would also be helpful to add a sentence or two to refer to Figure 1b (this panel is never referred to in the text).  You should also explain the information about carbon content, which is given in the figure but also never discussed—include the source of these data.  Also, you use 1,000 m as the minimum elevation for alpine land in your study (L128).  Is alpine defined the same way in Figure 1b?  Or does the source of this information use another threshold?

 

Response 10: Following the reviewer’s suggestion, we revised figure 1. First, we added a map of China that indicated the location of our study area in figure 1a. Second ,we added names of four provinces in figure 1a-d. Third, we used light red to label landform in figure 1a. Fourth, we added two sentences to describe cropland distribution and our field suvey data in figure 1b.

 

Point 11: L110/113. There are serious grammatical errors in this sentence—“caused by that the, also, which were the actual…).  Also, you should give a short description of how the field survey data were obtained.  More importantly, a 29% error is quite high—it means that your simulated NPP data differ significantly from what is happening on the ground.

 

Response 11: Following the reviewer’s suggestion, we revised the sentence to “The field survey data was the actual carbon assimilation amount of cropland ecosystem. The actual carbon sequestration amount was derived from ecosystem NPP minus heterotrophic respiration and external disturbances.”, and explained reasons of the difference between simulated NPP data and field survey data.

 

Point 12: Figure 2.  The legend of this figure is incomplete.  The three lines need to be explicitly identified, and one of the lines needs to be related to the square symbols.

 

Response 12: Following the reviewer’s suggestion, we added description of the three lines.

 

Point 13: L132. …which resulted in inclusion of …. in the study.

 

Response 13: Following the reviewer’s suggestion, we revised the sentence to “which resulted in inclusion of elevation bins from 1000 m ASL to 4500 m ASL in the study”.

 

Point 14: L138.  Suggest that you relabel this section as Statistical Analysis or Statistical Methods.  Section 2.3 also has methods in it, so it is incorrect to just label this section Methods.

 

Response 14: Following the reviewer’s suggestion, we revised the section title to “Statistical methods”.

 

Point 15: L153. The figure shows.  You should use present tense here and in introducing the other illustrative material.

 

Response 15: Following the reviewer’s suggestion, we revised the sentence to “The figure shows……”. We also revised all the same cases in the manuscript.

 

Point 16: L155.  Here again, you are adding nonsignificant digits to the right of the decimal point, i.e. 751.97 implies that there is difference between 751.96, 751.97, and 751.98. This is equivalent to an inconsequential 10 mg per square meter—and not significant.  See L162 and L164 for other examples. 

 

Response 16: Following the reviewer’s suggestion, we revised all annual NPP values in our manuscript.

 

Point 17: L156. To south and west.

 

Response 17: Following the reviewer’s suggestion, we revised the sentence to “The cropland ecosystem NPP increased from east and north to south and west”.

 

Point 18: L170/171. Consider as a title: Relationship between spatial….NPP and climate factors.

 

Response 18: Following suggestions of reviewer1 and reviewer2, we divided the result section to six parts to clearly distinguish validation, elevational gradient of NPP, interannual change trends in NPP across the entire study area, elevation gradient of interannual change trends in NPP, climate driving effects on NPP change across the entire study area, elevational gradient of climate driving effects on NPP change.

 

Point 19: L239/240.  It is unclear what you mean by unimodal pattern.  Figure 2 clearly shows that NPP increases and then decreases with increasing elevation, a pattern which does not appear to be “unimodal.”  Please explain.

 

Response 19: Following the reviewer’s suggestion, we revised the sentence to “Cropland ecosystem NPP converted from increasing to decreasing along increasing elevations in alpine region of the southwest China”.

 

Point 20: L242/243.  You are discussing hundredths of a degree difference in annual precipitation and tens of micrometers of difference in annual precipitation.  See earlier comment about significant figures.

 

Response 20: Following the reviewer’s suggestion, we revised all annual precipitation values in our manuscript.

 

Point 21: L246. How is a “medium temperature” defined?  And how do you know that a “medium temperature” exists between 1600 and 2600 m in the study area?  Can you be more precise and provide evidence for these statements?

 

Response 21: Following the reviewer’s suggestion, we added sentences to describe elevational gradient of mean annual temperature and indicated that “The medium temperatures existed between 1600-2600 m ASL, which was located in the central part of Yunnan Province. Its mean annual temperature was between 10.11-15.35 oC”. We then introduced mean annual temperature below 1600 m ASL (15.64-15.91 ^oC) and above 2600 m ASL (below 10 ^oC) in the paragraph.

 

Point 22: L262/264.  Similar in what ways?  Did these previous studies also deal with alpine areas with a similar climate?  Be more specific.

 

Response 22: Following the reviewer’s suggestion, we compared our results with previous studies about cropland ecosystem NPP and climate change in southwest China or its alpine region.

 

Point 23: L273/274. This is a general, speculative statement. Can you be more specific and provide any supportive evidence?

 

Response 23: Following the reviewer’s suggestion, we rewrote this section. First, we took this paragraph after discussions about “Along increasing elevations, increasing cropland ecosystem NPP …… was driven by climate warming from negative at low elevations to positive at high elevations”. We then revised the sentences to “The elevation-dependent effect of climate warming on increasing NPP and elevational gradient of cropland distribution led to different results when we analyze climate driving effects on cropland NPP at different spatial scales. Cropland area percentages were much larger at low elevations than at high elevations (appendix A1). The distribution of cropland and the negative driving effect of climate warming on cropland ecosystem NPP at low elevations brought about nonsignificant negative impact of climate warming on increasing NPP across the entire study area”.

 

Point 24: L275. Start a new paragraph at When.

 

Response 24: Following the reviewer’s suggestion, we started a new paragraph and revised the new paragraph to be more clearly.

 

Point 25: L282. Is a reminder that.

 

Response 25: Following the reviewer’s suggestion, we revised the sentence to “This finding is a reminder that……”.

 

Point 26: L292. Maybe, “It has been shown that significant climate warming trends can enhance…”

 

Response 26: Following the reviewer’s suggestion, we revised the sentence to “It has been shown that significant climate warming trends can enhance……”.

 

Point 27: L305. I do not understand your argument that “soil microbial community” is a stronger ecosystem property.  Please elaborate.

 

Response 27: Following the reviewer’s suggestion, we revised the sentence to “Alpine ecosystem has to develop stronger ecosystem properties, such as foliar nitrogen content, to cope with harsh environment at high elevations. Soil microbial community also aggregates cold shock, nitrogen cycling and sulfur cycling genes to adapt cold environment at high elevations. The stronger ecosystem and soil properties caused that cropland was more sensitive to climate warming at high elevations than at low elevations”.

 

Point 28: L309/334. This very long, detailed paragraph has little to do with the alpine region and should be considerably shortened.  It tends to divert attention away from the high elevation study area.

 

Response 28: Following the reviewer’s suggestion, we deleted redundant discussions to make this paragraph to be more concisely and clearly.

 

Point 29: Conclusions section.  Most of this section is a summary rather than an integrative analysis of the data and what they mean. Conclusions are mentioned in the last two sentences, but these statements are very general and not dependent on any of the work that was done. These “conclusions” are really the rationale for starting the research, not the result of any new knowledge that came from the research.

 

Response 29: Following the reviewer’s suggestion, we rewrote our conclusion section. We strengthened our findings about elevational gradient of climate driving effects on cropland ecosystem NPP, and pointed out that we should take the elevational gradient of climate driving effects into account when we manage food security to deal with ongoing climate change in alpine region with complex topography.

Reviewer 2 Report

The authors present statistical analysis of trends in time of NPP and climate variables (Ta, P, solar radiation) in the alpine region of southwest China.

 

Unfortunately, the structure of the manuscript is poor, making it hard to follow the analysis and the extract the outcome. Numbers in the manuscript generally are given with a very high number of decimals; the authors should consider whether the analyses justify this.

 

p2, L72: "how does climate change ... change" change to "how does climate ...  change"

p2, L74: do you mean how climate driven effects in NPP change with hight or do you mean how do the climatic drivers change with height (which would be the same as the second question in (1)) ?

p2, L76: unclear wehat is meant here

ch 2.2: The description of the model is fine here. But the comparison with the fielddata (which is not described at all in the manuscript) would belong to the result section imho. If I understood this right you compared NPP (model) with NEE (from EC measurements?) Wuld it be possible to compare it to NPP directly? Is there any consequence from the comparison study for your further analyses?

 

ch 2.3: would take this before the model data and include the "field survey data" used to "validate" the model

Result section: The result section is in general hard to read. Clearly devide between changes in height in climatic drivers, temporal trends in climatic drivers, and temporal trends in changes in height in climatic drivers. Same for NPP. This is already done according to the chapter headings, but it could be clearer in the written text (maybe by extending the wording from e.g. "slopes" to what exactly is described or vary the wording to describe what the statistics mean).

Figure 5: add explanation of stars (indicating significant trend?) to figure caption

ch3.3: rewrite. NPP is mainly driven by solar radiation which fits to the main result.

Chapter 4:

p9, L265: "significant positive correlation with climate drying". But trends in precipitation were mostly not significant

p10, L322: how did you define drought? How does it relate to your analysis

ch5:

The conclusion are rather general, missing to give the direction of e.g. the "elevation-dependent pattern".

 

Author Response

The authors present statistical analysis of trends in time of NPP and climate variables (Ta, P, solar radiation) in the alpine region of southwest China.

 

Point 1: Unfortunately, the structure of the manuscript is poor, making it hard to follow the analysis and the extract the outcome. Numbers in the manuscript generally are given with a very high number of decimals; the authors should consider whether the analyses justify this.

 

Response 1: Following the reviewer’s suggestion, we revised structure of result and discussion to make these two sections to be more clearly. Moreover, we revised all annual NPP values and annual precipitation values in our manuscript.

 

Point 2: p2, L72: "how does climate change ... change" change to "how does climate ...  change"

 

Response 2: Following the reviewer’s suggestion, we revised "how does climate change ... change" to "how did climate ...  change".

 

Point 3: p2, L74: do you mean how climate driven effects in NPP change with hight or do you mean how do the climatic drivers change with height (which would be the same as the second question in (1)) ?

 

Response 3: Following the reviewer’s suggestion, we revised the question to “Did climate driving effects on cropland ecosystem NPP vary between different elevations?”.

 

Point 4: p2, L76: unclear wehat is meant here

 

Response 4: Following the reviewer’s suggestion, we revised the question to “When we investigated climate driving effects on cropland ecosystem NPP across the entire study area, could the results be different from question 2?”.

 

Point 5: ch 2.2: The description of the model is fine here. But the comparison with the fielddata (which is not described at all in the manuscript) would belong to the result section imho. If I understood this right you compared NPP (model) with NEE (from EC measurements?) Wuld it be possible to compare it to NPP directly? Is there any consequence from the comparison study for your further analyses?

 

Response 5: Following the reviewer’s suggestion, we added method of our field survey in section 2.2. Then we moved the validation content to result section.

 

Point 6: ch 2.3: would take this before the model data and include the "field survey data" used to "validate" the model

 

Response 6: Following the reviewer’s suggestion, we added method of our field survey in data section, and then took the data section before the NPP model section.

 

Point 7: Result section: The result section is in general hard to read. Clearly devide between changes in height in climatic drivers, temporal trends in climatic drivers, and temporal trends in changes in height in climatic drivers. Same for NPP. This is already done according to the chapter headings, but it could be clearer in the written text (maybe by extending the wording from e.g. "slopes" to what exactly is described or vary the wording to describe what the statistics mean).

 

Response 7: Following the reviewer’s suggestion, we rewrote this section. First, we divided the result section to six parts to distinguish validation, elevational gradient of NPP, interannual change trends in NPP across the entire study area, elevation gradient of interannual change trends in NPP, climate driving effects on NPP change across the entire study area, elevational gradient of climate driving effects on NPP change. Moreover, we revised "slopes" to “trends”.

 

Point 8: Figure 5: add explanation of stars (indicating significant trend?) to figure caption

 

Response 8: Following the reviewer’s suggestion, we added explanations of stars in figure caption.

 

Point 9: ch3.3: rewrite. NPP is mainly driven by solar radiation which fits to the main result.

 

Response 9: Following the reviewer’s suggestion, we rewrote this section to clarify the main driving factor of solar radiation (see line 268-269). Moreover, we compared different results between analysing at different spatial scales (i. e. climate driving effects on NPP change across the entire study area, driving effects of climate factor trends on NPP trends of all elevation bins, climate driving effects on NPP change at each elevation bin) in the study, and discussed reasons of the different results in discussion section (see the third and fifth paragraphs in discussion section).

 

Point 10: Chapter 4: p9, L265: "significant positive correlation with climate drying". But trends in precipitation were mostly not significant

 

Response 10: Following the reviewer’s suggestion, we discussed reasons of the different results between analyzing across the entire study area and at each elevation bin (see the third and fifth paragraphs in discussion section).

 

Point 11: p10, L322: how did you define drought? How does it relate to your analysis

 

Response 11: Following the reviewer’s suggestion, we revised the sentence to “During 2000-2017, more than 10 times of drought were tracked in the two parts by Self-calibrating Palmer Drought Severity Index”.

 

Point 12: ch5: The conclusion are rather general, missing to give the direction of e.g. the "elevation-dependent pattern".

 

Response 12: Following the reviewer’s suggestion, we rewrote our conclusion section. We strengthened our findings about elevational gradient of climate driving effects on cropland ecosystem NPP, and pointed out that we should take the elevational gradient of climate driving effects into account when we manage food security in alpine region.

Reviewer 3 Report

This study presents interesting results about the role of climate variability in NPP changes in SW China. It is a welcomed contribution to RS. I have the following comments that can improve the readability of the manuscript. 

 Keywords shall be not the replication of words in the title.

-      A key limitation of this study is that it ignores the possible role of different variables (e.g. soil moisture, global warming, basin morphometric characteristics, dam construction, etc.) that may affect the response of cropland ecosystem net  primary productivity (NPP). These possible limitations should be elaborated thoroughly at least in the discussion section.

-       Another key limitation is that the authors have not considered the different responses of vegetation as a function of their types/classes, irrespective of elevation. All these issues need further discussion in the text.

-     I think the selection of 1000 m as a threshold for defining alpine region seems to be a relaxed threshold. The rationale behind  selecting this threshold should be clarified.

-       Also, what is the rationale behind selecting these specific three climatic parameters as drivers of NPP variability.

-       How was the statistical significance of trends in NPP tested? This should be clarified in the methodology section.

-       I am wondering why the datasets used in this study have not been updated for more recent years.

-       Figure 2: It is important to provide a more comprehensive description of how the dependent and independent variables were computed.

 

-        The description of the meteorological data is quite poor (spatial and temporal resolution, quality, etc.). An important aspect is related to the density of raw data. How did this density vary as a function of elevation? This is a critical aspect to guarantee the reliability of the obtained results.

Author Response

This study presents interesting results about the role of climate variability in NPP changes in SW China. It is a welcomed contribution to RS. I have the following comments that can improve the readability of the manuscript. 

 

Point 1: Keywords shall be not the replication of words in the title.

 

Response 1: Following the reviewer’s suggestion, we revised our keywords to "food security; climate change; alpine region with complex topography".

 

Point 2: A key limitation of this study is that it ignores the possible role of different variables (e.g. soil moisture, global warming, basin morphometric characteristics, dam construction, etc.) that may affect the response of cropland ecosystem net  primary productivity (NPP). These possible limitations should be elaborated thoroughly at least in the discussion section.

 

Response 2: Following the reviewer’s suggestion, we added discussions about influences of foehn effect in dry-hot river valleys and soil moisture on cropland ecosystem at low elevations below1700 m ASL (see line 328-334). Furthermore, we discussed influences of dam construction on changing characteristics of hydrological cycle in discussion section (see line 382-385).

 

Point 3: Another key limitation is that the authors have not considered the different responses of vegetation as a function of their types/classes, irrespective of elevation. All these issues need further discussion in the text.

 

Response 3: Following the reviewer’s suggestion, we added influences of cropland types on climate driving effect in discussion section (see line 378-381).

 

Point 4: I think the selection of 1000 m as a threshold for defining alpine region seems to be a relaxed threshold. The rationale behind  selecting this threshold should be clarified.

 

Response 4: Following the reviewer’s suggestion, we clarified that “Following previous studies [33, 34], we defined areas above 1000 m above sea level (ASL) as alpine region” in section 2.2.

 

Point 5: Also, what is the rationale behind selecting these specific three climatic parameters as drivers of NPP variability.

 

Response 5: Following the reviewer’s suggestion, we clarified that “Based on results of previous studies about climate driving effects on cropland ecosystem NPP [29, 36, 37], we selected three factors in the study, i. e. temperature, precipitation, solar radiation”.

 

Point 6: How was the statistical significance of trends in NPP tested? This should be clarified in the methodology section.

 

Response 6: Following the reviewer’s suggestion, we clarified that " The statistical significance of the linear regression slope was determined from the p-value of a two-tailed Student’s t test " in section 2.4.

 

Point 7: I am wondering why the datasets used in this study have not been updated for more recent years.

 

Response 7: Following the reviewer’s suggestion, we clarified that the NASA VIP data “was updated to 2014 when we run our model” in section 2.2. Even now, there is no latest update.

 

Point 8: Figure 2: It is important to provide a more comprehensive description of how the dependent and independent variables were computed.

 

Response 8: Following the reviewer’s suggestion, we added descriptions of how the dependent and independent variables were computed in figure caption.

 

Point 9: The description of the meteorological data is quite poor (spatial and temporal resolution, quality, etc.). An important aspect is related to the density of raw data. How did this density vary as a function of elevation? This is a critical aspect to guarantee the reliability of the obtained results.

 

Response 9: Following the reviewer’s suggestion, we added description of the meteorological data, including raw data and interpolation method (see line 126-134). Moreover, we compared climate change in the study with previous studies in discussion section to guarantee the reliability of the obtained results (see line 303-315).

Round 2

Reviewer 3 Report

The authors have responded adequately to the comments raised in the earlier revision. I believe that the manuscript can be accepted for publication in its latest form.