Inventory of China’s Net Biome Productivity since the 21st Century

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors:

This is an interesting paper dealing with the problem of the spatial distribution pattern of NBP in China. And the author has done a lot of work. The paper is also relevant in the context of climate change, which is the greatest global environmental challenge of the 21st century. However, there are some problems in this paper. 1. The paper has problem with language and accuracy of terms. Some parts are difficult to follow. A thorough editing will improve it and make it easier for the reader to go through.  2. This paper has no innovation in methods or models.  3. The accuracy of the results is uncertain, and the range of deviation is not given. It is unknown to what extent the results in this paper can be trusted.  4. The analysis of driving force in this study is insufficient.

1. The authors should pay more attention to the English language. For example, Line43-46; Line55-57; Line64-65; Line154-155…

2. Line62-64 This statement is not accurate. Is there any research on NBP? If not,      where do the data [18, 29-33] come from?

3. Line96 How to get the formula?

4. Line 164-165 Whether the statement makes sense? is there no data or not change at      all?

5. Line 167-169Figure 1 does not contain the names of provinces, which are hard to follow in international journals. Also for figure 2

6. Line195 “Time evolution” --> “Temporal evolution”

7. Line 245 (part 4.1) The differences between the emissions of forest diseases, agricultural production activities and NMVOC and the existing results have been calculated respectively, but an overall result has not been given. In general, the calculation error or floating range of this study has not been specified.

8. Line 302 “specialization” If this word is appropriate?

9. Line307 (part4.2) is not a good explanation for the heterogeneity of the NBP, also reason of the phenomenon of line174-L189 in 3.2 are not well explained, either.

10. Line 307-310 Hard to follow.

11. Line324“carbon consumption” --> “carbon emission”

12. Line322 What do you mean for “science”?

 

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Author Response

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Reviewer 2 Report

The manuscript "Inventory of China's net biome productivity since the 21st century" by Du et al. aims to integrate multi-source data and evaluate the response mechanism of China's net biome productivity to natural and human processes from 2000 to 2018.

 

My main concern is the lack of specificity on the data origin. Specifically, the fluxes of emissions from reactive carbon and animal ingestion, from human factor disturbances, and from natural disturbances. The reference is very vague and not informative. How were the data filtered and added to the model?

 

Additionally, the term "eddy correlation" denotes the mass, heat, and momentum flux densities across a plane at a point in a turbulent flow. This is not presented in the manuscript; thus, the use of this term is not appropriate. 

 

The authors need to justify the decision to average the values by administrative units, is this ecological relevant? Otherwise, this decision must be reflected in the objective, title, and throughout the document. This way of presenting the results is not wrong but needs to be justified (for example, province policies, stakeholders, etc.). 

 

Fig. 2 Figure caption point letters for the different panels; however, these letters are missing in the panels; please add. The maps also show a box, but its usefulness is not clear (no zooming); see also fig. 5.

Author Response

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Reviewer 3 Report

The authors present an estimate of NBP to provide a more nuanced view of terrestrial carbon sink or source across China for the period 2000 – 2018. There are major elements the paper that the authors must address. These include, how the authors’ approach differs from the presented NBP literature estimates and why these estimates are more robust. Secondly, the accounting methodology is not clear or detailed enough. Thus, the results are a bit meaningless without a more nuanced, detailed, and thorough review and explanation of the components and methods behind all if not many of the estimators that determined NBP

 

Line 15: The authors might consider being more definitive, NBP is a more scientific measure of ecosystem carbon sink

Line 35: ground? And underground change to belowground

Line 40: NEP is used to measure what indicator of terrestrial ecosystems?

Line 41: not necessarily, it just means NPP is greater than Rh, which does not mean the ecosystem as a whole is a net carbon sink. If you assume otherwise, please define the components of  NEP you are referencing. The authors mention in “undisturbed” ecosystems, Stead-state ecosystems rarely exist unless it is over short temporal scales, which then is a very narrow definition of NEP. I would consider revising this approach to NEP it is not a robust way of using it.

Line 49: Can the authors also address NECB and if or why their use of NBP differs from that? And how temporal dynamics influence the metric used.

Line 63: If there are already NBP estimates, how does tis paper differentiate or intend to improve on these estimates. What approach do the authors implement that should make the reader believe your estimates at the end are more robust. This is missing from the Introduction.

Line 88: It is best to define the components of NEP, being more specific than “uptake or emission”. Because  as defined here NEP is inferred from MAT and MAP, thus how do the authors ensure that the components of carbon flux like rat respiration or pest respiration are not already integrated into the regression estimate, since Rh is a component of NEP and Rh is calculated from an estimate of NEE, how are non-soil organismal respiration rates being excluded. The authors need to be much more specific and through in their explanation of the underlying methodology in the component estimates

Line 94: What is meant by we quantified? Did the authors conduct the regression analysis? Where did the coefficients originate from?

Line 114: these should be introduced in the same order as presented in equation 4

Line 118 and 119: The authors have to be very explicit as to why these components are not somehow already integrated into the NEP equation estimator. Without having a clear explanation of the NEP estimator, this is largely unknown here.

Line 123: What is “is the carbon depletion flux of terrestrial ecosystems caused by forest disease”?

Line 125: Why only rats and not all non-soil organismal respiration?

Line 127: (this entire section) Are there no estimates of harvest across any scale for the study region? Or are the authors suggesting that they are not only estimating the carbon flux associated with harvest, but then the lifecycle of that carbon (e.g., the “carbon consumption”); because what is meant by the “carbon consumption”. If lifecycle is entering into the carbon balance equation of NBP, then the authors are not using NBP in the traditional definition sense and are reporting something akin to Net Forest Sector Carbon Balance (when reporting forest harvest with an LCA) See Tara W Hudiburg et al 2019 Environ. Res. Lett. 14 095005. This needs addressing

Line 144: The authors mention earlier in the Methods Section using the fire area dataset, but there is no indication how fire emissions were derived.

Author Response

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Reviewer 4 Report

The current work by Du et al, estimated the magnitude of NBP in 31 Chinese provinces (except Hong Kong, Macau, and Taiwan) from 2000 to 2018, and clarified its temporal and spatial evolution. The results confirmed that net biome productivity (NBP) is a more scientific measure of net carbon sink than net ecosystem productivity (NEP). This study is beneficial to provide data support for the realization of China's carbon neutrality goal and global carbon cycle research. Overall, the manuscript should be revised before publication publishing. 

 

Some points for the authors to consider and discuss further are as follows:

1. The paper exist many detail issues, including punctuation marks, title order, measurement units, clarity and consistency of figures, references, etc., please check carefully. Furthermore, please thoroughly copyedit your manuscript for language usage, spelling, and grammar.

 

2. What are the segmentation bases of annual average NEP/ NBP, annual average NEP/NBP changing trend, average annual carbon release of FE_RCCI/FE_AD/FE_ND in Figure 1-3?

 

3. There are no data to support some results, including line 152-153 “From 2000 to 2018, China's annual average NEP was 1.06 Pg C yr^-1 (equivalent to 153 3.886 Pg CO₂ yr^-1)”, line 213-217 “In the past 19 years, the NEP has been 1.06 Pg C yr^-1. The utilization of agricultural, forestry and grass products consume 70% of NEP. In addition, natural disturbances such as animal husbandry, volatile organic compound emissions, fire, water erosion and wind erosion consume 10% of NEP. Finally, the total amount of NBP is 0.212 Pg C yr^-1 and increases at the rate of 0.19 Tg C yr^-1” and so on. Kindly present these results with graphs or tables.

 

4、The description of result is very puzzling and inconsistent with the figures 1-3. Kindly clarify in the manuscript.

 

5、Line 164-“NEP remains basically unchanged in regional concentration distribution”, what does this mean?

 

6. Kindly provide references/citations for “Relevant scholars advocate the use of net

biome productivity (NBP) as an indicator to measure the carbon sink level of terrestrial

ecosystems” and “In addition, forest diseases and insect pests are an important component affecting the carbon consumption of natural ecosystems”.

 

7. Discussion was written a bit like results and conclusions. Further discussion is needed.

 

 

8. Towards the end of discussion section, kindly add a paragraph about the potential applications and meanings of this study.

Author Response

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Round 2

Reviewer 1 Report

 1 : A thorough editing will improve it and make it easier for the reader to go through.

For example, Line55-61 ：Lack of predicate verbs

Zhang et al [27] China's agricultural carbon emissions from the 20th century. Fang et al [28] the carbon content released from the forest ecosystem by forest product utilization was estimated. Zhang et al [29] the effects of grazing intensity and topography on the carbon exchange capacity of desert grassland were studied. In recent years, quantitative assessment of terrestrial ecosystem carbon budget has become an important basis for regional climate control and carbon sink management [30, 31].

2. Figure1. You mean Liaoning province，right？LL?--> LN

 

 

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Reviewer 2 Report

No further comments

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Reviewer 4 Report

I am glad that the author can answer my questions well, but there are still many problems，such as :

1: The paper still exist many detail issues, such as clarity and size of figures, references formation, etc., please check the full paper carefully. Furthermore, the manuscript still needs to be corrected for grammatical and typological errors. 

 

2: The description of “Result” is very puzzling and inconsistent with the figures 1-3. Kindly clarify in the manuscript.

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