Multistage Sampling and Optimization for Forest Volume Inventory Based on Spatial Autocorrelation Analysis

Round 1

Reviewer 1 Report (Previous Reviewer 1)

This paper applies geostatistics to improve the sampling efficiency of forest inventory in China’s Sichuan Province. They demonstrate that a multi-stage sampling scheme that focuses on maximizing spatial correlation of plots resulted in estimates that had high accuracy and precision, compared to sampling the full 20% panel of plots each year. This work has important implications for increasing efficiency of forest inventory where certain situations demand it - such as a global pandemic that restricts transportation and lodging, or where financial and personnel resources are limited.

 

I read both prior versions of the manuscript, and I see progress towards a paper that is readable and compelling. However, more editing is required. Throughout the paper, there are sentences that are very general and not specific enough to communicate the ideas that the authors are trying to get across. A good example of this is the first sentence in the Abstract. Below, I provide some line-by-line comments that are examples of places in the writing that need to be improved; however, this list is not exhaustive, and I recommend thoroughly editing the entire paper to improve the grammar and structure.

 

Line comments:

13: This abstract is missing a justification for your research.

14: “the tool” is not specific enough. 

17: Delete “each of the”.

30: It is not clear what is meant by “lower” - do you mean that the second stage estimation is more accurate than the continuous forest inventory estimation?

38-41: This sentence does not make sense as written - try “because it effectively reduces the sample size”

45: Do not use the same word twice with two different meanings in the same sentence. Instead of “acquired by means of inventories”, you can say “acquired using inventories”.

69: Define the abbreviation (“CFI”) the first time you use it.

75-77: This sentence is hard to read and it is not clearly connected to the sentence before it or to the one after it. Consider rewriting or reorganizing this section of the paragraph.

84-89: This sentence is too long and has many grammatical errors. Change to ”research on sampling techniques is focused on… data, applied using various approaches.”

90-91: I disagree with this topic sentence - it was not made apparent when each is appropriate. Not many examples were provided.

122-126: This is the place in the Introduction where you must introduce the specific problem that you are trying to solve in a compelling way. Instead, these few sentences wander around the issue and the reader is left guessing what the actual problem is.

128: Instead of starting off with what you did, start with why you did it. Something like “we used geostatistics to help guide a sampling strategy that would reduce the number of plots to be measured while maintaining a high degree of accuracy and precision.” That way, you communicate the intent and methods in the same phrase.

166: Were there separate tree volume models by species?

170-171: This statement is too general. List the software company and version and the names of the specific tools that were used.

184-185: This is an odd sentence and it is incomplete. This is a description of a tool copied and pasted from https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-statistics/incremental-spatial-autocorrelation.htm

Instead, lead off with “We used the Incremental Spatial Autocorrelation tool to…” and then paraphrase from the manual instead of copying it verbatim.

295-297: This statement seems like it belongs more in the Discussion than in the Results.

309-314; 325-330; 341-346; 361-366: These paragraphs all report values in the same repetitive way; the writing could be more efficient if these values were instead added to the respective Tables that are referenced. Then, the paragraphs could be deleted.

Figure 6 is not particularly helpful - ask yourself what is the main point you would like to get across, and is there another way to do it?

389-391: This sentence is hard to understand - do you mean that the accuracy is best with the cluster sampling?

398-411: This paragraph presents no results. Did you mean to put it in the Discussion?

429-448: This is not a good paragraph to end the Discussion with. It does not connect well with the findings of your study. Please rewrite.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report (Previous Reviewer 2)

I noticed that this is a re-submitted manuscript, and the authors have properly solved my concerns in the revision response, so I think this is acceptable and have no more suggestions.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This paper uses several different sampling strategies for forest inventory plots to estimate forest volume across the Sichuan Province, China. These strategies are all based on results from a spatial autocorrelation analysis of plots sampled from 2002 through 2017. All strategies maintained high accuracy of forest volume estimates, and even the strategy with the lowest number of plots sampled still had high accuracy at 93%.

Overall, I found this paper was difficult to read and comprehend. The Introduction is hard to follow and does not make a compelling case for the research. In addition, it spends too much time describing the history of geostatistics, which is unnecessary for this paper. The Methods are missing an important part, which is how the forest volume is calculated at the plot level. It instead jumps straight to the spatial autocorrelation calculations. The Results were a bit easier to understand, and the figures and tables helped tell the story of the different sampling strategies. The Discussion was as difficult to follow as the Introduction, with no main take-home points emphasized.

I suggest that the authors work on re-writing the paper for clarity to better emphasize the motivation and most important conclusions of this work.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

 

This is a manuscript dealing with forest resource inventory policy. I consider it to be meaningful and can further improve the accuracy of the national forest inventory.  Some concerns should be properly solved.

1. The use of annual estimates in this paper is not appropriate, and the results part only shows the five-year interval estimates rather than consecutive year estimates.

2. The formula needs to be interpreted with the corresponding subscript, e.g., Eq(4) what is the meaning of ‘RU’?

3. Line 152, average carbon storage should be revised.

4. The discussions and conclusions should be separated into separate parts.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This manuscript reads a little better than the first version that I read. The writing must be improved, and the Methods and Discussion still lack information that would make this work more scientifically sound.

Below, please find my line-by-line comments. Most of these comments are intended to help improve the quality of the writing.

 

11: This is a very generalized statement that not all would agree with – tree volume tells us nothing about tree density or stand age, for example.

14-16: “we used…” for what purpose?

18: It is unclear what is meant by “different methods” – were different methods used to create each of the 5 groups? Or were different methods then used with each of the groups for further sampling?

20: This sentence is unclear: Did the analysis of the sampling efficiency compare two different methods: generalized estimation and probability sampling?

22-23: “there is a substantial positive spatial autocorrelation” at what distances?

37: It helps when the abstract ends with one main conclusion – what is it that you want your readers to take away?

43-44: Again, this sentence implies that forest volume is the only important variable – which is untrue.

54: What is meant by “real-time”? I think you mean “annual”. Please be more specific.

57: The first time an abbreviation is presented, please spell it out (CFI).

63-65: This sentence is not compelling – “is necessary” why?

68: “in certain situations” – like what? Please provide examples.

75-76: The meaning is unclear here – “all show annual and comprehensive development” – the techniques are being developed? This is an odd concluding statement in this paragraph.

80-91: I still do not think this adds to the Introduction. Most readers will already have a vague familiarity with geostatistics, so only a brief definition needs to be provided. The connection to soil science, water research, and ecology is not needed here and does not strengthen the paper. Further, there should be many references in the literature of forestry applications of geostatistics that are not referenced here – please find these and cite them.

101: Is there a citation for the “1/5+4/5” joint estimation approach?

104: “quite large” – provide a number

105: This sentence is hard to understand – what is meant by “lack of pertinence exists”? Please reword.

107: “connectivity” – do you really mean “correlation”?

115: “Updated the dates” – this is unclear. What dates?

150: You must provide a reference for the tree volume models used for each species. Also, provide more detail about the variable of interest – is this volume of live trees? Or live and dead? What are the scientific units of volume?

152: Please provide more contexst for the use of the Moran index. Why is this being calculated, and how will it be analyzed as part of the scientific question?

163: Please provide more information about the “incremental spatial autocorrelation tool”.

166: Please see my comment on line 152.

175: “evenly divided” – please provide more detail on how this was done.

186: Please provide more information on how the spatial stratification worked.

226-227: “trend increase” should be “increasing trend and then decreasing”

227: “According to the results” is not necessary.

346: “goodness” is a bit value-laden – try something else here.

356: “human interference” – what is meant by this?

375-376: “According to the results” – instead, use “We found that”

377-379: This is an ineffective concluding sentence for this paragraph. Instead, think of a way to summarize the most important implications of your finding stated in the previous sentence.

368-399: This discussion is really too short – there must be more that can be said about the study’s findings. Please think about the wider-reaching implications of this study.

Figures: I would combine Figures 3, 4, and 5 into a single figure.

Add some more information to the figure captions. “Figure 2. Spatial clustering pattern of forest volume for each of the 4 panel years” or something like that.

Author Response

Please see the attachment.

Author Response File: Author Response.docx