A Review of Terrestrial Carbon Assessment Methods Using Geo-Spatial Technologies with Emphasis on Arid Lands

Round 1

Reviewer 1 Report

MS: A Review of Terrestrial Carbon Assessment Methods Using Geo-Spatial Technologies with Emphasis on Arid Lands

The topic of this article is interested to a border community of forestry and geo-spatial sciences. Although ‘arid lands’ given as the major keyword in the title, the research finding and rational for the research to the specific topic is limited. For example, I could not see literature support for carbon assessment on arid lands in the introduction (L 33-143), only L 125 and flowchart given the term. The introduction described border ideas on carbon footprints in terms of forestry (L 34-94) and a paragraph (L95 – 101) given for remote sensing and GIS aspect. The statistical analysis is lacking the article and lot of discussions on carbon sequestration in terms on forestry. This is a remote sensing journal, which should focus the remote sensing aspect of the study. The remote sensing contributions are limited to data, sensors, and indices. The article is suitable for GIS related journal instead of remote sensing, but if authors interested in remote sensing journal, the article need restructuring with intensive remote sensing applications.  

Here is an example:

H Nguyen, T., Jones, S., Soto-Berelov, M., Haywood, A., & Hislop, S. (2020). Landsat Time-Series for Estimating Forest Aboveground Biomass and Its Dynamics across Space and Time: A Review. Remote Sensing, 12(1), 98.

More specific comments are given as follows:

Abstract

The abstract is the lacking on methods

Keywords: sequestration – lowercase

Introduction

Authors discussed wide topics like forest biomass, carbon sequestration, policies, mapping biomass in the introduction. But I did not see relevant literature supported for the main topic ‘arid land’ carbon assessment in the introduction.

L 75 Check with journal guidelines whether author, year citation (Eggleston et al. (2006)) or Eggleston et al. [17] citation applicable.

L 120: Why begin with section 2, where is section 1?

L 130: Figure 2 is the workflow, which has to move to the methods

L 167 (1934) no need the year, just reference [31]

Table 1: why two lines for component and one line for calculation method. Can be formatted as:

3 Litter/ Debris 10-20% of Above-ground biomass [30]

L 192-193 Remove year from references and add the reference number in parenthesis. Refer authors instruction

L 205 (2005)

L 213 (2006)

L 222 (2014)

L 229 [11-12, 19,35]

Table 2: Are all those references related to remote sensing aspect or forestry?

L 243 in-situ

L 265 CS studies ‘and’ lowercase. Caption needs a sentence on what those numbers refereeing in the graph

L 276 Do you really need a Figure to display those results? The findings can summarize using two sentences.

L 278 Table 3 has some information which can easily find (i.e. temporal resolution, swath, cost etc.). Therefore, replacing those columns with examples of articles and major topics will be helpful.

L 285 Hebbar [ ]

L 287 3 years

L 298 (1993)

L 359: Object-based Image Analysis

L 388 Rosema et al. [ ]

L 392 Morel et al.[ ]

L 404 The Figure redrawn from one reference [97], /however it’s good to have come up a model compiling several articles.

L 419 Ten et al. [ ]

L 427 (2003)

L 495 [55] why several

Fig. 8 a. axis not labeled

L 524 Missing Axis label

L 560 X axis is percentage?

 

 

 

Author Response

Response to Reviewer 1 Comments

 

 

Point 1:

• The topic of this article is interested to a border community of forestry and geo-spatial sciences.
• Although ‘arid lands’ given as the major keyword in the title, the research finding and rational for the research to the specific topic is limited. For example, I could not see literature support for carbon assessment on arid lands in the introduction (L 33-143), only L 125 and flowchart given the term. The introduction described border ideas on carbon footprints in terms of forestry (L 34-94) and a paragraph (L95 – 101) given for remote sensing and GIS aspect.
• The statistical analysis is lacking the article and lot of discussions on carbon sequestration in terms on forestry.
• This is a remote sensing journal, which should focus the remote sensing aspect of the study. The remote sensing contributions are limited to data, sensors, and indices. The article is suitable for GIS related journal instead of remote sensing, but if authors interested in remote sensing journal, the article need restructuring with intensive remote sensing applications. Here is an example: “H Nguyen, T., Jones, S., Soto-Berelov, M., Haywood, A., & Hislop, S. (2020). Landsat Time-Series for Estimating Forest Aboveground Biomass and Its Dynamics across Space and Time: A Review. Remote Sensing, 12(1), 98”.

 

Response 1:

• While this paper can certainly be of interest to the border community of forestry and geo-spatial sciences, we target primarily the community interested in the application of Geo-spatial technologies (Remote Sensing & GIS) to the assessment of terrestrial carbon stock. The remote sensing component is present and has been stressed, highlighted or strengthened (revamped) throughout the paper:
  • Sections #: 3, 4, 5, 6, 7, 8 and 9 are all devoted to Geo-spatial technologies (RS and GIS) including: methods, biophysical predictors used in RS, significant RS variables, RS-GIS integrated models;
  • Section #8 is all devoted to discussing the challenging use of geo-spatial techs for carbon stock assessment in aridlands; while
  • Section #9 focuses on the gaps and limitations facing the geo-spatial technology approach for assessing above ground biomass and carbon stock.

 

• Arid Lands: Our response includes the following:

 

• The Abstract has been rewritten to highlight clearly the emphasis on arid lands (L 16 to L 28);
• The introduction section has been updated to include more materials discussing the challenges facing aridlands, and highlighting the importance of focusing and adding more research on the remote sensing of aridlands (L 41 to L 50 and (L 109 to L 117);
• Section #8 has been rewritten to address more in detail the actual status of the remote sensing studies that have been done on arid lands. Furthermore, challenges and opportunities for future work have been highlighted;
• Sections #9 and #10, are updated to show clearly the emphasis on aridlands.

 

• Statistical Analysis: Our response includes the following:

 

• Most of the sections include one or two paragraphs presenting and discussing statistical analysis: (L 150 – 160); (Figures (3, 4, 5, 7, 8 (a + b), and 9); (L 271 – 300); Figures 3 & 4; Figure 5; (L378 – L407); Figures 7, 8 and 9;
• The abundant discussion in terms of forestry is basically to highlight the importance of estimating AGB in standing forests, as this is the most accurate and easily measured quantity through RS. Hence a very critical variable for assessing terrestrial carbon stocks. However, the document was revised to omit all related redundancies or unnecessary comments on forests.  

 

• The remote sensing contributions are limited to data, sensors, and indices.

Our response includes the following:

• As indicated in the first bullet, the paper now discusses all aspects related to the use of remote sensing in assessing terrestrial carbon stock. This includes data, sensors, indices, methods (L 380 – L 407), remote sensing variables, biophysical parameters that are detectable through remote sensing and limitations especially in arid lands. This is fully covered in all sections from: Section #3 (“Geo-spatial Approach for Estimating AGB” throughout until section #9 (“Merits, Gaps, Limitations and Accuracy of the Geo-Spatial Methods”);
• Consequently, we strongly believe that our paper deserves to be published in a remote sensing journal!

 

Point 2:

• The abstract is lacking on methods.
• Keywords: sequestration – lowercase

 

Response 2:

• The abstract has been completely revised and updated. Methods appear and are highlighted in (lines: 17 – 25), in the Abstract,
• Keyword sequestration is written in lowercase (L 29)

 

Point 3:

• Authors discussed wide topics like forest biomass, carbon sequestration, policies, mapping biomass in the introduction. But I did not see relevant literature supported for the main topic ‘arid land’ carbon assessment in the introduction.
• L 75 Check with journal guidelines whether author, year citation (Eggleston et al. (2006)) or Eggleston et al. [17] citation applicable.
• L 120: Why begin with section 2, where is section 1?
• L 130: Figure 2 is the workflow, which has to move to the methods

 

Response 3:

• The introduction section has been revised to include more materials discussing the challenges facing aridlands: (L 41 to L 50) and (L 77 – L 117) and highlighting the importance of focusing and adding more research on the remote sensing of these lands,
• L 75: We checked with journal guidelines; the citation (Eggleston et al. (2006)) has been corrected to: Eggleston et al. [17]. (L 79)
• L 120: Here we refer to the subsequent sections of the MS; whereas Section 1 (which refers to the Introduction) has already been covered. This part has been rewritten to include all sections starting with section 1. (L 134 – L 143),
• L 130: As a “Review” paper, we decided not to merge the “Methods” section with the “Introduction” section. Consequently, Figure 2 appears in the Introduction section instead.

 

Point 4:

• L 167 (1934) no need the year, just reference [31]
• Table 1: why two lines for component and one line for calculation method. Can be formatted as: 3 Litter/ Debris 10-20% of Above-ground biomass [30]
• L 192-193 Remove year from references and add the reference number in parenthesis. Refer authors instruction
• L 205 (2005)
• L 213 (2006)
• L 222 (2014)
• L 229 [11-12, 19,35]
• Table 2: Are all those references related to remote sensing aspect or forestry?

 

Response 4:

• L167: This has been corrected, only the reference number appears in parenthesis, following authors instruction.
• Table 1: This has been corrected in table to read as: “10-20% of Above-ground biomass each”. Because each one of “Litters” and “Debris” has a percent of 10-20% of the AGB, NOT
• L 192-193: This has been corrected, only the reference number appears in parenthesis, following authors instruction.
• L 205: This has been corrected, only the reference number appears in parenthesis, following authors instruction.
• L 213: This has been corrected, only the reference number appears in parenthesis, following authors instruction.
• L 222: This has been corrected, only the reference number appears in parenthesis, following authors instruction.
• L 229: This has been corrected, only the reference number appears in parenthesis, following authors instruction.

Table 2: All these references are related to allometric equations that have been developed to estimate AGB of forests without the use of geo-spatial or remote sensing technologies.

 

Point 5:

• L 243 in-situ
• L 265 CS studies ‘and’ lowercase. Caption needs a sentence on what those numbers refereeing in the graph
• L 276 Do you really need a Figure to display those results? The findings can summarize using two sentences.
• L 278 Table 3 has some information which can easily find (i.e. temporal resolution, swath, cost etc.). Therefore, replacing those columns with examples of articles and major topics will be helpful.
• L 285 Hebbar [ ]
• L 287 3 years
• L 298 (1993)

 

Response 5:

• L 243 in-situ has been corrected
• L 265 was corrected in the MS. Caption of Figure 3 was edited to read: “Textual analysis of the articles (numbers) retrieved using the terms: “carbon sequestration”, “remote sensing”, and “GIS” (Google scholar accessed on 28^h March 2020 at 08:45 AM Abu Dhabi)” (L 278 and L 279)
• L 276 the figure offers a graphical representation of the results and is easier to interpret. Moreover, other reviewers ask for more figures!!
• L 278 Table 3: We believe that summarizing information about the accuracy of each sensor/data used in one table makes it easier for the reader!
• L 285 Hebbar [ ]: This has been fixed in the MS.
• L 287 3 years: This has been fixed in the MS. (L300)
• L 298 (1993): This has been fixed in the MS.

 

Point 6:

• L 359: Object-based Image Analysis
• L 388 Rosema et al. [ ]
• L 392 Morel et al.[ ]

 

 

 

 

Response 6:

• L 359: This term “Object-based” or “object-oriented” is used within the remote sensing community to indicate: RS image classification for feature extraction especially with high resolution images.
• L 388 Rosema et al. [ ]: This has been fixed in the MS.
• L 392 Morel et al. [ ]: This has been fixed in the MS.

 

Point 7:

• L 404 The Figure redrawn from one reference [97], /however it’s good to have come up a model compiling several articles.
• L 419 Ten et al. [ ]
• L 427 (2003)

 

Response 7:

• L 404: We found the figure (i. e., fig. 6) comprehensive and conveys the review message reasonably.
• L 419 Ten et al. [ ]: This has been fixed in the MS.
• L 427 (2003): This has been fixed in the MS.

 

 

Point 8:

• L 495 [55] why several
• 8 a. axis not labeled
• L 524 Missing Axis label

 

Response 8:

• L 495 [55] why several: This has been fixed in the MS.
• 8 a. axis: Labels added
• L 524: Labels added

 

Point 9:

• L 560 X axis is percentage?

 

Response 9:

• L 560: X axis is percentage

 

 

 

……………………………..

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reviewer 2 Report

General comments:

The submitted paper is an interesting review to the study of carbon assessment methods on arid environs. The research design is appropriate, the general analysis is well grounded, and the results are significant and with scientific soundness.

The structure of the manuscript is polished and well written. I would like to congratulate the authors for the wide review performed, that will be very helpful for many researches dealing with this research topic.

 

 

Structure of the manuscript

 

Abstract

I found the abstract adequate and concise.

 

Keywords

I propose changing  carbon Sequestration for carbon sequestration.

 

Introduction

Line 57: please, check this sencente: “Agreement which was signed by 197”.

Line 75: please, follow the citation format.

Line 79: “biomass, estimation”. Remove the comma.

Line 85: This sentence “much higher importance than the other types of biomass” needs a citation.

 

Section 2

Line 155: please, review this sentence.

Line 158: Table 1.

Line 166: Review this sentence.

Line 208: Check this sentence.

 

Section 3

Line 254: Check this sentence: “The estimation and modeling of carbon sequestered”.

Line 258: This sentence has been already used above: “This can be explained by the  abundance and ease of accessibility of satellite images due to the increase in RS satellites launched in the  last two decades.”

Figure 3: Please, do not use acronyms in the text of the figure.

Line 272: No Sentinel literature about this topic? It is a bit strange.

Lines 279- 301: This paragraph is too dense. Try to split it in at least two paragraphs.

Line 287: 3 years or less.

Line 297: Check citation 71.

Please, include in this section a discussion about accuracy of the reviewed methods.

 

Section 4

Lines 339-364: This paragraph is too dense. Try to split it in at least two paragraphs.

Line 338: Please, check the spaces at the end of the sentence.

 

Section 6

Line 495: Check citation 55.

Line 495: with 64-72% accuracy

Line 495: check punctuation and spaces after the citation.

 

Section 7

Line 526: please, rewrite this sentence.

Line 537: please, check this sentence.

Line 545: please, rewrite this sentence as following: “Results show that an integration of RS and spatial analysis functions in GIS can improve the overall classification result from 50.12% to 74.38%”

 

Section 8

Line 558: use of GIS tools.

Line 569: CO₂

 

Section 9

Line numbers missing after line 627.

Could you please focus this section more in the arid environments? Or at least mention it and link it somehow with the previous section.

 

Conclusions

Please, provide more conclusions about the reviews of arid regions.

Author Response

 

 

Response to Reviewer 2 Comments

 

 

Point 1:

• The submitted paper is an interesting review to the study of carbon assessment methods on arid environs. The research design is appropriate, the general analysis is well grounded, and the results are significant and with scientific soundness. The structure of the manuscript is polished and well written. I would like to congratulate the authors for the wide review performed, that will be very helpful for many researches dealing with this research topic.

 

Response 1:

• We appreciate this reviewer’s enthusiasm for our paper. We are more than happy to address all the other remarks on the structure of the MS as detailed in the subsequent points. Reviewer #2’s comments are appreciated and have improved the paper, especially regarding the grammar and syntax of many sentences. Each sentence has been carefully checked.

 

Point 2:

• I found the abstract adequate and concise. Keywords. I propose changing carbon Sequestration for carbon sequestration.

 

Response 2:

• We have changed “carbon Sequestration” into: “carbon sequestration” (L29).

 

Point 3:

• Line 57: please, check this sentence: “Agreement which was signed by 197”.
• Line 75: please, follow the citation format.
• Line 79: “biomass, estimation”. Remove the comma.
• Line 85: This sentence “much higher importance than the other types of biomass” needs a citation.

 

Response 3:

• Line 57, has been checked and corrected according to reference # [9]. (L 60 – L 61)
• Line 75, has been checked to ensure that all references follow the citation format.
• Line 79, has been checked and comma inserted between biomass and estimation has been removed.
• Line 85, The citation [Kumar L and Mutanga O 2017 Remote Sensing of Above-Ground Biomass Remote Sensing 9 935], has been added.

 

Point 4:

• Line 155: please, review this sentence.
• Line 158: Table 1.
• Line 166: Review this sentence.
• Line 208: Check this sentence.

 

Response 4:

• Line 155: the sentence: “To calculate the carbon of terrestrial ecosystems, five components must be considered, as mentioned above” has been replaced by: “Terrestrial ecosystems’ carbon is calculated considering the following five components” (L 172)
• Line 158: Table 1, row 3/column 2 and row 4/ column 2, have been changed to read: “10-20% of Above-ground biomass each” (by adding the word each at the end of the sentence)
• Line 166: the sentence is reviewed to read as: “As for SOM, it is most commonly estimated through soil sampling at various layers; SOC is then estimated using the total combustion method, as explained in Walkley and Black [39]”. (L 182 – L 183)
• Line 208: The sentence has been checked to read as: “However, these models carry the potentiality to misrepresent local, species- or community-specific variations and anomalies. Therefore, they may fail to capture variations in both forest type and the full diversity of the natural vegetation communities hence leading to an increased level of uncertainty [36].” (L 223 – L 226)

 

 

Point 5:

• Line 254: Check this sentence: “The estimation and modeling of carbon sequestered”.
• Line 258: This sentence has been already used above: “This can be explained by the abundance and ease of accessibility of satellite images due to the increase in RS satellites launched in the last two decades.”
• Figure 3: Please, do not use acronyms in the text of the figure.
• Line 272: No Sentinel literature about this topic? It is a bit strange.
• Lines 279- 301: This paragraph is too dense. Try to split it in at least two paragraphs.
• Line 287: 3 years or less.
• Line 297: Check citation 71.
• Please, include in this section a discussion about accuracy of the reviewed methods.

 

Response 5:

• Line 254: The sentence has been revised and replaced by discussion in section 7 ((L 542 – L 560)
• Line 258: The sentence has been replaced by: “Our findings confirm the increase in scientific studies incorporating RS in their methodologies for carbon sequestration estimation during the study period.” (L 271 – L 272)
• Figure 3: Acronyms were replaced by full names in the text of the figure. (L 278 and L 279)
• Line 272: We added examples using Sentinel in the MS. (L 286)
• Lines 279- 301: The paragraph was simplified and split into 2 paragraphs. (L 292 – L 323)
• Line 287: 3 years or less was corrected. (L 300)
• Line 297: Citation 71 was checked in MS.
• Table 4 includes information about the accuracy and limitations of the different RS sensors (columns 2 and 3). Furthermore, the following paragraph on the accuracy of the reviewed methods was added to section 9 (L 685 – 706), in the MS.

 

Point 6:

• Lines 339-364: This paragraph is too dense. Try to split it in at least two paragraphs.
• Line 338: Please, check the spaces at the end of the sentence.

 

Response 6:

• Lines 339-364: This paragraph was simplified and split into 3 paragraphs. (L 349 - L 377)
• Line 338: Spaces at the end of the sentence were checked in the MS.

 

Point 7:

• Line 495: Check citation 55.
• Line 495: with 64-72% accuracy
• Line 495: check punctuation and spaces after the citation.

 

Response 7:

• Line 495: Citation 55 was checked and redundancy (induced by the system) was removed.
• Line 495: with 64-72% accuracy: this was corrected in the MS.
• Line 495: Punctuation and spaces after the citation were checked and accordingly corrected in the MS.

 

Point 8:

• Line 526: please, rewrite this sentence. Line 537: please, check this sentence. Line 545: please, rewrite this sentence as following: “Results show that an integration of RS and spatial analysis functions in GIS can improve the overall classification result from 50.12% to 74.38%”

 

Response 8:

• the whole section #7 from Line 540 to Line 558 was rewritten in the MS to respond to and fix all points raised in Point 8.

 

Point 9:

• Line 558: use of GIS tools.
• Line 569: CO₂

 

Response 9:     

• Line 558: fixed and now reads: “the use of GIS tools’.
• Line 569: fixed and reads: “CO_2”

 

Point 10:

• Line numbers missing after line 627.
• Could you please focus this section (#9) more in the arid environments? Or at least mention it and link it somehow with the previous section.

 

Response 10:   

• All lines are numbered from first to last line
• More materials have been added to improve section #9 with more emphasis on arid environments.

 

Point 11:

• Please, provide more conclusions about the reviews of arid regions.

 

Response 11:

• More conclusions about the reviews of arid regions are provided in the MS. The whole Conclusion Section was rewritten!

 

 

 

 

…………………………..

 

 

 

 

 

 

Reviewer 3 Report

You can fined the comments on main review paper. 

Comments for author File: Comments.pdf

Author Response

 

 

 

Response to Reviewer 3 Comments

 

Point 1:

• General comments: The authors have done extensive review and tried to summarize sufficient literatures, in addition the authors try to includes some of the recently published papers, that could help to strengthen the review here is below:

Meshesha, T.W., Wang, J. and Melaku, N.D., 2020. Modelling spatiotemporal patterns of water quality and its impacts on aquatic ecosystem in the cold climate region of Alberta, Canada. Journal of Hydrology, p.124952.

Meshesha, T.W., Tripathi, S.K. and Khare, D., 2016. Analyses of land use and land cover change dynamics using GIS and remote sensing during 1984 and 2015 in the Beressa Watershed Northern Central Highland of Ethiopia. Modeling Earth Systems and Environment, 2(4), pp.1-12.

 

• The paper needs to be thoroughly checked for the grammar and syntax. Each sentence must be carefully checked since many of them having missing words.

 

 

 

Response 1:

• We appreciate reviewer’s # 3 reaction on the amount of effort that has been put to produce this extensive review, trying to summarize and synthesize sufficient literatures. We are more than happy to add one of the suggested literatures to the paper’s reference list namely: (Meshesha, T.W., Tripathi, S.K. and Khare, D., 2016. Analyses of land use and land cover change dynamics using GIS and remote sensing during 1984 and 2015 in the Beressa Watershed Northern Central Highland of Ethiopia. Modeling Earth Systems and Environment, 2(4), pp.1-12.). Unfortunately, the other suggested reference is out of the scope of the reviewed topic,
• Reviewer #3’s comments are esteemed and have improved the paper. Regarding the grammar and syntax of the whole MS. Each sentence has been carefully checked and missing words have been added appropriately.

 

Point 2:

• Section 1, Line 107 Comment. If you include the pros and cons of Carbon to ecosystems survival would be more interesting.
• If you include the future prediction also would be interesting.

 

Response 2:

• Line 107 Comment. We appreciate the comment about including the pros and cons of Carbon; but, we felt that adding more ecological discussion might distract from the main focus of the paper, i.e. carbon stock estimation by Geo-spatial technology.
• However, a discussion on future prediction was added to section #10.

 

Point 3:

• Section 2, Line 156 Comment. better to show some empirical equations that used to obtain SOC and carbon

 

 

Response 3:

• Line All empirical allometric equations are listed in table 2 in the MS. A paragraph about calculating SOC is also included in section 2 (L 185 - 190), It reads: “As for SOM, it is most commonly estimated through soil sampling at various layers; SOC is then estimated using the total combustion method, as explained in Walkley and Black [39]. The content of SOC included in SOM may change depending on many factors such as ecosystem, type of organic residues and land management. Many studies estimate SOC from SOM using the common factor of 1.724 (~ 58% of SOM). While this figure has been widely used in the last century, Brady & Weil, [40] concluded that it probably applied only to highly stabilized humus.”.

 

Point 4: Section 2, Line 179 Comment. better to show the equations

 

Response 4:

• All allometric equations are listed in Table 2.

 

 

Point 5:

• Section 4, Line 317 Comment. I would be more interesting on this review paper if the authors try to include how the future trend works.
• better to show the interdependence of SOC, carbon and ecosystems, and how it works with GIS and RS?
• The review paper would be more interesting if you support with more figure, since it is review.

Response 5:

• Future trend works are now discussed in detail in sections #8 and #10 of the MS.
• The interdependence of SOC, carbon and ecosystems, and how it works when using RS and GIS to estimate terrestrial carbon stock is explained and detailed in section #2, (L 176 – 196).
• We respect the reviewer’s point of view to increase the number of figures in this review. However, other reviewers are asking for less figures especially that it contains about 10 figures which is more than enough.

 

 

 

 

 

…………………………..

 

 

 

 

 

 

 

 

 

 

 

 

 

Reviewer 4 Report

This is a very long poorly organized review. The review lacks a focus and thus hard to follow. I do not recommend acceptance of this manuscript for publication on RS.

(1) The term "Carbon Assessment" title is vague. Broadly speaking there is carbon stocks and fluxes. It is not clear which one the authors mean here, nor is it clear throughout the review. The emphasis on arid lands is not justified, nor was it treated as an emphasis, but only provided with a few case studies.

(2) The Introduction is poorly written with many confusing or misleading statements. It rambles around from above ground biomass to total biomass, to carbon sequestration, to carbon stocks etc., which are all very different concepts, and I don't know which one the author is try to focus. The very first sentence of the introduction is confusing. It essentially defines "above-ground biomass" as "forest biomass". I though the authors are going to focus on above-ground biomass for this review. But I was obviously wrong and totally lost what their focus is.

(3) There are many misleading concepts or statements throughout the introduction. For example, the authors state (Line 42)"Estimation of forest carbon stocks, in  particular, is based on the estimating of terrestrial biomass." First of all, the authors seem to confuse carbon stocks (which is the total amount of carbon in forests regardless of its state of existence) with forest biomass (which refers to the dry weight to the living tree or trees in a whole forest). Second the statement is logically problematic to state that forest carbon stocks can be estimated based on terrestrial biomass because (1) carbon stocks is a broader term than biomass, (2) forest is only part of the terrestrial ecosystem. The author seem to imply (line 58) that "land use conversion to forests" as reforestation. It is reforestation only when it was forest before, otherwise it would be afforestation. The definition of "total carbon stock"  (line 74)is not accurate. The authors seem to imply (line 81) that deforestation is the primary contributor to GHGs, but it is a distant second in reality after fossil fuel. I cannot list all of such confusing/misleading statements. But these are plenty.

(4) The review on traditional methods on biomass estimation is a total distraction, and it's not connected to the rest of the manuscript as shown in figure 2. The authors only need to point out the limitations in the traditional methods that can be easily overcome with geotechnologies. The review itself for this part is poorly done. Destructive sampling and use of allometry to estimate AGB is an integral part of traditional approach to estimate AGB. There is no study that cut every tree over an area to estimate forest biomass. The destructive part only applies to samples a limited number of trees to develop the allometry for biomass estimation.

(5) Too much text was lavished on the statistics of the studies, which provide little insight on "carbon assessment" mapping. I doubt the statistics provided in figure 3 which showed on 17,000 out of 189,000 carbon sequestration studies used RS (<9%) during 2011-2020. In reality, any landscape or larger scale studies of carbon sequestration needs RS as only RS can provide wall-to-wall style measurement of the study area.

(6) The review lacks insights on the strengths and weakness of the various RS/GIS algorithms reviewed.

 

Author Response

 

 

Response to Reviewer 4 Comments

 

 

 

Point 1:

• This is a very long poorly organized review. The review lacks a focus and thus hard to follow. I do not recommend acceptance of this manuscript for publication on RS.

 

Response 1:

• The MS was completely revised. The language was double checked and improved. Many sections were synthesized and shortened. We deleted general terms like forest biomass, etc. and used more focused terms like carbon stock, AGB, etc. and analyses emphasizing both RS and Arid Lands. We pretend that the shape of the MS is now far better of what it was before your valuable remarks and inputs.

 

 

Point 2:

• The term "Carbon Assessment" title is vague. Broadly speaking there is carbon stocks and fluxes. It is not clear which one the authors mean here, nor is it clear throughout the review.
• The emphasis on arid lands is not justified, nor was it treated as an emphasis, but only provided with a few case studies.

 

Response 2:

• The term "Carbon Assessment" in the manuscript refers to Assessment of carbon stocks. This was made more explicit in the text.
• The text was revised to put more emphasis on arid lands. Text and discussion were added to the Abstract (L 16 to L 28); section #1, #8, #9 and #10.

 

 

Point 3:

• The Introduction is poorly written with many confusing or misleading statements. It rambles around from above ground biomass to total biomass, to carbon sequestration, to carbon stocks etc., which are all very different concepts, and I don't know which one the author is try to focus.
• The very first sentence of the introduction is confusing. It essentially defines "above ground biomass" as "forest biomass".
• I though the authors are going to focus on above-ground biomass for this review. But I was obviously wrong and totally lost what their focus is.

 

Response 3:

• The Introduction section was completely revised and rewritten. Since this is a comprehensive review about terrestrial carbon assessment methods using Geo-Spatial technologies, we are bound to cover diverse related and interdependent topics such as: above ground biomass, total biomass, carbon sequestration, or even carbon stocks. This lead to substantial discussion of these various topics.
• In this review our focus is on assessing terrestrial carbon stocks using geo-spatial techs. This, of course, include both veg. and soil organic carbon stocks. By measuring biomass accurately, we can retrieve the carbon amount accurately (as C is a percentage of biomass).
• AGB is the most important component of biomass and it is the only part that can be estimated through RS! This explains why the term AGB has been used frequently in the review.

 

Point 4:

• There are many misleading concepts or statements throughout the introduction. For example, the authors state (Line 42)"Estimation of forest carbon stocks, in particular, is based on the estimating of terrestrial biomass." First of all, the authors seem to confuse carbon stocks (which is the total amount of carbon in forests regardless of its state of existence) with forest biomass (which refers to the dry weight to the living tree or trees in a whole forest). Second the statement is logically problematic to state that forest carbon stocks can be estimated based on terrestrial biomass because (1) carbon stocks is a broader term than biomass, (2) forest is only part of the terrestrial ecosystem. The authors seem to imply (line 58) that "land use conversion to forests" as reforestation. It is reforestation only when it was forest before, otherwise it would be afforestation.
• The definition of "total carbon stock" (line 74) is not accurate.
• The authors seem to imply (line 81) that deforestation is the primary contributor to GHGs, but it is a distant second in reality after fossil fuel. I cannot list all of such confusing/misleading statements. But these are plenty.

 

Response 4:

• As mentioned in point 3 above, the Introduction section has been completely revised and rewritten.

Carbon stock is different from forest biomass! However, an accurate measurement of CS is only achievable if biomass amount for both: AGB and BGB, was accurately determined. CS is only retrieved as a percentage of total biomass. AGB is the most visible, dominant and dynamic part. It can also be used to predict root biomass (BGB) – see L: 172 to 183. Therefore, the review while titled to cover terrestrial CS is also covering biomass, as they are interdependent!

• The definition of “total carbon stock” which is found in: (Koala J, Sawadogo L, Savadogo P, Aynekulu E, Heiskanen J and Saïd M 2017 Allometric equations for below-ground biomass of four key woody species in West African savanna-woodlands Silva Fennica). It is also supported by the definition of (Eggleston H S, Buendia L, Miwa K, Ngara T and Tanabe K 2006 IPCC guidelines for national greenhouse gas inventories Institute for Global Environmental Strategies, Hayama, Japan 2 48–56).
• Finally, the authors totally agree with the reviewer’s opinion that burning “Fossil Fuel” is prime contributor to GHGs (L 89) while change in “Land Use” comes as second reason (including deforestation). However, burning fossil fuel issue is out of the scope of the current study.

 

Point 5:

• The review on traditional methods on biomass estimation is a total distraction, and it's not connected to the rest of the manuscript as shown in figure 2. The authors only need to point out the limitations in the traditional methods that can be easily overcome with geotechnologies. The review itself for this part is poorly done.
• Destructive sampling and use of allometry to estimate AGB is an integral part of traditional approach to estimate AGB. There is no study that cut every tree over an area to estimate forest biomass. The destructive part only applies to samples a limited number of trees to develop the allometry for biomass estimation.

 

 

Response 5:

• The review section on traditional methods in biomass estimation was intended to point out the limitations in these methods that can be easily overcome with geo-technologies in one side; and to complete the story of biomass and carbon stock estimations on the other. However, the main objective of the MS was focused on the use of Geo-spatial technologies rather on the traditional methods. The illustration in figure 2 was made purposely to reflect this! The section on traditional methods is now rewritten and improved to reflect this point clearly on the revised MS.
• We totally agree that destructive sampling and use of allometry to estimate AGB is an integral part of traditional approach to estimate AGB. It is absolutely right to say “there is no study that cut every tree over an area to estimate forest biomass. The destructive part only applies to samples a limited number of trees to develop the allometry for biomass estimation”. Some confusion may have been caused by the authors that frustrated Reviewer #4; we apologize for this! Reviewer #4 is kindly invited to re-read the MS in its actual status (L 203 – L 211 and (L 744 – L745) to ensure that we meet the required standards and that we are all speaking the same language!

 

 

Point 6:

• Too much text was lavished on the statistics of the studies, which provide little insight on "carbon assessment" mapping. I doubt the statistics provided in figure 3 which showed on 17,000 out of 189,000 carbon sequestration studies used RS (<9%) during 2011-2020. In reality, any landscape or larger scale studies of carbon sequestration needs RS as only RS can provide wall-to-wall style measurement of the study area.

 

Response 6:

• We revised all the statistics conducted in the review by adding more insights on “carbon assessment” mapping. Figure 3 was double-checked again against data retrieved by accessing Google Scholar on 28th March 2020, concerning the period: 2011-2020. We confirm retrieving almost the same percentage of < 9%; when using the following keywords:
  • Term: “Carbon Sequestration” = 204,000
  • Term: “Carbon Sequestration AND Remote Sensing” = 17, 900

 

Point 7:

• The review lacks insights on the strengths and weakness of the various RS/GIS algorithms reviewed.

 

Response 7:

• The “strength and weakness” of the RS/GIS methods are discussed in section #4 (RS-based methods) (L 380 – L 407), and in section #9 (Merits, Gaps and Limitations of the Geo-Spatial Approach). Additionally, a complete paragraph discussing the different methods and algorithms is added to section # 9 (L685 – 706). Furthermore, table 4 includes information about the accuracy and limitations of the different RS sensors (columns 2 and 3). Furthermore, the following paragraph on the accuracy of the reviewed methods was added to section #9 (L 685 – 706), in the MS.

 

 

 

………………………………

 

 

Round 2

Reviewer 1 Report

L 100 geo-spatial technologies (RS and GIS)

L 110 delete i.e., RS and GIS

L 131 If you introduced “geo-spatial technologies” to supplement RS and GIS use it throughout.

L 136: gives

L 134-143: No need to give numbers 1-9 since section number is already covered the aspect

L 170: What is the symbol before section (§ section 2.1), check this throughout

Cite references in the main text in numerical order.

Table 3: Check Table Formatting i.e. two lines in the header raw and a line in the bottom raw

Table 3 column heading: Spatial Resolution (m) – then delete meters from each raw

Heading Swath (km) delete unit from each column

L 332 RS and GIS replace with geo-spatial technologies

Figure 8a poor quality. Make axis line black line with tick marks. Remove vertical gridlines.

L 737: to improve

Author Response

Comments and Suggestions for Authors

 

L 100 geo-spatial technologies (RS and GIS)

L100:  ”geo-spatial technologies” is now replacing (RS and GIS) throughout the MS

 

L 110 delete i.e., RS and GIS

”geo-spatial technologies” is now replacing (RS and GIS) throughout the MS

 

L 131 If you introduced “geo-spatial technologies” to supplement RS and GIS use it throughout.

”geo-spatial technologies” is now replacing (RS and GIS) throughout the MS

 

L 136: gives

L 136 now starts with: “Sections 3 - 4: give an overview...”

 

L 134-143: No need to give numbers 1-9 since section number is already covered the aspect

The lines numbers are now removed

 

L 170: What is the symbol before section (§ section 2.1), check this throughout

The symbol was removed

 

Cite references in the main text in numerical order.                                          

All references in the main text have been checked and are in numerical order

 

Table 3: Check Table Formatting i.e. two lines in the header raw and a line in the bottom raw

Table 3: has been checked and formatted to add two lines in the header and a line in the bottom raw.

 

Table 3 column heading: Spatial Resolution (m) – then delete meters from each raw

Table 3 has been re-edited so that column heading: is now written as “ Spatial Resolution (m) “ AND the word “meter” was deleted from each raw accordingly

 

Heading Swath (km) delete unit from each column

Table 3 has been re-edited so that column heading is now written as “Heading Swath (km)“ AND unit from each column was deleted accordingly

 

L 332 RS and GIS replace with geo-spatial technologies

L332: RS and GIS is replaced with “geo-spatial technologies”

 

Figure 8a poor quality. Make axis line black line with tick marks. Remove vertical gridlines.

The resolution of Figure 8-a has been increased to be 300 dpi. Black axis lines with tick marks have been added. The vertical grid lines have been removed.

 

L 737: to improve

Line 337-338: the line has been rewritten to read as: “to improve soil and plant productivity, to increase food security, and to control land degradation”