LiDAR as a Tool for Assessing Timber Assortments: A Systematic Literature Review

Round 1

Reviewer 1 Report (Previous Reviewer 4)

A review of the utilization of lidar from terrestrial, airborne, and space-based platforms for characterizing timber attributes is presented in this study. While an important topic, extensive editing and revisions are still needed to clarify content and integrate additional information. Corrections to grammar are needed throughout and all are not listed here. Under Introduction, much content is briefly stated without a clear description. For instance, in the third paragraph, (starting with the word “differently”) additional content is needed. Items in parentheses after “classification of logs” should be integrated as complete sentences, since this information is relevant. Instead of using “i.e.” to briefly list items in parentheses, integrate information as complete sentences within the paragraph to provide the reader with a clearer picture. Moreover, as a review, such information should be better described in-text rather than briefly stated. There are grammatical errors throughout the text that need to be corrected and language should be improved in each section. Some specific examples are listed below, but this is not comprehensive. There are many errors in information presented (e.g. ICESat-2 operated until 2021?), and substantially grammatical corrections needed. Even before moving on to Section 2, Section 1 requires substantial editing and revisions to warrant further consideration for publication. The significance of the review is unclear. 

Abstract

Line 14: remote “the”, to change to “depict forest structure”

Line 15: “despite that the literature..”

Line 16: widely explored

Line 17: What is timber assortments estimation? As indicated in the previous round of revisions, I think that there is a need to define what encompasses timber assortments, and this should be done early on. Is there a complete lack on knowledge on the topic or are some aspects addressed in the literature? This is a strong statement without first defining what are timber assortments.

Line 20: what is meant by securitized? Suggested change to “examined”?

Line 23: here, “few studies” with timber assortments are indicated, but in Line 16, “a lack of knowledge” was highlighted, thus unclear.

Line 30: where does spaceborne lidar stand, in comparison?

Introduction

Grammatical corrections are needed throughout.

Line 35:  “..and improving human welfare”

Line 38: providing

Line 38: aboveground biomass

Line 39: What is meant by assessment of timber products? Further describe how this is achieved through destructive approaches.

Line 43: are collected

Line 44: what is “elaborated”?

Line 52: This sentence is very long; break into multiple sentences. For instance, a new sentence could start after “georeferenced point clouds”.

Line 54: Table 1

Line 55: A full stop is missing before “In”

Line 59: How does accurate measurement of trees equate to carbon stock, listed in parentheses?

Line 62: This paragraph is quite brief. More specific examples on the application of lidar can be included. More importantly, given the different lidar platforms and corresponding spatial scales, more specific information should be added when listing the applications such as land cover classification.

Line 67: What about UAS? (Coops et al. 2021) Present separate from airborne lidar.

Coops, N.C., Tompalski, P., Goodbody, T.R.H., Queinnec, M., Luther, J.E., Bolton, D.K., White, J.C., Wulder, M.A., van Lier, O.R., & Hermosilla, T. (2021). Modelling lidar-derived estimates of forest attributes over space and time: A review of approaches and future trends. Remote Sensing of Environment, 260, 112477

Line 72: ICESat

Line 74: ICESat-2 is still in operation. Clearly, more work is needed on a review of the literature, to present accurate information.

Line 71-75: Describe relevant applications with each satellite lidar and present airborne lidar as a separate paragraph.

Line 98: Low expensive?

Line 104: Versatility and applicability versus lidar sensors mounted on other platforms needs to be well established before this paragraph.

Line 147: Should LAI be listed with the lidar systems here?

Author Response

We are very grateful to this reviewer for highlighting the importance of this study's topic. We made our best to improve the quality of our manuscript. The points of concern raised by him/her have been addressed in the updated version of the manuscript, which we feel has been improved considerably. More precisely, we rephrased, changed, and integrated pertinent information in many sections, particularly in the introduction and mythological approach sections. We sent the manuscript to the MDPI editing service for language revision. Please, you can find attached a point-by-point replication to explain how we modified the text following the comments received.

Author Response File: Author Response.docx

Reviewer 2 Report (Previous Reviewer 2)

Language and organization The authors apparently have not had a native English editor look at this revision.  I outline problems in the first 300 lines. Time prevented any more.  Simple grammatical errors were so numerous that listing them consumed much of my reviewing time.

The title states a limited objective but the paper ranges over nearly every conceivable topic of LiDAR measurements in forests .

Overall

1.       Methodology a single search engine and limited to 2000-2021.  A complete review should include other search engines.  Also a search of the citations within the retrieved articles can reveal original publications that may more accurately reflect the original work.

2.       Key word assortments is often called merchandizing in American publications.  May have missed relevant American publications.

3.       The paper is an overly comprehensive review of a limited search.

Line 16 is wider explored - more widely explored

Line 23-25 three singular vs plural errors in this one sentence. 

Line 27-30 run -on sentence

Line 46 spacing problem  1  or 2 paragraphs?

Line 50 no period

Line 50 stating the obvious  of course harvesting is the most accurate measurement.

Line 55  no period

Line 62 one sentence paragraph-  can be included in next

Line 71 , 76, 78 , 85 no period

Lin 79 also play

Line 82 was  by who, where , and when,   suggest has been or can be

Line 85 the handle to handling

Line 89-93 run on suggest 2 or 3 separate sentences.

Line 93 but ? should it be by

Line 95 is increased  to has increased.

Line 96 well description of trees    improper adverb

Line 98 low expense  not expensive

 

Lines 82-101 this paragraph consists of one or two disconnected sentences on each subject with little coordination.  Was very hard to read.

 

Lines 102 – 106   Whole paragraph is one sentence.

Line 114 Itd-based studies 

Line 124 – word spacing is strange may need to separate URL   descriptions are a mix of descriptions, tradenames and acronyms .

Line 126-130 another single sentence paragraph.

Line 145  Table 1 seems out of place  I would think it is a result or conclusion.

Line 154 papers were  scrutinized and analyzed  How?  Figure 1 implies simple sorting

Line 176 table 2  I would suggest third column be listed as source rather than study , also a and b are in very small font very hard to read.

Line 182 distribution of studies retrieved by the literature review.

Line 184  carry out research not papers

Line 187 represents studies without a system within…

Line 221 and thereafter allowed implies permission-   retrieved or resulted in is more appropriate.

Line 222 extrapolated is incorrect

Line 230  needs to be two sentences  general terms were more frequently used and timber assortment was infrequently studied. Poorly implies improper methods.

Line 233 indicating lack of ….

Line 234 Concerning….

Table 5 Caption is unclear did you  retrieve 304 papers and some were repeated in two categories. Or were duplicates papers retrieved in the search  Needs to be clear in caption as well as text.  There is no reference to the table in the section that explains the numbers

Table 5 should be redone to indicate which categories had the duplications The number of duplicates is larger than any category  how do we know which differences are real.  

 

 Number of collected papers should be spelled out

Line 238  assortment and morphology the least ?

Line 244 Figure 8 text discusses continents but map is by country  large number of countries in Europe mask  the larger number of papers.

Author Response

We apologize for the lack of clarity. However, we are very grateful to this reviewer for having provided constructive and valuable comments to improve the quality of the manuscript. The points of concern raised by him/her have been addressed in the present version of the manuscript, which we feel has been improved considerably. The benefited of the MDPI services for language correction in order to make the text clear and easier to read. Moreover, we changed the title of our study, as suggested. The new title is “LiDAR as a tool for assessing timber assortments. A systematic literature review”.

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

The article is an extensive study on the 3 basic problems of the use of LIDAR in forestry in the last 20 years. The state of the art is an innovative approach to the study of literature. A scientific study is very detailed. The authors collected, analyzed and classified over 100 literature items. They presented methodological data for them in interesting tables and graphics. The study may be a good source of knowledge for other studies in forestry.

The study procedure is clear and justified. The study data are rightly chosen and sufficient. The Authors of the article correctly described the study; it is important that the study procedure can be reproduced by other researchers.

Overall, the article is complete, only needs to be revised: moderate English changes required. The English site of the article should be improved because some sentences are long and overcomplex.

Author Response

We are very grateful to this reviewer for having highlighted the importance of this study. We made our best to improve the readability and comprehensibility of our manuscript. The points of concern raised by him/her have been addressed in the present version of the manuscript, which we feel has been improved considerably. A native English speaker from journal editing services reviewed the manuscript.

Round 2

Reviewer 2 Report (Previous Reviewer 2)

This paper has been vastly improved since my last review. The English and organization has been improved.  The section from line 338-462 still has some wording and sentence length problems.  I would suggest further work on this section to bring the English style and grammar to the level of the rest of the paper. .  

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

 

The article has a relevant theoretical contribution to the LIDAR theme. Only suggest increase some citations os forest, climate and lidar. I think that is important contribute and innovate in this theme.

Reviewer 2 Report

I see very little in this paper to merit publication.  The main trust seemed to be LiDAR to measure merchantable tree components, which is listed as assortment and provisioning in different parts of the manuscript.  Sentence structure and grammar are uneven from tolerable to nearly incomprehensible.  I did not think some of the classifications made much sense and some, like including plantation in conifer, deciduous , mixed   are just plain wrong.   Most of the discussion seemed as if single lines from the abstracts of cited papers are combined into a chronology.   The first use of UAV LiDAR was not in 2017 but in the late 1990's.  

I believe  a simple bibliography indexed by useful categories may be the best way to present the work done here.

Highlighted are examples of poor English used in several sections of the manuscript.   

Comments for author File: Comments.pdf

Reviewer 3 Report

Comment

This manuscript is a review paper focused on challenges and opportunities for timber assortments evaluation through LiDAR. The topic is suitable for remote sensing fields. However, the style of this manuscript is similar to research article because it contains Materials and Methods, Results, and Discussion chapters. Since this is a review paper, that style is not suitable. I suggest that authors might consider to reorganize whole context and to point out some special items as chapter title. I also recommend that authors could refer review papers in this journal.

My main concern is that a large amount of papers have addressed this topic concerning timber estimation based on LiDAR. I could not fully understand that the special or novelty of the references cited in this manuscript (in your Materials and Methods). Since the Remote Sensing is an international journal, some of scientific sound are necessary. Therefore, I suggested that special and novelty of the references should have more descriptions in their contributions in this study filed. It might let audiences clearly know the contribution of your paper. Overall, I suggest that authors might consider to reorganize whole context before publication.

Reviewer 4 Report

A review of the utilization of lidar for characterizing timber attributes is presented in this study. While an important topic, extensive revisions are needed to clarify content and integrate additional information. Extensive corrections to grammar are needed throughout and all are not listed here. It is strongly recommended to review and correct grammatical errors. While some challenges and opportunities are highlighted, there are places where content needs to be integrated, corrected, and more clearly communicated. There is missing information in some parts, and given that this is a review, is necessary. At the very beginning of the paper, relevant information estimated using lidar data need to be highlighted, as well as a clear discussion of each sensor platform and what is typically estimated from each. It is important to highlight the different level of detail possible with the lidar sensor, as this impacts accuracy of the forest parameter being estimated. Among current limitations of the work, at a minimum, the review should be structured and revised to: (1) define what encompasses timber assortments, (2) discuss each lidar platform, lidar-based missions (in the case of satellite) and capabilities of each, and (3) describe methods employed for analysis. Section 1.2. dives into lidar technology without consideration of the lidar system. For instance, reconstructing trees from space-based lidar may not be feasible, yet there is no way to determine what lidar technology is being discussed without going to the data source cited. The Introduction is insufficient and lacking information to build a clear picture of the focus of the review. Restructure content to group and present under key themes apparent from the literature review. The scale of the study, such as local, regional, national, or international scale should also be made clear throughout.

Line 12: Several factors impact the capability to accurately depict tree-level architecture, including sensor platform. For instance, this statement may not apply to spaceborne lidar.

Line 14: forestry applications

Line 15: Change “poor” to “little”

Line 15: What is timber assortments assessments? Are these specific variables or timber attributes that could be stated here? This term may not be familiar to audiences worldwide, thus clarification is needed to communicate that is meant by timber assortments.

Line 18: Why were 304 papers selected? How many were there?

Line 27: Revise this sentence to communicate the key challenge of each data source mentioned here.

Line 30: Revise: huge lidar data? What is meant by model lidar data? Do authors mean model timber attributes with lidar data?

Line 36-40: What aspects of SFM?

Line 41: what about unmanned aerial systems (UAS)? Is UAS grouped with and aircraft-based instruments?

Line 43: How does satellite lidar facilitate monitoring? Do the sensors offer repeat coverage? Add relevant citations.

Line 51: Stand level or plot level?

Line 58: accuracies in tree measurements

Line 73: Biodiversity-related forest aspects indicated; what are the other aspects? Strongly suggest first providing background on the topic, that is, the information being reported, then transition to discussion of lidar as a tool for potentially deriving this information.

Line 76: What is considered “large-scale” monitoring? How is DA integrated ITD?

Line 95: applications

Section 1.2: Unclear. What lidar system is discussed? One would not expect individual trees to be constructed using photons from ICESat-2, for instance. Specify the lidar technology being discussed.

2. Materials and Methods: Add a descriptive paragraph before Figure 1. A reminder of the objective of the study is also needed (or even emphasize the purpose of the literature review). Table 3 is unclear; what do the IDs mean? Lidar device or system?

Line 220: Which was mounted on..

The ICESat mission ended in 2010. Isn’t there any work on ICESat-2?

Figure 5. Revise to include what each cluster represents in the legend, instead od only the letters. Why are percentages in parentheses?

Line 274: What does “While till that moment” mean?

Line 419: RF is also a non-parametric method.