An Automated Hemispherical Scanner for Monitoring the Leaf Area Index of Forest Canopies
Round 1
Reviewer 1 Report (Previous Reviewer 1)
The article is excellent
Once you read the results it becomes confuse to which experiment it corresponds and if you return to the methodology section you get even more confused. I recommend that at the end of the methodology section you can add a Table indicating each experiment, indicating the experimental place and some comments. It will be clearer for the reader.
These are some changes that should be done to make the article better.
It will be clearer if an image of a tree is added with each of the vertical and horizontal directions (lines 137-139 also lines 177-182).
In lines 241-242, it is missing in which months the experiment took place.
In Figure 4b, which are the units of radiation intensity. Was it measured with a piranometer?
In figure 5, the x-axis should only be radiation intensity plus unit.
In figure 6 eliminate estimation in both axes.
In the discussion section, lines 398-405 talk about the effect of sunny days during scanning. How does LAI measurements with the LAI-2000 Plant Canopy Analyzer cope with this problem?
A paragraph in the discussion section should add data processing of the information. Is the data processed within the microcontroller in field, or the values saved in a memory and analyzed in a computer afterwards? Which is the time required to obtain the result?
English editing
The sentence (line 61-63) is too long. It should finish after camera and LEDS.
In line 371, the sentence in meaningful. “The design of the AHS was elaborately studied”
Author Response
Dear Editors,
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “An Automated Hemispherical Scanner for Monitoring Leaf Area Index of Forest Canopies” (ID: 1859190). Those comments were all valuable and very helpful for revising and improving our paper, as well as the guiding the interpretations of the results from our study. We have studied the comments carefully and have made corrections, which we hope meet with your approval. Below, please find our point-by-point responses to the comments of the reviewers and the revisions made.
Response to Reviewer 1 Comments
Point 1: Once you read the results it becomes confuse to which experiment it corresponds and if you return to the methodology section you get even more confused. I recommend that at the end of the methodology section you can add a Table indicating each experiment, indicating the experimental place and some comments. It will be clearer for the reader.
Response 1: Accepted and revised.
Thank you for your rigorous nice suggestion. According to your opinions, I have added a table of experimental methods and comments.
Table 2. Experiment descriptions
|
The experiments |
The experimental places |
Comments |
|
Influence of the spatial heterogeneity of radiation on PAI estimation |
Northeast Forestry University's Urban Forestry Demonstration Research Base |
Investigation of observation conditions |
|
Influence of radiation intensity on estimations of PAI |
Northeast Forestry University's Urban Forestry Demonstration Research Base |
Investigation of observation conditions |
|
Comparison with the LAI-2200 plant canopy analyzer |
Northeast Forestry University's Urban Forestry Demonstration Research Base |
Accuracy verification |
|
Field experiment |
Maoershan Experimental Forest Farm |
Monitoring the Leaf Area Index of Forest Canopies |
Point 2: It will be clearer if an image of a tree is added with each of the vertical and horizontal directions (lines 137-139 also lines 177-182).
Response 2: Experiment descriptions
We completely understand the reviewer’s concern.According to your opinion, we added two directions in the image
Figure 1. AHS design drawing and physical drawing: (a) The diagram of the AHS with all components labeled; (b) Schematic of obtaining data from multiple directions, the horizontal and vertical arrows indicate the direction of rotation of the servo motors; (c) A photos of the AHS in the field test.
Point 3: In lines 241-242, it is missing in which months the experiment took place.
Response 3: Thanks for your correction. Time of experiment has been described in 2.4.2 Data collection.
Point 4: In Figure 4b, which are the units of radiation intensity. Was it measured with a piranometer?
Response 4: We gratefully thank you for the precious time the reviewer spent making constructive remarks.
To calculate light penetration through the canopy based on Beer’s law, foliage is treated as a black body. Our instrument use an optical low-pass filter , therefore, the measured value has no unit.
Point 5: In figure 5, the x-axis should only be radiation intensity plus unit.
Response 5: Thank you so much for your careful check.
As the previous question, our instrument has no unit.of measured value.
Point 6: In figure 6 eliminate estimation in both axes.
Response 6: Accepted and revised.
Thank you for your rigorous consideration and your comments.
Point 7: In the discussion section, lines 398-405 talk about the effect of sunny days during scanning. How does LAI measurements with the LAI-2000 Plant Canopy Analyzer cope with this problem?
Response 7: Thank you for your rigorous comment.
LAI-2000 will be difficult to make reasonable measurements during sunny days, unless readings aremade in early morning orlate evening.
Point 8: A paragraph in the discussion section should add data processing of the information. Is the data processed within the microcontroller in field, or the values saved in a memory and analyzed in a computer afterwards? Which is the time required to obtain the result?
Response 8: We gratefully appreciate for your valuable suggestion.
The data are stored in the SD card in a txt file labeled with the time (i.e., MMDDHHMM.txt). and calculation were automatically completed by programming in MATLAB
Point 9: The sentence (line 61-63) is too long. It should finish after camera and LEDS.
Response 9: Accepted and revised.
Point 10: In line 371, the sentence in meaningful. “The design of the AHS was elaborately studied”
Response 10: Accepted and revised.
The Manuscript was organized as Forests guidelines (The Main body of MS is followed by sections headed Abstract-Introduction- Materials and Methods-Results-Discussion-Conclusions-References). Also, we used Editage (www.editage.cn) to edit our paper. We believe that the language is acceptable for potential publication.
We are appreciating for your carefulness. We tried our best to improve the manuscript and made some changes, corrected errors, and added some comments in the manuscript. These changes will not influence the content and framework of the paper. Once again, we appreciate for Editors/Reviewers’ warm work earnestly, and hope that the corrections will meet with approval.
Yours sincerely,
Yibo Wen1, LL Zhuang2, Hezhi Wang3, TX Hu3, Wenyi Fan3,*
1 College of Forestry, Shenyang Agricultural University, Shenyang, China; [email protected]
2 School of environmental science and engineering, Shandong University, Shandong, China; [email protected]
3 Academy of Inventory and Planning, National Forestry and Grassland Administration
4 School of Forestry, Northeast forestry university, Harbin, China; [email protected]
* Correspondence: [email protected]; School of Forestry, Northeast Forestry University, Harbin 150040, China. Email: [email protected], telephone number: +86-0451-8219-1341 W.-F. Fan
Reviewer 2 Report (Previous Reviewer 2)
This study proposes a new method for rapid PAI measurement and the preliminary results are scientifically sound. There are some suggestions to improve the quality of the article as below:
L56-58: DHP is a relatively cheap method, so the cost is not its limitation. Need to address the need for a new method more carefully.
L84: PAI first appears here but without a full name (abstract doesn't count).
L78-81: I believe your system is a passive optical system, so why do you mention LiDAR here? There are some gaps in the logic flow.
L113-118: Is PAI the same as effective LAI in your study? In your later paragraphs, PAI is used most of the time, so make sure the use of terminology is consistent.
Figure5: The caption says the y-axis should be effective PAI, but the label is PAI instead.
Discussion: Some paragraphs repeat what was described in the result section. The discussion should focus more on significance, uncertainty, limitation, and future work.
L420-421: This is true only if the woody materials stop growing during a year, or the variation in WAI is negligible.
Author Response
Dear Editors,
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “An Automated Hemispherical Scanner for Monitoring Leaf Area Index of Forest Canopies” (ID: 1859190). Those comments were all valuable and very helpful for revising and improving our paper, as well as the guiding the interpretations of the results from our study. We have studied the comments carefully and have made corrections, which we hope meet with your approval. Below, please find our point-by-point responses to the comments of the reviewers and the revisions made.
Response to Reviewer 2 Comments
Point 1: L56-58: DHP is a relatively cheap method, so the cost is not its limitation. Need to address the need for a new method more carefully.
Response 1: Accepted and revised.
Thank you so much for your careful check., We removed the ”quite costly and” description.
Point 2: L84: PAI first appears here but without a full name (abstract doesn't count)?
Response 2: Accepted and revised.
Thank you for your rigorous nice suggestion.The full name has been added.
Point 3: L78-81: I believe your system is a passive optical system, so why do you mention LiDAR here? There are some gaps in the logic flow.
Response 3: Accepted and revised.
We completely understand the reviewer’s concern. We added a transition description” The passive optical system is a fixed sensor”.
.
Point 4: Is PAI the same as effective LAI in your study? In your later paragraphs, PAI is used most of the time, so make sure the use of terminology is consistent.
Response 4: Accepted and revised.
Thank you for your rigorous nice suggestion. I revised the terminology in the later paragraphs
Point 5: Figure5: The caption says the y-axis should be effective PAI, but the label is PAI instead.
Response 5: Accepted and revised.
Thank you so much for your careful check. Figure 5 has been modified.
Point 6: Discussion: Some paragraphs repeat what was described in the result section. The discussion should focus more on significance, uncertainty, limitation, and future work.
Response 6: Accepted and revised.
Point 7: This is true only if the woody materials stop growing during a year, or the variation in WAI is negligible
Response 7: Accepted and revised.
The Manuscript was organized as Forests guidelines (The Main body of MS is followed by sections headed Abstract-Introduction- Materials and Methods-Results-Discussion-Conclusions-References). Also, we used Editage (www.editage.cn) to edit our paper. We believe that the language is acceptable for potential publication.
We are appreciating for your carefulness. We tried our best to improve the manuscript and made some changes, corrected errors, and added some comments in the manuscript. These changes will not influence the content and framework of the paper. Once again, we appreciate for Editors/Reviewers’ warm work earnestly, and hope that the corrections will meet with approval.
Yours sincerely,
Yibo Wen1, LL Zhuang2, Hezhi Wang3, TX Hu3, Wenyi Fan3,*
1 College of Forestry, Shenyang Agricultural University, Shenyang, China; [email protected]
2 School of environmental science and engineering, Shandong University, Shandong, China; [email protected]
3 Academy of Inventory and Planning, National Forestry and Grassland Administration
4 School of Forestry, Northeast forestry university, Harbin, China; [email protected]
* Correspondence: [email protected]; School of Forestry, Northeast Forestry University, Harbin 150040, China. Email: [email protected], telephone number: +86-0451-8219-1341 W.-F. Fan
Author Response File: 
Author Response.pdf
Reviewer 3 Report (Previous Reviewer 3)
The revised manuscript is improved – thanks to the authors for considering my comments. There are still some issues with regards to loose/incorrect use of terminology which would benefit from minor revision.
1. According to Equation 4, you derive PAI (e.g. corrected for clumping). But throughout the manuscript, both ‘PAI’ and ‘PAIe‘ are used. It’s not clear whether you’ve applied the clumping correction or not. If no clumping correction was applied, please consistently refer to your estimates as ‘PAIe‘ (or if it was applied, please consistently use ‘PAI’).
2. On L85-86, when discussing your study, you state that ‘PAI values are converted to the LAI, which is obtained using long-term observation data by subtracting the wood area index (the leaf-off state) (WAI)’. You never actually carry out this conversion, so this seems misleading and should be deleted. N.B. the discussion on this point (417-421) is fine and should be kept.
3. On L113-118, two different concepts appear to be mixed up (or at least it's not written clearly). ‘Effective’ means that clumping isn’t accounted for, whereas ‘LAI’, ‘WAI’, and ‘PAI‘ refer to whether leaves, woody material, or all material is considered. It would be great to make this as clear as possible, to avoid any confusion and prevent the propagation of incorrect terminology in the literature.
4. Related to this point, if you haven’t applied the clumping correction, please use ‘WAIe‘ as opposed to ‘WAI’.
5. Finally, I don’t follow the text about understory vegetation (L422-429). Since the AHS is at 1.2 m, how high is the vegetation understory?
Minor language suggestions:
L139: ‘sensor, can’ -> ‘sensor, which can’
L409: ‘significant’ -> ‘substantial’
L475: ‘, which has a full 360-degree azimuth range, should’ -> ‘a full 360-degree azimuth range should’
Author Response
Dear Editors,
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “An Automated Hemispherical Scanner for Monitoring Leaf Area Index of Forest Canopies” (ID: 1859190). Those comments were all valuable and very helpful for revising and improving our paper, as well as the guiding the interpretations of the results from our study. We have studied the comments carefully and have made corrections, which we hope meet with your approval. Below, please find our point-by-point responses to the comments of the reviewers and the revisions made.
Response to Reviewer 3 Comments
Point 1: According to Equation 4, you derive PAI (e.g. corrected for clumping). But throughout the manuscript, both ‘PAI’ and ‘PAIe‘ are used. It’s not clear whether you’ve applied the clumping correction or not. If no clumping correction was applied, please consistently refer to your estimates as ‘PAIe‘ (or if it was applied, please consistently use ‘PAI’).
Response 1: Thank you for your comments and unified adjustment
Point 2: On L85-86, when discussing your study, you state that ‘PAI values are converted to the LAI, which is obtained using long-term observation data by subtracting the wood area index (the leaf-off state) (WAI)’. You never actually carry out this conversion, so this seems misleading and should be deleted. N.B. the discussion on this point (417-421) is fine and should be kept.
Response 2: We gratefully thank you for the precious time the reviewer spent making constructive remarks.‘PAI values are converted to the LAI, which is obtained using long-term observation data by subtracting the wood area index (the leaf-off state) (WAI)’ is a transition statement for the later paragraphs..
Point 3: On L113-118, two different concepts appear to be mixed up (or at least it's not written clearly). ‘Effective’ means that clumping isn’t accounted for, whereas ‘LAI’, ‘WAI’, and ‘PAI‘ refer to whether leaves, woody material, or all material is considered. It would be great to make this as clear as possible, to avoid any confusion and prevent the propagation of incorrect terminology in the literature.
Response 3: Thank you so much for your careful check. Accepted and revised.
These are two important concepts, which we have revised.
Point 4: Related to this point, if you haven’t applied the clumping correction, please use ‘WAIe‘ as opposed to ‘WAI’.
Response 4: Thank you for your comments and unified adjustment
Point 5: Finally, I don’t follow the text about understory vegetation (L422-429). Since the AHS is at 1.2 m, how high is the vegetation understory?
Response 5: Thank you so much for your careful check.
A small part of the vegetation understory shrub is over 2m.
Point 6: L139: ‘sensor, can’ -> ‘sensor, which can’
Response 6: Accepted and revised.
Point 7: L409: ‘significant’ -> ‘substantial’
Response 7: Accepted and revised.
Point 8: L475: ‘, which has a full 360-degree azimuth range, should’ -> ‘a full 360-degree azimuth range should’
Response 8: Accepted and revised.
The Manuscript was organized as Forests guidelines (The Main body of MS is followed by sections headed Abstract-Introduction- Materials and Methods-Results-Discussion-Conclusions-References). Also, we used Editage (www.editage.cn) to edit our paper. We believe that the language is acceptable for potential publication.
We are appreciating for your carefulness. We tried our best to improve the manuscript and made some changes, corrected errors, and added some comments in the manuscript. These changes will not influence the content and framework of the paper. Once again, we appreciate for Editors/Reviewers’ warm work earnestly, and hope that the corrections will meet with approval.
Yours sincerely,
Yibo Wen1, LL Zhuang2, Hezhi Wang3, TX Hu3, Wenyi Fan3,*
1 College of Forestry, Shenyang Agricultural University, Shenyang, China; [email protected]
2 School of environmental science and engineering, Shandong University, Shandong, China; [email protected]
3 Academy of Inventory and Planning, National Forestry and Grassland Administration
4 School of Forestry, Northeast forestry university, Harbin, China; [email protected]
* Correspondence: [email protected]; School of Forestry, Northeast Forestry University, Harbin 150040, China. Email: [email protected], telephone number: +86-0451-8219-1341 W.-F. Fan
Author Response File: Author Response.pdf
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 is very interesting and shows innovation tips for further and cheaper LAI measurements.
However, someone that would like to replicate your work will find it very difficult. I would like to make the following comments on sections 2.2 and 2.3.
- The operation of the servomotors in line 118 is not clear. As well their properties, type, accuracy (stepper motors, dc, pulsed motors) are not considered. As the servomotors get more precise their cost and interface make them expensive.
- How are the servomotors programmed to cover the entire hemisphere?
- In the left image of Fig 1., there is a horizontal and a vertical arrow that tries to indicate the movement but it’s difficult to understand. The figure at the right seems to have a lens that is not explained in the text.
- In lines 141-45 of section 2.3 it is explained that a 7x 7 matrix will be the information from the sensing. How much time it takes? Each section of the matrix corresponds to a georeferenced value, that are measured as the motors move. Is there any noise in the data caused by the motors?
I would recommend to make it easier for any reader, to add a block diagram of the embedded system and explain it. It should also have a programming block diagram so that we can understand the motors synchronization? They move first all horizontally? Or the move horizontally and vertically?
Please correct in line 195 the precipitation unit to mm. Also correct title 2.4.3 to data processing.
In Figure 2 (line 233) the third graph includes an equation with 2 points.
It is not clear if line 250 talking about radiation intensities corresponds to Fig. 4.
If you have LAI in figure 4 and corresponds to unstable light intensities in sept 2014. Which would be the graph for May 1st.
Considering that figure 6 is correlated against each plot mentioned in Table 1, which is the effect of plant density. In each graph of Figure 6 there is no mention against plot number. For example, plot 1 has two varieties different from plots 2 and 3. What does for SQ values mean in each graph. Why is LAIe at day 120 so different in the 3 plots? Can you add images that help to explain your ideas? What was the measurement with the LAI-2200 equipment?
Sunbeam direction is not considered in the article. How can there be a discussion with Fig 3c that does not exist (lines 340-343).
Comments for author File: Comments.pdf
Reviewer 2 Report
This study presents a novel approach for automatic LAI measurements in the field, and the method is scientifically sound. However, the structure of the article needs some improvement to increase its readability. In addition, some typos were identified so English proofreading is necessary. Below are some specific suggestions:
L74-75: When AHS appears in the article for the first time, probably also describes which category of LAI instrument it belongs to (e.g. upward-looking instrument based on gap fraction theory.
L94-95: I suggest integrating Eq 1 and 2 into Eq 3 to demonstrate G(theta) is not needed.
L115-116: I guess the temperature and humidity are not used for calibrating the instrument, so probably make it clear. The description here looks confusing.
L128: with what wavelength? The living foliage have relatively high transmittance and reflectance above 490 nm, so the wavelength is important.
2.2: I don't see the scattering radiation from foliage under direct Sunlight was taken into consideration. Does the instrument limit the measurement time during dawn and twilight? I know you assess the effect of scattering error in 2.3.2, but it's worth mentioning how the instrument is designed to prevent this error or did you do the scattering correction for the above measurement? You probably need to justify why you don't need to consider it. In addition, does the instrument have only one sensor which rotates constantly to measure the light from different directions? You don't mention how many zenith and azimuth directions it measures, and what are the angles.
2.4.2: Sky condition? Wasn't the LAI-2200 used in the same data collection campaigns, or was LAI-2200 only used for lab experiments?
L217: Split the equation out of the sentence. It doesn't read well.
3.1.1: The calibration should be done between the above and below instruments, but all the calibrations were done against No1. Why?
Figure 3: (a) I suggest adding the LAI from LAI-2200 here for easier comparison. (b) Isn't the y-axis of b "radiation intensity"? Also, there is no (c) subplot but the caption shows there is a (c)
3.1.3: This should be put prior to 3.1.2, as the measured LAI in 3.1.2 was clearly affected by the intensity.
3.1.4: The relationship is clearly not 1:1, though they are based on the same gap fraction theory. I suggest adding it into discussion.
3.1: I feel 3.1.2 - 3.1.4 could be integrated into one section.
L289-290: Specify what the principles are. How are those principles implemented by the instrument design?
Figure 6: The labels show they are all LAI for SQ. What are the arrows? Should mention in the caption.
L308: The randomly distributed foliage is seldom satisfied in the real situation, so probably worth mention what's the uncertainty caused by this factor.
L321-327: It's worth mentioning how the instrument is designed to follow the two principles.
L328-334: This is more result rather than discussion.
L335-352: This could be combined with L321-327. Again, how the instrument is designed to avoid this condition automatically?
Discussion: Another issue I can think about is dust. The dust accumulated on the instrument could potentially affect the measurements. How to address this issue?
Discussion: It needs a restructured. The paragraphs feel like jumping around without a strong cohesion.
Conclusion: Add some quantitative results here.
Reviewer 3 Report
The submitted manuscript describes a new system for automated and continuous measurement of effective plant area index (PAIe). Due to the high cost and logistical constraints of manual field measurements, there is a clear need for such systems to improve temporal characterisation of vegetation dynamics. The manuscript is generally well-written and easy to follow, and I believe the results would be of interest to the readership of Forests. In addition to my comments below, the manuscript would benefit from some minor language editing to catch typos and spelling errors.
Main concerns
1. The Introduction misses a lot of recent literature, and the authors need to better set their study in the context of relevant work. Examples include automated digital hemispherical photography (https://doi.org/10.1016/j.agrformet.2020.107944 , https://doi.org/10.1016/j.ecolind.2021.107549, laser scanning (https://doi.org/10.3390/s140814994), transmittance-based sensors like LAINet (https://doi.org/10.1016/j.compag.2014.08.003), PASTIS-57 (https://doi.org/10.3390/rs10071032), the use of PAR sensors (https://doi.org/10.1016/j.agrformet.2017.09.004), and low-cost camera traps (https://doi.org/10.1016/j.agrformet.2021.108516).
2. The authors use the term LAIe, but since woody material is incorporated, they are really measuring effective plant area index (PAIe). I think it would be better to use the term PAIe throughout the manuscript to avoid confusion. Alternatively, if the authors wish to keep using LAIe, they could subtract their leaf-off (i.e. WAIe) values from the time-series – this would be simple to do. Currently, they mention this as a possibility in the Discussion, but don’t actually apply it as part of their method.
3. Since observations are available at multiple azimuth angles, clumping could be accounted for using the logarithm averaging method (https://doi.org/10.1016/0168-1923(86)90033-X), which would allow the authors to go from PAIe to PAI (or LAIe to LAI). I think it’s at least worth mentioning as a possibility in the Discussion, since it would improve the utility of the authors’ system.
4. The selection criteria used to define ‘valid data’ need to be properly described. Were particular thresholds (e.g. of transmittance values) adopted?
5. I feel the Discussion is a bit repetitive and light touch. A more in-depth Discussion on the implications of the Results (rather than just repeating the Results themselves) would strengthen the manuscript.
Specific comments
1. Introduction
L38: This definition is for ‘green LAI’, whereas the standard definition of LAI includes all leaf material (whether yellow, green, or brown).
L58-68: See my main concern 1 – a lot of relevant literature is missed here which should be discussed to give the reader a clear idea of the current state of the art.
L60: The digital camera methods typically don’t measure ‘reflectance’ per se, so I think it would be better to say ‘spectral properties’.
L70-73: I think this point is overstated, since it has been shown that the use of RAW images and data screening can overcome these issues (https://doi.org/10.1016/j.agrformet.2014.05.014, https://doi.org/10.1016/j.agrformet.2020.107944). It is worth noting that transmittance-based methods also have their own problems (e.g. need for calibration of above and below sensors, artefacts caused by variable illumination, especially if the above sensor is not close to the below one – https://doi.org/10.1016/j.agrformet.2018.02.003, https://doi.org/10.1016/j.compag.2014.08.003).
L79: ‘LAI-2000’ should be ‘LAI-2200’?
2. Materials and Methods
L96-101: See my main concern 2.
L100: Missing references here?
L126: I think ‘the wavelength range’ should be ‘the visible wavelength range’?
L135-137: See my previous comment – I think this point is a bit overstated given advances in RAW data processing and screening.
L146: How long does a complete scan take? Could there be errors caused by wind moving the branches during a scan (e.g. https://doi.org/10.1016/j.rse.2015.06.014)?
L153-155: How often is calibration needed? I guess the above sensor may degrade at a faster rate than the below one (which has less UV exposure due to shading of the canopy)? It would be useful to mention as a practical consideration for deploying your method.
L164: It would be good to clarify you mean spatial heterogeneity of the light environment here. As written, it could be confused for spatial heterogeneity of the forest itself.
L184-185: Please give the common names of all species with the Latin names in parentheses (seems like a mixture of both at the moment).
L206-210: How far away was the above sensor from each forest plot?
L216-217: Actually the LAI-2000 and LAI-2200 sensor extends only to 74.6 degrees (see the instrument manual for further info). Did you reweight the rings so that they summed to 1?
3. Results
L242: It would be best to avoid using ‘significantly’ here (and throughout the rest of manuscript) unless you have tested for statistical significance, as it could be misleading to the reader – ‘substantially’ or similar would be more appropriate.
L258-259: There is no Figure 3c?
L267-269: What does this mean in practice? Using a threshold (e.g. DN > 50)?
Figure 5: It would be good to add the 1:1 line so we can see if the AHS is biased with respect to the LAI-2200. It looks like the AHS is slightly underestimating low (< 3) values and slightly overestimating high (> 5) values – this should be discussed.
L289-290: See my previous comment – what are the specific selection criteria for valid data?
4. Discussion
L308: ‘obtaining LAI values through optical methods requires diffuse sky condition and randomly distributed foliage’ – this is a bit of a sweeping statement – not all optical methods require diffuse skies (e.g. ceptometers can work in direct sun), and non-randomly distributed foliage is mostly an issue if you are assuming LAI = LAIe. It is less of a problem for measuring LAIe itself, or if clumping is corrected for.
L312: Some relevant references for methods to validate global LAI products with continuous measurements could be given here (e.g. https://doi.org/10.1016/j.agrformet.2016.11.267, https://doi.org/10.1109/JSTARS.2020.3040080).
L326-327: See previous comment on thresholds – what is a moderate irradiance condition? It would be useful to quantify.
L341-352: This section is all about Figure 3c, which doesn’t exist in the submitted manuscript – please delete or add the missing Figure 3c.
L365: Rather than WAI, your leaf-off values are actually effective WAI (WAIe), since woody material is also subject to non-random distribution, i.e. clumping.
L370-371: How high is the understory vegetation? > 1.2 m?
L383-384: Previous work has shown the 57 degree method to be more robust than Miller’s theorem (https://doi.org/10.1016/j.agrformet.2014.03.016), so saying ‘the condition is more limited’ is not necessarily true.
L385-386: Actually, there are similar scanning systems using active LiDAR (https://doi.org/10.3390/s140814994). Perhaps yours is the first using a passive optical sensor. It would be good to clarify this in the text.
L389: See my previous comments on this.
L392-393: This isn’t really true - a fisheye lens has a full 180 degree zenith and 360 degree azimuth range, so surely your scanning system (which only extends to zenith of 70 degrees) is more limited in terms of angular observations?
L403: Previous work has found a number of drawbacks to the oblique digital repeat photography approach (e.g. https://doi.org/10.1890/13-0652.1, https://doi.org/10.5194/bg-12-5995-2015, https://doi.org/10.1016/j.agrformet.2017.08.012, https://doi.org/10.1016/j.agrformet.2020.107944), so I would argue your approach has advantages over these methods (rather than the other way around).
