Using Airborne LiDAR to Map Red Alder in the Sappho Long-Term Ecosystem Productivity Study
Round 1
Reviewer 1 Report
1.In the research, can you display and analyze the laser point cloud morphology of a single tree in detail? Such as, for example, the difference between red alder (Alnus rubra) and other dominant tree species point cloud data.
2.In the paper, can you give a more in-depth introduction to the theoretical methods and characteristics you have adopted.
3.In the paper, you mainly study the classification model, localization and mapping of Red Alder, It would be great if you can discuss further improvements to meet other tree species.
Author Response
Please see attachment. Thank you!
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript used ALS to map red alder in Sappho and get very accurate result. The overall content meets the publication standards. However, there are also major issues that make me to reconsider. First concern is the figures. The figures are not well organized. Some of them are not even cited in the main text and needs to be improved. Detailed comments are below. The second concern is that Fig. 6 and Fig.7 are the main results and not analyzed in the body text.
Fig. 1, 2, 3, and 4 are not cited in main text.
Fig. 1 add a, b, c and scale in subfigures. Top right figure will be better showing the state boundary, city name, etc.
Fig. 2 what is the purpose to add 6 decimals in the DBH value? Do you have a such accuracy?
Fig. 3 It seems combination of Fig.2 and Fig. 3 is also possible since there is not so much information in the figure.
Fig. 5 set the y-axe size to smaller and let them fit in one page.
Fig. 6 and Fig. 7 are your main results. Only two sentences?
Author Response
Please see the attachment. Thank you!
Author Response File: Author Response.docx
Reviewer 3 Report
The material presented in the manuscript is interesting, well written, easy to read. However, without trying to minimize the amount of work that went into its development in my view it represents more of a report than a research article. The main limitations have to do with the relatively small study area, the very limited number of training/validation samples and that no effort was made to extend the model from the study area to a larger area with perhaps natural forest cover to make a case for model replicability, which would have only needed a modest ground validation effort. In addition, important technical details were left out of different sections of the manuscript (see specific comments below).
L36, “everything that can be seen from an aerial point-of-view.” – Is this accurate and correct? ,is it only limited to a specific part of the visible spectrum?
L38-39, should probably repharse to “commonly in use emit hundreds of thousands of pulses per second, and a few are capable of or than a million”.
L66-86, This introduction would benefit from adding the work presented in https://www.mdpi.com/1424-8220/22/1/35 A Comparison of Three Airborne Laser Scanner Types for Species Identification of Individual Trees
L70 “They reported 21, 39, 18, five, and 10 cases that classified two, 70 three, four, five, and six species respectively”, this is not clear.
L134-136, my general experience is that accuracies are typically better than 30 cm horizontal and 15 cm vertical
Section 2.1, what is the surface area of the study area?
L200-215, how were distance and azimuth measured? What tools, methods?
L218-225, surveyed how, tools, methods, referred to what coordinate system?
L227, are the horizontal and vertical accuracies for these datasets reported somewhere?
L241, “the aggregate pulse density was 17.26 points/m2” this is ambiguous … are you talking pulses or returns(points), if pulses how were the #pulses identified?
L244 – 299 It will be particularly useful for other researchers trying to understand tree location uncertainties if you could quantify the positional errors of the survey as whole (overall RMSE) and for individual trees (such as a boxplot+ wiskers), this can also be expanded on section 3.1 (Results)
L261, Didn’t the plot survey technicians also collect GNSS data to verify the locations of the plot corners and consecutively the tree positions in the lidar data? Also, could the process have been automated such as taking the centers and then automatically adjusted to minimize the distance between the legend and the center of each tree circle? Wouldn’t an automated process be more reliable?
L340, why 99th percentile, vs. max height? What is the average difference between these metrics for your tree populations??
L381 & L383 how does this sample size 644 and 70% training 30% compare to other studies??
Section 2.6 Red Alder Classification Model. This section can benefit by including a flow/process diagram.
Author Response
Please see the attachment. Thank you!
Author Response File: Author Response.docx
