Crown Structure Explains the Discrepancy in Leaf Phenology Metrics Derived from Ground- and UAV-Based Observations in a Japanese Cool Temperate Deciduous Forest

Round 1

Reviewer 1 Report

The manuscript presents an interesting attempt to assess the potential of UAV in order to track the crown leaf phenology. To achieve this, the authors used the measurements of 43 tree species located in 1.5 ha permanent plot from a cool temperate forest within Mt. Sobatsubu, Japan. Also, they used DJI Phantom 4 observation in order to construct ortophoto as well as to derive specific vegetation indices that later were used in the assessment of the crown leaf phenology. From the beginning of the manuscript, I find the topic interesting, easy to read and kindly new - trying to make use of UAV based observation to deep the crown leaf phenology.

The introduction section provides the background of the study and it is well documented.

Materials and methods sections are presented clearly enough and statistical analysis are used appropriately. I suggest you to add a figure with the entire workflow of the methodology, it will be much easier for the reader to follow the entire manuscript. The results are presented in an appropriate form. In the discussion section, in comparison with their results, the authors present similarities with other studies.

The conclusion section of the manuscript needs to be improved. I suggest the authors not to include references in this section, all these parts should be moved to discussion section. The conclusions should be briefly stated based on the results of the study.

Some specific comments are given below:

L185 : I would replace the term “researcher”. May be an appropriate term would be “specialist”.

L206-207: Sufficiently overlapping?? Please avoid using this kind of explanations. Which is the optimal overlapping? Please give more details.

L385: Figure 2.  I would suggest introduce the regressions equation directly in the figure and remove it from the it’s caption.

L454 : “… correspond well.. ”,  avoid use this kind of expressions. Please give more details.

L509 : “ The researchers…” Please avoid using this term “researchers” May be more appropriate could be authors.

L591-592 : “Therefore….. “ this should be moved to the conclusion sections.

L595-617: Entire section should be reviewed and shorten (according to comments specified above).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Budianti et al. investigated the UAV's performance in determining key phenological dates related to leaf expansion and leaf falling in a deciduous forest in Japan. The UAV-based results were compared with ground-based observation. The hierarchical Bayesian modeling was also applied to detect the sources of uncertainties involved in the UAV approach. The manuscript is well-developed, providing comprehensive reasoning, analysis, and Discussion.

One point may be included in Discussion, that is, the accuracy of the UAV approach still depended on the frequency of running the UAV, which is similar to human-based observation. Thus, the UAV method may be useful for large-area surveys regarding spatial heterogeneity, rather than on-site observations over time like the “phenocam”.

Other places can be improved:

Line 274-278, it is still unclear how the dates were determined. What is the Zhang’s method?

Line 275, add “over time, respectively,” before “representing…”

Line 277, how were the thresholds of “5%” and “95%” chosen?

Line 300, use “CLC” directly since the brief has been introduced earlier.

Line 600, change “should be stated” to “is noticeable”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf