Advancements in Monitoring Tree Phenology Under Global Change: A Comprehensive Review
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The review article entitled “Advancements in Monitoring Tree Phenology under Global 2 Change: A Comprehensive Review” aims to provide a comprehensive overview of the advancements in monitoring tree phenology in the context of global change. It highlights the limitations of traditional ground-based methods and discusses the integration of modern technologies like remote sensing, digital cameras, and sensor networks, including the role of citizen science. The paper identifies challenges posed by global change and data integration, explores applications of phenological data in various fields, and concludes by outlining future directions emphasizing interdisciplinary collaboration and standardized methodologies.
General concept comments
The review topic is highly relevant given the accelerating impacts of climate change on ecosystems structure and functionality. It appears to cover the key areas of advancement in phenology monitoring techniques, from traditional to modern. The gap in knowledge identified is the need for more comprehensive, spatially and temporally extensive, and integrated phenological data to understand and predict ecological responses to global change. The references cited seems appropriate for establishing the context and the challenges in the field.
I found the paper to be overall well-written and well-organized. Furthermore, this is a timely topic and of considerable interest to researchers and forest practitioners alike.
Specific comments
Lines 85-86. The authors can also refer to the part VI of the ICP Forests manual (http://icp-forests.net/page/icp-forests-manual). A programme launched in 1985 under the Convention on Long-range Transboundary Air Pollution (Air Convention, formerly CLRTAP) of the United Nations Economic Commission for Europe (UNECE) aiming at a comprehensive compilation of information on the condition of forests in Europe and beyond
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
I find the general topic of the manuscript entitled 'Advancements in Monitoring Tree Phenology under Global
Change: A Comprehensive Review' of interest for a publication in MDPI Forests. The manuscript reports a review of last advancements in the monitoring of tree phenology.
I found the introduction appropriate and the manuscript well structured. All the main issues related to the monitoring of tree phenology are presented. My main concern is related to the 'comprehensive' adjective, included in the title. From the point of view of the variety of topics covered, the review can be considered comprehensive. Neverhteless, some of the specific topics can undoubtedly be further detailed. Although the main focus of the paper is to present an overview of new advancements, a few words can also be spent on established and less recent approaches, which can provide a term of comparison with newer ones. I suggest to include a few relevant publications which are missing in the manuscript, which are provided hereafter.
The manuscript is well written from the standpoint of the English.
I have specific comments and suggestions in order to improve manuscript readability:
Lines 50-51: Climate change conditions are in some cases anticipating the senescence, due to reduced water availability and prolonged droughts events that are increasing under climate change scenarios. I suggest to also consider this.
Line 110: Is this a specific reference to Copernicus Sentinel-2 satellite constellation, or is a general consideration on Sentinel satellites (including medium spatial resolution e.g. Sentinel-3)?
Limes 113-115: Dealing with UAV, I would stress the revisit frequency issue and coverage capacity. How feasible is acquiring large surfaces with high revisit frequency? I suggest to stress also limitations about the use of UAV for phenology monitoring.
Lines 129-130: I suggest to avoid this sentence in the figure caption, since it is also present in the main text.
Line 131: I suggest to include at the beginning of section 2.2.2 a sentence to also introduce metric estimation approaches that does not necessarily use machine learning approaches. Two relevant publications are: i) https://doi.org/10.1016/j.agrformet.2016.01.006, which describe a variety of processing techniques to extract phenology from digital images of vegetation; ii) https://doi.org/10.3390/rs14030721, which describe an automated, generalized and transferable procedure to exploit full satellite Earth observation time series to extract plant phenology metrics.
Lines 205 and 233: Satellite Earth observation monitoring can provide near-real-time information, not real-time, due to the time needed to trasfer and process the data. I suggest to modify the terms accordingly.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
