Estimation and Simulation of Forest Carbon Stock in Northeast China Forestry Based on Future Climate Change and LUCC
Round 1
Reviewer 1 Report
General comments
The topic of this manuscript is of high impact and falls fully within the scope of the Journal and the title clearly reflects its contents. The introduction is very effective in contextualizing the study and defining its objectives, even though it is mainly focused on the Chinese case and lacks some more references to the international context. In the Materials and Method section, the study area and data acquisition and pre-processing are well presented, while the following text should be reorganized, and its readability improved. For this purpose, I suggest adding a flowchart that includes all the processing steps in a more schematic way. The description of methods is in fact too dense and confusing, and methods are mixed with results and sometimes with discussion. For example, the results of the PLUS model validation (table 2) and prediction (table 3 and table 4) should be moved to the results section. In addition, table 3 and 4 will be more effective by adding some simple indexes to facilitate the comparison among the different estimates. Results should be revised, mainly by avoiding mixing content related to methods, results, and discussion. In this section, some figures (fig 5 and 9) are hardly understandable: they should be better explained in the text or replaced by simpler graphs. Moreover, at least a raw assessment of the uncertainty of the FCS estimation should be added. The discussion section should be reshaped and widened by including pieces of discussion reported in the previous sections.
Specific comments
Page 2 Line 47: the sentence “they weaken the spatial heterogeneity” is not clear, I suggest adding “due to” between “weaken” and “the spatial”
Page 2 Line 84: I suggest writing “above ground biomass” instead of “above ground biological”
Page 4 Line 123, Figure 2: change “aspest2” with “aspect”
Page 4 Line 132: replace “precision” with “resolution”.
Page 4 Line 147: “data accuracy” should be replaced with “data resolution”. As above (page 4, line 132), “resolution” is the appropriate word to describe the cell size of a gridded dataset. Accuracy (closeness to the ground truth) and precision (a measure of statistical variability) are in fact mainly related to the main statistical features of data.
Page 5 Line 156, Table 1: I suggest adding borders among categories, to improve the readability
Page 7 Table 3: I suggest specifying that this table refers to some sort of calibration, to guide in the choice between MC and linear regression, while table 4 present the simulated land use areas applied in the FCS estimation.
Page 8 Line 229: “decreased” should be replaced with “is expected to decrease” or “would decrease”. I think the use of a past tense for predicting future scenarios is inappropriate (the same is suggested for other sentences which discuss future predictions in the remainder of the manuscript)
Page 8 Line 246: some more details should be added to describe how the soil data have been refined
Page 8 Line 252: the meaning of « depression » associated with forests is unclear (the same applies at Page 16 Line 390)
Page 13 Line 317, table 6: these figures should be relative numbers (with a minus or plus sign), otherwise it is not clear whether the changes are positive (an increase) or negative (a decrease)
Page 16 Line 390: check the word “depression” as highlighted above (page 8 Line 252)
Page 17 Line 464: change citation format of « Peng et al., 2018 » with a number between square brackets
Page 21 Line 655: this reference number [52] is not cited in the text
Page 22 Line 661: this reference is incomplete and duplicated: the last references (52-56) should be renumbered and citations in the text need to be checked
Author Response
Dear reviewers,
Thank you very much for your constructive comments. Your comments have played a key role in further improving the quality of this manuscript. We attach great importance to your comments, have made careful revisions, and responded to your suggestions one by one. Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is well prepared and presents an effective methodology and exploratory analysis for estimating and simulating forest carbon stock in Northeast China Forestry based on future climate change and LUCC. Results reveal how important the availability of data is for the assessed context, and indicates ways for developing a national-scale effort for monitoring carbon stocks. For me, it is an excellent initiative and is on the way to being published. Therefore, I would like to present some adjustments that can help to improve the study:
- Introduction
Structured to state the main topics related to the research. The current form shows Figure 1 within the Introduction, but it is referenced only in Line 114. Please, take care to send this figure to the subsection “2.1.1 Study Area”.
Lines 107-122: Edaphoclimatic conditions are relevant for the purpose of the study’s investigation. Please, insert a reference to enable readers to validate the information about the study area.
2.1.2 Data Acquisition and Preprocessing
Lines 129-132: “The land use data is a multi-period set from 1980 to 2020 constructed by manual visual interpretation using Landsat remote sensing images as the main information source. The dataset covers 6 major categories and 25 subcategories, and the data precision is 30m.” This data is authorial or from a reference? If it is from a reference, cite it. Table 1 shows the website, but it is essential to mention it throughout the text.
2.2 Methods
In this section, the method is explained; however, some information can be added to highlight its capability. The total of samples used to perform the analysis, and the selected method to avoid undersampling or oversampling, for example. In this sense, please, explain if the total of points was defined based on a specific method or was random. There are various methods for sample pixels collection, and this is a step that impacts results. Also, the description of the size of the assessed area and the use or not of good practices for sampling (Olofsson et al., 2014*) will help to verify if oversampling or undersampling happened.
* Olofsson, P., Foody, G. M., Herold, M., Stehman, S. V., Woodcock, C. E., & Wulder, M. A. (2014). Good practices for estimating area and assessing accuracy of land change. Remote sensing of Environment, 148, 42-57.
2.2.1 Patch-generation land use change simulation (PLUS) model
Line 179-182: Kappa. The authors used Kappa for accuracy assessment. It can be more helpful to focus on the disagreement and wonder how to explain the error, rather than focus on the agreement and worry that randomness might explain some of the correctness, which is what the Kappa indices of agreement do. There are papers attesting the unsuitability of Kappa to this kind of assessment, for example. Therefore, I would like to recommend you read the following papers and consider other alternatives, to avoid critics and reach more robustness.
Akinyemi, F. O., Pontius Jr, R. G., & Braimoh, A. K. (2017). Land change dynamics: Insights from Intensity Analysis applied to an African emerging city. Journal of Spatial Science. https://doi.org/10.1080/14498596.2016.1196624.
Foody, G. M. (2020). Explaining the unsuitability of the kappa coefficient in the assessment and comparison of the accuracy of thematic maps obtained by image classification. https://doi.org/10.1016/j.rse.2019.111630.
Pontius Jr, R. G. (2019). Component intensities to relate difference by category with difference overall. International Journal of Applied Earth Observation and Geoinformation. https://doi.org/10.1016/j.jag.2018.07.024.
Pontius Jr, R. G., & Millones, M. (2011). Death to Kappa: Birth of quantity disagreement and allocation disagreement for accuracy assessment. International Journal of Remote Sensing. https://doi.org/10.1080/01431161.2011.552923.
A starting point to improve the methodological part regarding accuracy is to follow the recommendations provided in this paper:
Olofsson, P., Foody, G. M., Herold, M., Stehman, S. V., Woodcock, C. E., & Wulder, M. A. (2014). Good practices for estimating area and assessing accuracy of land change. Remote Sensing of Environment. https://doi.org/10.1016/j.rse.2014.02.015.
If you decide to maintain Kappa as an accuracy measure, justify it with solid arguments. As it stands in the text, seems that was chosen by default.
Line 201: Table 3, Figure 4, and the text between Lines 214-224 seem like results. Therefore, it can be placed within the Results section.
Results: well structured. Based on the interesting Results, the Discussion section can be improved to expand the range of analysis. The current one is too general. The potential of citation will be benefitted from a discussion of the proper results in a remote sensing-based subsection before the current ones.
In the subsection on limitations, the Authors can cite potential strategies to overcome the presented adversities, and the potential and capability of the method to separate classes traditionally confused and, definitely, monitor carbon stocks. Do the increase in temporal resolution able to solve confusion with similar classes? Also, what input features can be benefitted from the increasing valid number of observations?
Edaphoclimatic and crop management practices may be important conditioning factors for carbon stock differences and, consequently, the monitoring of the phenomena. For territorial planning purposes, there are variations of forest management practices on a seasonal scale in the study area?
Writing
Line 186: Please, correct a typo (add space) in “0.8(Table 2)”.
Line 237: Please, correct a typo (spaces) in “categories(km2 )”. Also, add a final point.
Please, add a final point after each Figure and Table caption.
Line 349: Please, correct a typo (add space) in “Greater-Khingan-Mountains>Lesser”.
Author Response
Dear reviewers,
Thank you very much for your constructive comments. Your comments have played a key role in further improving the quality of this manuscript. We attach great importance to your comments, have made careful revisions, and responded to your suggestions one by one. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
see attached file
Comments for author File: Comments.pdf
Author Response
Dear reviewers,
Thank you very much for your constructive comments. Your comments have played a key role in further improving the quality of this manuscript. We attach great importance to your comments, have made careful revisions, and responded to your suggestions one by one. Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been improved and most suggestions have been incorporated. In particular, the flow chart in figure 3 is very effective and helpful and table 6,7 9 and 10 increase the text readability very much. However, there are still some points that should be improved. The main weakeness is related to the addition of FoM analysis, for both method and results description (see specific comments). Furthermore, despite methods, results and discussion are now better organized, some contents should still be moved from one section to another. Discussion should be more focused on the study results.
Specific comments
Page 2 Line 84: I suggest writing “above ground biomass” instead of “above ground biological”
Page 4 Lines 134-136: I suggest using “density” or “canopy cover” instead of “denseness”. The same should be done throughout the text.
Page 5 Line 158, Table 1: the border under the first line should be completed
Page 7 Line 200: I suggest using “density” or “canopy cover” instead of “denseness”.
Page 7 Lines 221-248: it is still a mixture between Method and Results. The methods adopted for model validation are K coefficient and FoM: their description is part of methods; on the contrary, accuracy results obtained are correctly reported in this results section.
Page 7 Lines 235-237: theoretically, this index ranges from 0% (in case B is equal to 0) to 1 (when A, C and D are equal to 0, i.e. in case no errors are detected). This is clearly explained in the reference Pontius et al. 2008, already cited by the authors as [38]:
“The figure of merit can range from 0%, meaning no overlap between observed and predicted change, to 100%, meaning perfect overlap between observed and predicted change”….” the amount of correctly predicted change is larger than the sum of the various types of error, figure of merit is greater than 50%”
Page 5 Line 247: I am sorry, but I think an FoM value equal to 0.174 means that the overlap between observed and predicted change is very small, therefore it cannot be considered a good result.
Page 8 Line 262: add borders among Current, MC (2010-2020), MC(2030-2050) and Linear regression
Page 9 Lines 273-283: this part concerns the discussion
Page 10 Lines 286-293: this part concerns the discussion
Page 10 Lines 294-297: these details concern the method
Page 10 Line 300: Figure 5 should be better explained in the text or at least in the caption: what is the meaning of the left and right semicircles, respectively?
Page 10 Line 298 (Table 5): add borders among scenarios
Page 15, Table 8: again, some borders could make clearer this table. I suggest adding borders between the two times considered
Page 16 Line 360: the use of the past tense (“was”) is not appropriate for future scenarios.
Page 16 Line 362: in addition to figure 10, tables 9 and 10 should be mentioned. Figure 10 should be better explained in the text or at least in the caption: what is the meaning of the left semicircle? Is the land use distribution in 2020?
Page 16 Lines 366-373: this part concerns discussion
Page 18 Line 423: I suggest changing the first sentence with: "The main limitations of this study are related to the accuracy of the data and the model"
Page 18 Line 424: I suggest using “density” or “canopy cover” instead of “denseness”.
Page 18 Line 427: I suggest to replace “The other” with “Another critical point is”
Page 19 Line 445: check “depression”
Page 20 Line 519: The acronym NR should be spelled out
Page 18 Line 424: use density (or canopy cover) instead of denseness
Page 18 Lines 410-418 – check the verb tenses: the use of a past tense doesn't seem appropriate for presenting future scenarios
Author Response
Thank you for your further optimization comments. We attach great importance to it and have made careful revisions. Please refer to the attachment for details.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The manuscript has been significantly improved. The authors carefully took into account all remarks from reviewers, and made changes or additions accordingly. For example, they introduced Figure of merit (FoM) to estimate the accuracy of the simulation results.
The paper is a good illustration of the use of process-based models to estimate forest carbon stocks and their expected trends. The comparison of the results obtained from different models still remain to be considered in future research.
Author Response
Thank you for your constructive and correct comments on this article during this period of time, which have significantly improved the quality of our research and have given me a lot of inspiration for future research. Thanks again for your sincere thanks!
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.
