Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study 15 analysed erosion gullies across four typical regions of Northeast China. Overall, The topic is interesting, and the manuscript is well organized. Some minor revisions are recommended before publishing.

1. "Development Characteristics and" can be discarded in the title, and some phraseologies can be revised accordingly.
2. Some  paragraphs are too long, can be condesed greatly, and be divided into several shortp aragraphs (Lines 47-84, 216-258, 307-340 et al.).
3. Plotting scale and direction indicator are recommended in Fig. 4 and Fig. 6.
4. Fig. 5 is not needed. 

Author Response

"Please see the attachment."

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, this manuscript titled “Research on the Development Characteristics and Influencing Factors of Erosion Gullies in the Northeast Black Soil Region” presents a well-structured and empirically grounded study that addresses a critical ecological and agricultural issue in Northeast China’s black soil ecosystem. The integration of long-term remote sensing data and in-situ field surveys provides a robust methodological foundation for exploring gully erosion dynamics, making the work both scientifically rigorous and practically relevant. Using 10-year high-resolution Google Earth imagery (2011–2021) and 2021 field survey data, this study systematically analyzed the spatio-temporal evolution characteristics of erosion gullies and contains some interesting findings and are valuable for the understanding of gully erosion mechanisms in the unique black soil ecosystem of Northeast China. Specifically, it fills the research gap in comprehensive environmental thresholds of erosion gullies in this region, clarifies the differentiated driving factors of gully development across semi-humid and semi-arid zones, and offers actionable scientific support for soil and water conservation and gully erosion control in major grain-producing areas. If the author is willing to address the following issues, this manuscript is suitable for publication on Land.

 Specific Revision Suggestions

There are spelling errors throughout the manuscript (e.g., “Glass land” should be “Grassland” “Baizhan” should be “Baiquan”). It is recommended to conduct a comprehensive proofread for grammatical and spelling inaccuracies, and standardize the use of abbreviations (e.g., the full name of “RTK” should be specified upon first occurrence).

References are incomplete: relevant studies published in 2024–2025 (e.g., Xiao et al., 2025; Ni et al., 2025) have not been included. It is suggested to supplement the latest literature to reflect the cutting-edge nature of the research.

In the Methods section (Line 103), it is not stated whether the resolutions of the images from 2011, 2016, and 2021 are consistent. If inconsistent, please add a step for resolution normalization processing.

Line 171: The selection criteria for gully erosion samples (e.g., M1, G1) (e.g., whether they cover different slopes and land use types) should be supplemented.

Line 162: For the interpretation of Google Earth images, accuracy assessment results (e.g., Kappa coefficient, confusion matrix) are not provided. It is suggested to supplement the interpretation accuracy data for each region and each land use type to enhance data reliability.

Lines 164–170: RTK technology was used for field verification, but the positioning accuracy of RTK (e.g., horizontal error, vertical error) is not specified. Please supplement this information to facilitate readers' understanding.

Lines 187–203: Is the interpretation workload of "9376 gully erosion features" sufficient to cover the four regions? It is recommended to supplement the statistical basis for the sample size (e.g., sampling error < 5%).

Line 174: Time of field verification (e.g., May 2021, October 2021) and its consistency with the image acquisition time are not stated. To avoid verification biases caused by differences in vegetation coverage, please supplement this information.

Lines 216–258: Although the authors have elaborated on the results in detail, the content is somewhat lengthy. It is suggested that the authors further streamline these results to help readers quickly grasp key information.

In Figure 10 (Line 351), the fitting equations illustrate certain phenomena, but statistical parameters should be provided or included in the supplementary tables, as this information is fundamental.

Line 385: It is recommended that the authors focus on the scale issue in this part of the discussion—whether the observed phenomena are universal when scaling up from the small watershed scale to larger scales. The lack of this content reduces the depth of the manuscript.

Relevant references should be supplemented in the discussion section, such as Lines 445–448, 386–394, 404–407, and 418–427.

It is suggested that the authors reduce the overall length of the manuscript, focusing on the Results and Discussion sections. Although the manuscript addresses certain issues and presents interesting findings, the expression should be refined.

Overall, based on this manuscript, I recommend considering publication after revisions.

Comments on the Quality of English Language

The authors should check grammar of all sentences to ensure its readiability.

Author Response

"Please see the attachment."

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors address an important and timely research problem: the environmental conditions and thresholds governing the development, stabilization, and initiation of gully erosion in the black soil region of Northeast China. The manuscript presents a substantial body of work combining multi-temporal Google Earth imagery (2011–2021) with field survey data to systematically analyse spatial patterns, land-use controls, topographic factors, and catchment thresholds affecting gully evolution. The study is ambitious in scope, covers four contrasting landscapes, and demonstrates a considerable amount of careful, systematic work in assembling and interpreting the dataset.

However, several structural and conceptual issues limit the clarity and robustness of the current version.

1. Lack of coherent conceptual framework and definitions
   Key terms such as developing gully, stable gully, environmental settings, erosion risk, or forestland quality are used throughout the text but are not defined early or consistently. As a result, readers may struggle to understand the criteria the authors use when categorizing geomorphic forms or environmental attributes. Introducing clear definitions and classification rules at the outset would greatly improve readability and scientific precision.
2. Inconsistency in data presentation across the four regions
   Descriptions of the four study areas rely on different kinds of variables (vegetation cover, share of agricultural land, fragmentation, erosion risk). Because these parameters differ between regions, the reader cannot make direct comparisons. A unified, standardized set of descriptors for all four catchments is needed to enable meaningful interpretation of regional contrasts.
3. Insufficient explanation of methods and threshold choices
   Some methodological decisions—such as threshold values for hydrological extraction, the criteria used to separate “developing” from “stable” gullies, or how erosion risk was quantified—are underexplained. Because thresholds directly influence results, more justification and transparency are required.
4. Figures and maps do not always support interpretation
   Several visual elements are difficult to interpret due to overlapping categories on orthophotos, unclear legends (especially regarding which axis belongs to bars and which to lines), inconsistent naming of catchments, or ambiguous color scales. Improving figure clarity is essential, as many conclusions depend on visual comparison.
5. Interpretation of regional differences is not sufficiently grounded in environmental drivers
   While the manuscript repeatedly highlights variations between the four areas, rainfall variability—arguably one of the strongest controls on gully initiation and development—is not adequately integrated into the analysis. Without clearer reference to climatic contrasts, slope length differences, vegetation quality metrics, or land-use intensity, many interpretive statements appear speculative.
6. Overuse of absolute values without normalization
   Several comparisons use absolute numbers of gullies, total lengths, or total areas, even though catchments differ greatly in size. This makes cross-regional comparisons difficult, and in some cases misleading. Presenting relative metrics (per km², per unit watershed size) would strengthen interpretability.
7. Internal inconsistencies and missing clarifications
   Issues such as discrepancies in the number of verified gullies, inconsistent labeling (M/G/J/W), or identical catchment areas for longest and shortest gullies suggest that some parts of the data presentation require correction or further explanation.

In my view, many of the key questions addressed in this manuscript cannot be fully resolved within the analytical framework proposed by the authors. Too many environmental and anthropogenic variables interact simultaneously, and their effects overlap in ways that make clear causal interpretation extremely difficult. Furthermore, the manuscript entirely omits a discussion of soil and parent-material susceptibility to erosion. Stating that all four catchments are dominated by “black soils” is a substantial oversimplification, especially given that the authors themselves mention the presence of hills and low mountains in these regions. It is highly unlikely that all study areas share the same geological substrates, soil types, or degrees of structural stability. Without addressing these differences, the explanatory power of the analysis is weakened. Nevertheless, the empirical material collected is of high value, the dataset is rich, and the manuscript has considerable potential. I believe it is worth publishing after substantial clarification and revision. Therefore, below I provide a list of detailed comments which, if carefully addressed, should enable the manuscript to reach a publishable standard, even if some interpretative uncertainties inevitably remain.

 

line 13: better - environmental settings

line 40 - What area (in km2) does this data exactly cover? The very statement Northeastern China is imprecise.

line 47: what fo You mean by threshold process?  limit, onset, brink, edge, verge? You should use more precise word.

line 51 - lack of space

line 53 - lack of space

line 56 - the same as two previous comments

line 61 - remove dot

line 65 - area of?

line 67 - what about lenght of these slopes? it should be also important

line 80 - lack of space

line 110 - blue is not boundary but area of China

line 111 - these two are to close together - You can not say that they represent northeastern and central part of region. In my opinion both are in northeastern part.

line 120 - You provide different data for individual watersheds —sometimes vegetation cover, other times the share of agricultural land, sometimes fragmentation or an estimate of erosion risk. It's best to do this uniformly for all four areas and present this data consistently in the same summary for each area. In its current form, the reader isn't able to accurately compare them.

line 127 - how did You calculated erosion risk? What is the source of this data?

line 130 - Meihekou has 68,3% of farmland, (see line 120), why do You call it City?

line 137 - change into 8.1

line 138 - add this data (proportion of developing gullies) - for all four investigated areas

line 149 - Are all 30 gullies within the studied watersheds? Furthermore, in the case of Hailun and Baiquan, there were 10 gullies in total because both areas are within the same province? This information should be clarified.

line 163 - why there are two different satellite photos? ((remote sensing image has different than erosion gully interpretation)

line 164 - do You mean  Real-Time Kinematic?

line 171 - why there is only 14 gullies - not 30 as it was mentioned before? (in line 149)

line 172 - there is mistake - in table You used different letters - M, G, J W.

line 179 - why it is so different? 1000?

line 208 - First, you should define what developing and stable gullies are. It is enough to mention at the beginning that you separated these two categories - what criteria you adopted (how much percentage of change is enough for a gully to be developing) and how many stable and developing gullies there were in each region.

line 210 - Is it the sum of the length and area of ​​the entire gullies that have grown or just the sum of the newly formed fragments of these gullies?

line 211 - But it is due to biggest area of this watershed - so the growth rate is only valuable for interpretation - You should articulate it clearly

line 213 - one decimal place in these results will be completely sufficient and will be easier for the readers.

line 237 - the number in the case of areas of different sizes does not give a good result for interpretation.

line 242 - But this catchment area is also the largest, so without converting it by the areas of individual catchments - such results tell us little about the intensity of this type of processes.

line 297 - I can n ot understand this table - number of developing gullies - is it number of all gulies in catchment or only these which were become bigger (longer) during the period 2011-2016 and 1016-2021. If it is only about these gullies which become "bigger", does it mean that length and area - it refers to only these parts of gullies which appears, have increased) in given periods?

line 304 - Individual gully categories are very difficult to see on an orthophotomap background. It's better to simply do this on a white background with only the boundaries (black outline) showing the external boundary. A linear scale should also be added – individual catchments are on a different scale.

line 342 - this name of catchment was not used previously.

line 345 - this name of catchment was not used previously. Moreover - ditch or gully?

line 377 - The chart legend is missing information about which axis (left or right) refers to the bar part and the line part of the chart.

line 380  - The chart legend is missing information about which axis (left or right) refers to the bar part and the line part of the chart.

line 383 - The chart legend is missing information about which axis (left or right) refers to the bar part and the line part of the chart.

line 430 - Comparing these absolute values ​​in bar charts between different-sized catchments has no interpretive value. Of course, only trends in activity changes within individual catchments can be compared.

line 435 - how it is posiible that in all four pairs of gullies - 1 and 2 (longest and shortest) their catchment area is always the same? eg pair from M have 0.01 - 0.02 - both 1 and 2.

Overall, the manuscript contains valuable empirical material and the potential to make a meaningful contribution to understanding gully development thresholds. However, its scientific impact would be significantly improved by clarifying definitions, unifying data descriptions, strengthening methodological transparency, improving figure readability.

Comments for author File: Comments.pdf

Author Response

"Please see the attachment."

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript can be accepted for publishing after this revision.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

erosion gully ? should be gully, which includes "erosive" meaning. for the title maybe gully erosion is more appropriate. The study area should be "black soil region of Northeast China" in the title.

keywords: erosion gully replaced by gully erosion

Figure 1 research area location and please confirm the boundary of the black soil region of Northeast China.

Figure 2 and figures in Table 1 are not so high resolution.

please define the developing gully, stable gully and newly formed gully and reflected by some photos or remote sensing images

Figure 6,7,8,9  please provide full name of abbrev.

Table 4, the gully length is 2.34 km, 4.72 km, please provide some evidences to identify them as "gullies" not the rivers.

L545, I have not found any information about the contributions of precipitation, topography and catchment environmental conditions in your results. In addition, these limitations you listed con not really focused on your results, which seems that they could be placed in any papers about gully erosion. For reference 51, please check it right, which really states landscape patterns on gully erosion? 

Please check the latest references for your study, I do not think you have read some latest studies about gully erosion of Northea China.

Please check all sentences and ensure their readiablity and grammar correction.

Comments on the Quality of English Language

The authors should check grammar of all sentences to ensure its readiability.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have implemented a substantial part of the changes I suggested, and some of my concerns have been clarified. However, the manuscript still exhibits certain methodological limitations. In particular, the lack of data normalization to the area of the studied catchments constrains the interpretability of the results. As a consequence, the analysis remains largely inventory-based and descriptive, and only to a limited extent allows for comparisons between catchments or for identifying the factors controlling differences in the intensity of erosion processes. I also consider Figure 5 to be still unclear—the orthophoto background appears unnecessary at this map scale and reduces the readability of the figure. Nevertheless, the introduced revisions are sufficient for the article to be published; however, Figure 5 should be improved.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf