This paper investigates the saturation effect of background temperature and aridity on vegetation phenology sensitivity to urban warming across 293 Chinese cities, using multi-year MODIS and climate data. The topic is relevant to urban ecology and climate change adaptation, with clear scientific questions and reasonable methods. Below are constructive comments.

1 Abstract: The structure of the abstract needs strengthening. The beginning should clearly articulate the current gaps and limitations in quantifying vegetation phenology sensitivity to urban warming. This should be followed by a concise summary of the methodology, and finally, a systematic presentation of the results.

2 Line 61-63: The authors state that “While these studies offer empirical evidence, they do not sufficiently elucidate the underlying cause and its quantifiable relationship.”. However, based on the stated objectives, the study primarily aims to identify a so-called saturation inflection point rather than conducting an deep exploration of the underlying mechanisms. If this is the case, the Introduction needs to more clearly highlight the specific novelty and contribution of this work.

3 Line 126-128: The authors appear to define the urban center as Urban and a 20 km buffer zone as Rural. The reason for this specific delineation needs to be clearly explained in this section.

4 The figure legends require more precise descriptions. For instance, Figure 3, 9, and 10 contains panels (a) and (b), yet the current legend is imprecise and fails to clearly distinguish or explain them, and also in Figure 8, please avoid errors such as obscured numerical values in Figure 8. Therefore, the authors should be carefully verify that all other figure legends are expressed clearly and rigorously. Furthermore, given the large number of figures in the main text, please consider moving some of them to the Supplementary Materials.

5 Line 422-431: This section reads more like a summary of the Results. I recommend avoiding such redundancy. The section of Discussion should focus on analyzing and interpreting the findings rather than simply restating them.

6 Line 433-435: The study covers a large geographical area, so the word “same habitation” is confusing. Please clarify this point.

7 Line 455-457: There are instances of incorrect or non-idiomatic language. Please rephrase these sentences to ensure accuracy and readability. Given that similar issues appear throughout the manuscript, I strongly recommend a thorough proofreading and comprehensive language polishing of the entire text to eliminate errors and inappropriate expressions.

8 Line 469-470, Line 476: what’s the meaning of 50-51, and 46? Please carefully review the entire manuscript to avoid such mistakes.

9 The authors provide interpretations of the results in the Discussion section, such as the possible reasons for SOS, ECOS, and drought effect. However, these mechanistic explanations mainly rely on several literature citations without sufficient supporting data from the current study, making this part of the analysis appear weak. I recommend that the authors incorporate specific data to substantiate their inferences.

10 Line 484-488: This section also reads more like a description of the results and lacks substantive discussion. The authors should focus on interpreting the findings, exploring their implications, and comparing them with existing literature. Similarly, Line 496-500 merely repeat the presentation of results without offering in-depth analysis or discussion.

11 In Section 4.4, the authors aim to discuss the responses of phenology in different vegetation types to temperature changes and drought. While this is a valuable point, as a standalone discussion section, it appears abrupt given the study's objectives and the introduction. There is virtually no prior groundwork laid for this specific topic earlier in the manuscript. I recommend that the authors reconsider the coherence of this research point throughout the paper, ensuring better alignment between the introduction, objectives, and discussion, and provide a more in-depth exploration of these findings.

General assessment

This manuscript addresses an interesting and potentially important question: how background temperature and aridity regulate vegetation phenology responses to urban warming across a large climatic gradient in China. The dataset is broad in spatial extent, and the topic is relevant to urban ecology and climate-change research. However, in its current form, the manuscript requires substantial revision before it can be considered for publication.

My main concerns are as follows. First, the conceptual framing is not yet sufficiently sharp, particularly regarding the definition and justification of the proposed “saturation effect.” Second, several key variables and methodological choices remain insufficiently defined, especially the roles of preseason temperature (T), land surface temperature (LST), aridity index (AI), and the derivation of sensitivity metrics such as Rt-SOS and Rt-EOS. Third, the Results and Discussion sometimes overinterpret fitted nonlinear relationships as evidence for a mechanistic saturation process, without sufficiently ruling out alternative explanations or model forms. Finally, the manuscript contains numerous language problems, unclear expressions, and some formatting/symbol issues that reduce readability and scientific precision.

Major comments

1. The Abstract contains several interesting findings, but key points remain unclear. In particular, it is not sufficiently clear how the reported SOS and EOS responses are linked to the proposed “saturation effect.” The abstract should explain whether saturation refers to phenological timing itself, to temperature sensitivity, or to the urban warming effect. The biological meaning of negative and positive values such as negative ΔSOS and positive ΔEOS should also be stated explicitly. In addition, the rationale for replacing T with LST is not clear in the abstract, and the broader ecological significance of the study is not clearly highlighted. At present, the abstract reports many numbers and relationships, but the main take-home message remains diffuse.

Introduction：

2. The manuscript introduces a potentially interesting central idea, namely that the response of vegetation phenology to urban warming may weaken or approach saturation under warmer background conditions. However, the scientific gap is not yet articulated clearly enough, and the novelty relative to previous urban phenology studies remains insufficiently developed. The Introduction should explain more explicitly what previous studies have already established and what remains unresolved, especially regarding nonlinear responses, threshold behavior, and the combined role of background temperature and aridity. At present, the logic from literature review to study objectives is not fully convincing.

3. One of the most confusing aspects of the manuscript is the use of multiple temperature-related variables. The manuscript uses preseason air temperature (T), land surface temperature (LST), and urban warming-related differences, but their ecological meanings and analytical roles are not clearly distinguished. T appears to be used to quantify phenological sensitivity, while LST is treated as background climate and later used to derive thresholds. The rationale for replacing or translating T into LST is not explained clearly enough. The manuscript should clarify why T is used in one part of the analysis, why LST is used in another, how these variables differ ecologically, and how directly comparable they are. This issue affects not only the Methods, but also the interpretation of the Results and the conclusions.

4. Several parts of the Introduction should be revised for logic and clarity. The statement in L57–58 that background temperature heterogeneity may disrupt phenology responses to urban warming is not adequately supported by the examples that follow. The subsequent sentence in L64–65 is largely repetitive of the same idea. In addition, the expectation stated in L9–83, namely that urban warming benefits in warmer regions will gradually approach saturation, is a central hypothesis of the study but is introduced too directly and without sufficient literature support. If this hypothesis is important, it should be built on a stronger review of relevant studies from warm regions and on more explicit evidence for nonlinear or weaker responses under warm conditions. Also, although the manuscript is centered on urban warming, the first several paragraphs devote relatively little space to why urban environments provide a distinct and useful context for testing phenological sensitivity.

5. The drought/aridity paragraph in the Introduction is informative, but it reads somewhat as a parallel topic rather than a fully integrated part of the main conceptual framework. If aridity is one of the two key regulators in the study, then it should be tied more explicitly to the urban warming question from the outset. The final sentence of that paragraph is also rather broad and reads more like a conclusion than a hypothesis. The manuscript would benefit from stating more explicitly how and why aridity is expected to interact with warming-related phenological responses in urban versus rural settings.

Methods：

6. The notation for ΔRt-SOS and ΔRt-EOS is internally inconsistent: the text refers to the 10th buffer zone at 20 km, but the equations use notation such as Rt-SOS(20), which could be misread as a buffer index rather than a distance. This should be standardized and clarified.

7. Since the concept of “saturation effect” is central to the paper, the authors should explain why a logistic function is appropriate and compare it with other nonlinear alternatives, such as quadratic, segmented, or generalized additive models. At present, the fitted logistic relationships are treated as support for saturation, but this remains incomplete without comparative model testing.

Results and Discussion：

8. The Results section reports several threshold values, but the relationships among them are unclear. For example, Section 3.2 suggests that urban-rural differences in SOS and EOS weaken or even reverse when LST exceeds 12 °C or 18.5 °C, whereas elsewhere thresholds such as 12.5 °C and 4 °C are emphasized for LST-regulated sensitivity. These thresholds may correspond to different response variables, but this is not made sufficiently clear. The manuscript should distinguish much more explicitly between thresholds for phenological dates, thresholds for urban-rural differences, and thresholds for phenological sensitivity.

9. Section 4.4 attributes vegetation-type differences mainly to broad functional traits such as drought resistance and resource-use strategy. While these interpretations are reasonable in general ecological terms, they remain fairly generic given that the manuscript uses broad vegetation categories and does not directly measure traits. This subsection should therefore be written more cautiously and tied more closely to the actual scope and limitations of the dataset.

10. There are many grammatical problems, awkward expressions, unclear symbol definitions, and even some formatting or rendering issues. Examples include ambiguous wording, inconsistent notation, and sentences whose meaning is difficult to interpret. These are not merely stylistic concerns; in multiple places they reduce scientific precision and make the logic harder to follow. I strongly recommend careful language revision of the full manuscript, including clarification of all abbreviations, symbol definitions, equations, and units.

Minor comments

1. The statement in L88–89 could be rephrased more clearly. A wording such as “A pronounced delayed SOS was documented on the Yungui Plateau under preceding drought conditions” would be more natural.
2. The transition from the background review to the study objectives is abrupt and should be made smoother.
3. The AI equation is not displayed clearly enough, making it difficult to determine whether AI is defined as P/PET or PET/P. This should be corrected.
4. The authors should report how much data were excluded during phenology preprocessing and quality control.
5. Figure 2 needs improvement in visual clarity. The inset panels are too small and the y-axis in the inset appears partially obscured or overlapped, making the embedded comparisons difficult to interpret. Since these inset plots support key claims regarding spatial contrasts, they should be enlarged and reformatted for readability.
6. Several expressions in the Results reduce clarity and should be revised, for example “logistic trends was observed,” “positive related,” “the higher of AI,” and “negative ΔEOS tended to appeared.”
7. The manuscript should explicitly state the biological meaning of positive and negative ΔSOS and ΔEOS whenever these metrics are introduced and discussed.
8. The significance and ecological contribution of the study should be stated more explicitly in both the Abstract and the Discussion. At present, the manuscript reports many statistical relationships, but the main conceptual advance is not always clearly conveyed.