the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Aug 2025
The influence of snow cover dynamics on gross primary productivity of cultivated land in Northeast China
Abstract. Snow cover is a crucial factor influencing gross primary productivity (GPP), but the various regulatory mechanisms across different geographical zones in Northeast China remain unclear. This study comprehensively analyzed the dynamic changes in snow cover and GPP in Northeast China from HY2001 to HY2020. Specifically, the study area was divided into six subregions to investigate the impact of snow cover on cropland GPP. The results revealed that the snow water equivalent (SWE) decreased in 63 % of the croplands in Northeast China, while the snow cover duration (SCD) increased in 54 % of the croplands. Additionally, delayed snow cover end dates (SCEDs) were observed in 61 % of the croplands, with 74 % showing significant increases in cropland GPP. In terms of cropland types, SCD showed the strongest positive correlation with dry lands, while paddy fields were more sensitive to SCED variations. Geographically, the Changbai Mountain, Sanjiang Plain, and Khingan Ranges exhibited more pronounced GPP changes due to SCED. In contrast, the Liaohe Plain and Western Sand Area were predominantly affected by SWE, while the Songnen Plain showed greater sensitivity to SCD. These findings elucidate the critical role of snow cover in modulating cropland GPP variations across different geographical zones, providing valuable insights into the influence of similar climatic conditions on cropland ecosystems.
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Status: open (until 14 Oct 2025)
- RC1: 'Comment on egusphere-2025-2951', Anonymous Referee #1, 07 Sep 2025 reply
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RC2: 'Comment on egusphere-2025-2951', Anonymous Referee #2, 02 Oct 2025
reply
The manuscript presented a detailed study on the impact of snow on the cropland gross primary productivity in northeast China, by using dataset retrieved from satellite remote sensing and reanalyzes and others. The topic is interesting, as the structure is clear together with the logic. However, a main problem of the current version is the absence of physical mechanisms because most explanations are based on statistical analysis. In addition, I have some specific comments as below, and hope the authors can still improve the manuscript accordingly.
- In the second paragraph of the introduction section, a summary on the previous studies on the impact of snow on GPP was presented. How about the associated study in the northeast China? I think the readers would wonder if there is any existed studies in the same area.
- In figure 1, the six sub-regions in figure 1c is hard to clearly see. And in the context, only the climate features of northeast China was introduced, how about the six sub-regions? What do you mean “distinct climatic characteristics across these six sub-regions”? More explanations are necessary.
- In the method section, I think it may be not necessary to present all statistical algorithms because some of them are widely-employed ones. Besides, the spatial and temporal resolutions of these data are different, how to interpolate them into the same grids? And will that interpolation introduce any associated uncertainty into the analysis?
- From section 3.1, spatiotemporal distribution of snow cover is more suitable for the manuscript than “snow cover dynamics” in the title, because the latter is within a small scale as I see.
- I do not like the titles of section 3.2 and 3.3. Both are in the style of the relationship between A and B. However, the logical relation between A and B is not clear. I mean who is the reason and who is the result. For example, “the relationship between snow cover and soil properties” is somewhat amazing. Snow cover is associated with climate and weather, but soil property is by land surface. Does A decide B? or B decide A? If we only give some statistical results between A and B rather than the physical mechanism between them, this is only a mathematical game.
- I suggest the authors can add a short paragraph between section 4 and 4.1 to tell why and what will you do in the discussion section, and what is the logic among the three sections below.
- I suppose to see more physics in the section 4.3, but it is a pity that there are still some mathematical analyses rather than physical explanations. For example, “In the Changbai Mountain agroecosystem, the snow cover-ST-GPP pathway exhibited a significant indirect effect (βsnow-ST × βST-GPP = –0.67 × 0.76 = –0.51), indicating that snow cover suppressed photosynthetic efficiency through thermal limitation mechanisms during the growing season.” What I want to know is why and how the snow cover suppressed photosynthetic efficiency through some physical mechanisms.
Citation: https://doi.org/10.5194/egusphere-2025-2951-RC2
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This study analyzed the dynamic changes in snow cover and cropland GPP in Northeast China from 2001 to 2020. The need for such a study is well justified and the authors cite ample relevant literature, but there are many issues, including the title, data, method, and structure, need to be revised before consideration of acceptance.
My first comment is that the cropland GPP is largely influenced by human cultivation, then how can you judge the change of cropland GPP is result from snow cover change? Furthermore, the cropland is divided into dry land and paddy field. The GPP of paddy field is mostly controlled by irrigation, then how can you judge the change of paddy field GPP is result from snow cover change?
My second comment concerns the data selection and the reliability of the analysis: the manuscript does not clearly specify whether the data used are annual data or from specific months. Moreover, the snow cover period and the crop growing season are not synchronized, so it is unclear what the “direct effect” mentioned in the paper refers to. Additionally, the study divides the area into six geographical regions for analysis; however, in some regions, croplands account for only a very small proportion. Conducting further analyses on these regions and comparing them with others raises concerns about the reliability of the results.
My third comment concerns the research rationale, logical consistency, and methodological limitations: the manuscript briefly mentions that the impact of snow cover on GPP exhibits spatial heterogeneity across different vegetation types, but it does not clearly justify why the study focuses specifically on cropland GPP as the research object. Additionally, the partial correlation analysis between snow cover and soil characteristics lacks logical connection to the exploration of the snow–GPP relationship, and there is no clear mechanistic discussion provided afterward. Furthermore, the methodology in Section 4.2 has significant limitations: it directly infers “threshold effects” and a “causal relationship” between snow cover and GPP from scatter plots and smoothed curves, which can easily lead to over-interpretation and potential misrepresentation. Since GPP variations are influenced not only by snow cover but also by other climatic factors (e.g., temperature, precipitation, and radiation), the manuscript should clarify how the effect of snow cover was isolated from other environmental influences.
My fourth suggestion is to revise the use of English language and grammar, while it is largely satisfactory overall, there are multiple linguistic issues throughout the whole manuscript that need to be revised, preferably by someone with a solid knowledge of English grammar. E.g., in line 35, “play are pivotal role” should be “play a pivotal role”.
Furthermore, there are a few important and minor comments/mistakes that are listed below and should be considered.