Hyperspectral Estimation of Soil Organic Carbon Content Based on Continuous Wavelet Transform and Successive Projection Algorithm in Arid Area of Xinjiang, China

Round 1

Reviewer 1 Report

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1.      It is specifically mentioned in the title that it was made in Xinjiang, but the Introduction does not say why it was made in Xinjiang. Is there any special place or different method or background from other places?

2.      What do the abbreviations CWT and SPA refer to in the Abstract?

3.      Line 107, from the plant growth, I can't feel that salinization is very serious in this region.

4.      Line 134-140 can be supported by literatures?

5.      I can't see Line 198 clearly.

6.      In Fig. 2a, it is suggested to add scatter points on the graph to facilitate the observation of their distribution. The spectrum at the top of Fig. 2b is obviously different from other spectra. Is there any special treatment?

7.      Fig. 6 Data verification, whether the discrete distribution between the measured value and the verified value indicates a large difference.

8.      At present, there have been many researches on soil organic matter estimation by hyperspectral method, which has developed from the field spectroscopy to the upper air spectrum or remote sensing spectrum. From the conclusion, the two new algorithms are helpful to improve the prediction results. They should still be based on the traditional ground object spectrometer, which is not convenient for large-scale and large area prediction.

9.      Check the format of the references.

Author Response

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Reviewer 2 Report

sustainability-2167178: This manuscript is well done and interesting. However, some general issues must be revised.

1) Line 20: “CWT” should be mentioned full name at the first place in the abstract.

2) Line 22: “SPA” should be mentioned full name at the first place in the abstract.

3) Introduction, Lines 36-38: the roles and how important of SOC are barely mentioned. Please explain more details such as enhancing crop yield, improving soil properties, mitigating GHG emission and enhancing ecosystem services, so on. Please see these papers. [Soil Organic Carbon in Sandy Paddy Fields of Northeast Thailand: A Review. Agronomy 2020, 10(8), 1061.] [Six Stabilization Mechanisms of SOM Implications for C Saturation of Soils. Plant Soil 2002, 241, 155–176.] [Carbon footprint and predicting the impact of climate change on carbon sequestration ecosystem services of organic rice farming and conventional rice farming: A case study in Phichit province, Thailand.  Journal of Environmental Management 2021, 289, 112458.].

4) Introduction, Lines 81-91: Please explain more clearly about the research gaps, as well as the contribution of this study.

5) Line 110: What type of crop in cropland?

6) Line 119: Did you measure bulk density?

7) Line 119: The equation for estimating SOC is required.

8) Figure 1: What type of land for sub-figs (b), (c), (d) and (e)?

9) Soil texture of each landuse type should be reported, which may be affect the refection.

Author Response

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Round 2

Reviewer 1 Report

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1. Conclusions in line 548. The SPA preferred characteristic wavelengths were mainly at the high decomposition scale (2⁶~2⁹). Is there a unit for the decomposition scale?

2. Check the format of the references.

3. Check the syntax and logical structure.

4. Fig 5. the labels on the bar chart are not clear enough.

Author Response

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Reviewer 2 Report

Accept in present form

Author Response

We are very grateful to the reviewers for the positive comments on our work!