Soil Organic Carbon and Its Controlling Factors in the Lakeside of West Mauri Lake along the Wetland Vegetation Types
Round 1
Reviewer 1 Report
The work is relevant, since wetlands are indeed valuable types of ecosystems that have many features of the dynamics of macroelements and microelements.
The work makes a good impression. However, it is not clear whether the authors support a high level of fertilization in soils or not. Around the world, efforts are being made to reduce the use of chemical fertilizers and switch to more environmentally friendly land use. There are many known negative effects of regular fertilization, even at acceptable doses. They concern changes in the composition of soil microbiota and eutrophication of nearby water bodies. I recommend to consider these aspects in the discussion.
P. 196. "SOC was significantly greater in winter than in other seasons." Please explain this fact, make references to scientific works.
pp. 224-225 and Table 1. "Correlation analysis between SOC and soil physiochemical factors in the lakeside zone showed that most factors are closely related to SOC (P < 0.01; Table 1)". It does not make mathematical sense to calculate whether the differences between two data arrays characterizing different physicochemical parameters are reliable. It's like looking for an answer to the question: "Is there a difference between the average height of people and their weight?". You can only compare similar datasets, for example, to find out if there are differences in the accumulation of organic carbon in different years. For factors of different origin, the degree of connection (correlation) is determined, which is well shown in your work.
All the best: reviewer.
Author Response
[Comment]: The work is relevant, since wetlands are indeed valuable types of ecosystems that have many features of the dynamics of macroelements and microelements.
[Response] Thank you very much for your comment.
[Comment 1]: The work makes a good impression. However, it is not clear whether the authors support a high level of fertilization in soils or not. Around the world, efforts are being made to reduce the use of chemical fertilizers and switch to more environmentally friendly land use. There are many known negative effects of regular fertilization, even at acceptable doses. They concern changes in the composition of soil microbiota and eutrophication of nearby water bodies. I recommend to consider these aspects in the discussion.
[Response] Thanks for your suggestion. In the first version of manuscript (MS), we have actually discussed in great details on the fertilization practice in soils. For more details, please see Lines 251-260 in Section Discussion of the revised MS. In addition, we have also added some sentences regarding fertilization and eutrophication of nearby water bodies as follows: According to the report by Kristek et al. [44], microbiological preparation is better than chemical fertilizers and can reduce nitrogen fertilizers by 30%, suggesting that biofertilizer may be a good option. In addition, effective nutrient management aimed at curbing phosphorus input has cleaned up many lakes in the western world and successfully controlled cyanobacterial blooms [45, 46]. Can nutrient management helped many lakes recover from the effects of nitrogen pollution? This is a topic worthy of further study.
[Comment 2] P. 196. "SOC was significantly greater in winter than in other seasons." Please explain this fact, make references to scientific works.
[Response] Thanks for your suggestion. We have made references to scientific works and discussed the possible cause. The following sentences have been addressed in Lines 218-221 of the revised MS: This may be attributed to the inhibition effect of surface water on organic carbon decomposition. The higher water level in winter can limit O2 exchange which was largely depended by soil respiration and decomposition process, and thus accumulate more SOC [35, 36].
[Comment 3] pp. 224-225 and Table 1. "Correlation analysis between SOC and soil physiochemical factors in the lakeside zone showed that most factors are closely related to SOC (P < 0.01; Table 1)". It does not make mathematical sense to calculate whether the differences between two data arrays characterizing different physicochemical parameters are reliable. It's like looking for an answer to the question: "Is there a difference between the average height of people and their weight?". You can only compare similar datasets, for example, to find out if there are differences in the accumulation of organic carbon in different years. For factors of different origin, the degree of connection (correlation) is determined, which is well shown in your work.
[Response] Thanks for your comments. We totally agree with you that it does not make mathematical sense to compare the difference between average height and weight of people. But what we do is to explore their correlation or connection rather than differences. Thanks for your understanding.
Reviewer 2 Report
The article presents research on the content of organic carbon in soil. I recommend revision of the text. The article seems interesting and worth publishing. However, there are problems that should be cleared up. I am enclosing comments that may help in the publication of the text.
General comments:
The scope of scientific novelty of research should be clearly defined. Although the research itself seems interesting, it is local in nature and does not make a significant contribution to knowledge about the environment.
The environmental studies requires high standards in analytical methodology. Therefore, the following doubts should be clarified:
- The number of samples should be clearly indicated and the representativeness of the samples should be proven.
- All analytical procedures should be described. Validation of analytical procedure (e.eg information about basic metrological parameters –detection limits, precision, estimation of the uncertainty) should be added.
- The number of significant figures (not decimal) should be according with the metrological rules based on the validation of the analytical method.
Author Response
[Comment]: The article presents research on the content of organic carbon in soil. I recommend revision of the text. The article seems interesting and worth publishing. However, there are problems that should be cleared up. I am enclosing comments that may help in the publication of the text.
[Response] Thank you very much for your comments. We have responded to you and made the following modifications in the revised manuscript (MS) point by point.
[Comment 1]: The scope of scientific novelty of research should be clearly defined. Although the research itself seems interesting, it is local in nature and does not make a significant contribution to knowledge about the environment.
[Response] Thank you very much for your insightful comments. In order to increase the breadth of the audience or readers and also improve the width of subject of the article, we have made modification of the first paragraph in Section Introduction as follows. For more details, please see Lines 32-40 of revised MS.
[Comment 2]: The environmental studies requires high standards in analytical methodology. Therefore, the following doubts should be clarified.
[Response] Ok. We have made more explanations of analytical methodology in the revised MS according to your suggestions.
[Comment 3]: The number of samples should be clearly indicated and the representativeness of the samples should be proven.
[Response] Ok. In the revised MS, the sentences “Along each transect for each season, three soil profiles were excavated all in the location where the same covered vegetation type and the soil with a similar color were found.” and “A total of 72 soil samples (3 profiles × 4 gradients × 6 soil layers) was obtained for each season. After removing the visible roots and litter, all the soil samples were sealed in a plastic bag and then taken to laboratory. Soil samples were divided into two parts; one was air-dried for basic property determinations, and the other was used for chemical analysis.” have been added in Section 2.2.2.
[Comment 4]: All analytical procedures should be described. Validation of analytical procedure (e.eg information about basic metrological parameters –detection limits, precision, estimation of the uncertainty) should be added.
[Response] Thank you very much for your suggestion. We have supplemented and improved the analytical procedures in Lines 102-120 of the revised MS as follows: Soil bulk density and moisture content were determined using the ring knife and oven-dry method. Soil organic matter was determined by the potassium dichromate-sulfuric acid method [25]. Total N content was determined by the potassium di-chromate-sulfuric acid digestion method [26]. Samples of 5 g soil were soaked, shaken for 1 h, and soil nitrogen was extracted through addition of 5.0 ml of conc. H2SO4 and selenium catalyst, then distilled with NaOH and titrated against 0.1 mol HCl. Total P content was determined by the sulfuric acid and perchloric acid decoction method [27]. In short, total P was determined by inductively coupled plasma-optical emission spectroscopy after 5 ml of the sieved supernatants were digested in a H2SO4–HClO4 mixture. The chemical shifts were recorded relative to an 85% H3PO4 standard. Analysis of aforementioned heavy metal in soil samples were carried out as follows. The digestion was carried out with 1 g of sample in glass digestion tube of 250 ml along with 15 ml of HNO3 at 140 °C. The content was evaporated to dryness, and the dried sample treated by 3 ml of HClO4 for further oxidation from the sample solution for 30 min at 245 °C. After digestion cool the content, filter and made up to 100 ml with distilled water, heavy metals were determined with the help of atomic absorption spectrometer (Hitachi, Tokyo, Japan) [28]. Repeated measurement of soil samples have a coefficient of variation less than 5%.
[Comment 5]: The number of significant figures (not decimal) should be according with the metrological rules based on the validation of the analytical method.
[Response] Thank you very much for your comment. We have made modifications of the number of significant figures. For more details, please see main body and Table in the revised MS.
Round 2
Reviewer 2 Report
The manuscript has been revised and can be accepted.
