The Effect of Soil Conservation Measures on Runoff, Soil Erosion, TN, and TP Losses Based on Experimental Runoff Plots in Northern China
Round 1
Reviewer 1 Report
I added several comment to the manuscript as PDF notes
some parts are missing and a connection to general context are missing too, in order the paper to be sounding and interesting for international readers.
Comments for author File: 
Comments.pdf
Author Response
Dear reviewer,
Great thanks for your valuable suggestions and/or comments on the manuscript PDF file, detailed responses were listed below.
1, I would move this section out of material and methods move to a separate "study area" section
Response: This may be a selection. However, in most of the published papers, the “study area” or similar descriptio was within the section “Materials and methods” as a subsection. Therefore, in my opinion it is better to stay its current status.
2, Please cite the appropriate bibliography to support this sentence
Response: Yes, a reference is needed here. One reference (see “Fang, 2021” in the reference list) was added in the revised manuscript.
3, For figure 1, some comments were given.
Response: The whole of China was inserted the figure. The north arrow was moved to the upright corner. The grey line that represents the boundary of Beijing city was added too. A hillshade image in transparency was also made in the revised manuscript. Figure 1b was replaced, and the meanings of the numbers were given in the caption. Furthermore, in Figure 1, numbers of 11, 21, and 22 were added.
The single distribution of gneiss cover with very less other lithology of the catchment does not look well, and it does not influence our research results. Therefore, a reference was added here to support the comment in the revised manuscript, without adding the lithological image.
4, For 2.2 section: an introduction summarizing he general approach of the study and an overview of the methods; and check for formatting of the figures throughout the text
Response: At the beginning of this section, a summarization was given introducing the method of the current study. Yes, the formatting of the figures were checked throughout the manuscript.
- In figure 1 I do not see numbers 11, 21, and 2
Response: Yes, they were not labelled. In the revised manuscript, they were added into Figure 1.
6, For “taled” ? i do not understand.
Response: It is “totalled”, two letters “to” was before the words. It was corrected in the revised manuscript.
7, For rainfall event in 2.3 section, “see comment above in the study area a more detailed climatological and metereological overview is needed Which event are you talking about? What do you mean for heavy rainfall event; which intensity, which cumulate rainfall, which duration?”
Response: Good.The climatological and metereological overview during the study period was added, and the rule for the selection of the 57 rainfall events used in the present study was given. In this manuscript, the rainfall events that generated runoff were not further classified. The word “heavy” rainfall event was not used because the rainfall types were not classified in the present study.
8, For the measure method of TN and TP, the comment “Please define it properly or cite the relative references”
Response: Yes, a reference was given in the revised manuscript.
9, specify the rainfall guage
Response: Yes, time resolution of the measurement by rainfall gauge was given.
10, For 2.4 section, the comment “When a method is mentioned, whether it is a statistical analysis or a soil erosion analysis, it should be briefly described or at least a bibliography should be cited in which this method is adequately described and explained”.
Response: It is a good suggestion. A bibliography was given for the statistical method in the 2.4 section of the revised manuscrpt.
11, For 3.1 “Fig.3”, comment” this graph should be explained more clearly”.
Response: Thanks. More explanation was given in the revised manuscript.
12, How was the percentage of erosive rain calculated? Please define it appropriately.
Response: The method of the percentage was given.
- the unit “t km-2 event-1” comment” not clear”.
Response: In order to avoid misunderstanding, it was rewritten as “The highest event-averaged SLR of 444.4 t km-2 occurred”.
- For Figure 4a, comment “check this label”
Response: The label “Runoff depth” was corrected.
- Honestly I'm lost here. I don't understand what the numbers in brackets represent or what is the difference between the number outside and inside the brackets and finally I don't understand what the letter represents!
Response: The numbers outside the brackets were mean values, and those in the brackets were standard deviation. The letters indicated the difference judgement among the mean values. These information were added in the revised manuscript.
- Why all this empty space?
Response: This format is made, and may be changed later.
17, For the discussion section, the comments” check discussion section according to the previous comments; connect your results and discussion to the climatic and metereological conditions in the area. This could connect your study to a more general climatic condition and could improve the relevance for international readers”
Response: This is a very good suggestion, according to the climatic and metereological conditions, a Pearson correlation coefficients matrix was added, and correlation analysis between five rainfall eigenvalues and runoff and soil loss rate was further given to connect the results to the discussion with the climatic and metereological conditions
18, For table 3, comments” What do they represent?” .
Response: They represent significance at the 0.01 level. This information was given in the revised manuscript.
- For Figure 7, the comment “this should be introduced in the study area overview”
Response: I think it may be ok. However, here, we emphasize the impact of soil conservation measures, and deduce the requirement to implement water-saving measures at the end of the discussion. Therefore, this figure stayed at the original place.
20, For results, comment “as mentioned above (see comment in the discussion section) also the conclusions should be more related also to a general context (similar climate geological landuse conditions) or in general connected to a general overview in order to be more attractive to international readers.”
Response: Yes, connected to the previous results and discussions, impacts of rainfall on runoff and soil loss as well as future study requirement were added in the “Conclusions” section.
Except for the comments listed above, other errors including adding a comma and others in the .pdf file were also corrected.
Reviewer 2 Report
The paper describes results of 5 year (2014-2019) measurements of runoff, soil erosion, (particulate) TN and TP from 18 runoff plots in an experimental station in Northern China. The plots (5 m width x 10 m length) differed for land use (bare soil, annual crops, grass, perennials), soil and water conservation measures (contour tillage, terracing), and slope. The paper is interesting because it is always important to report field-scale measurements that can provide further evidence of best management and land use, thus confirming effectiveness of Best Management Practices. The case is relevant as the region is in a watershed of a reservoir that supplies drinking water to Beijing, and for which nutrient pollution is reported as a major water quality issue. The paper is in general well written, however a read proof of native English speaker is recommended.
Before publication the author should however address some issues:
1) I believe an ANOVA type of analysis (or something on these lines if variables do not meet anova requirements of normal distribution type) should be run for this dataset. The way the data is presented now does not allow to derive effects of land use, soil and water conservation measures, or their interactions, and slope is a confounding factor. With 18 plots, 5 years of measurements and more than 50 events, this type of analysis should be possible and indeed important for the objective of the paper.
2) TN and TP losses are only derived from particulate form. The author uses then some previous work on N and P losses in dissolved forms (ref 28), however this must be better presented in the M&M. Table 5 is not part of the current work, and should be presented earlier; the relevance of this dataset for the current work should be explained and expanded. On the same line, how is figure 6 calculated? This should be better explained, at the moment it’s very confusing, but the figure ss important to assess total nutrient losses from the plots, which is the main focus of the paper.
3) the role of slope is not commented on at all. But it is clearly important and plots have slopes ranging from 3,5 to 27 (degrees?). Please in Table 1 remove Length and Area as these are constant that can be reported once in the text (and also in the caption if you like). Please add units of measures where relevant in the table.
3) table 4: what is the use of regressions for each plot? I would have expected maybe equations for each land use, maybe in a graph showing the scatter. As it stands now, Table 4 if of very little use. Equations based on land use, slope, and SWC would be more useful
4) bar plots with error bars (are these error bars, please specify in the captions) are welcome, however these should not go into negative, which has no physical sense.
5) Figure 8: I believe it’s incorrect to present data in this way: lines between the points should not be present as plots were not connected. The labelling of plots in X axis does not convey information about relevant factors (e.g. land use, slope, etc), and referring continuously to table 2 is clumsy, please rearrange. Also, what is a -20% efficiency? What was used as basis for calculating the reduction efficiency? Please explain better in the work.
6) in M&M, please add that work was conducted in an experimental station, providing some more details. More information on soil type(s), like permeability, depth, would be very useful for international literature. Information on total area of the watershed would be useful too. The choice of land uses seems at odds compared to main land use types in the plots, please give a rationale. What is economic forest, a plantation?
7) please use and refer to these two work as they are very relevant for this paper to put the paper in relation to international literature:
Maetens, W., Vanmaercke, M., Poesen, J., Jankauskas, B., Jankauskiene, G., Ionita, I., 2012. Effects of land use on annual runoff and soil loss in Europe and the Mediterranean: a meta-analysis of plot data. Prog. Phys. Geogr. 36, 599–653.
Cerdan, O., Govers, G., Le Bissonais, Y., Van Oost, K., Poesen, J., Saby, N., Gobin, A., Vacca, A.,
Quinton, J., Auerswald, K., Klik, A., Kwaad, F.J.P.M., Raclot, D., Ionita, I., Rejman, J., Rousseva, S., Muxart, T., Roxo, M.J., Dostal, T., 2010. Rates and spatial variations of soil erosion in Europe: a study based on erosion plot data. Geomorphology 122, 167–177.
8) Figure 1: the brown line is not presented in the legend. Is this the reservoir watershed?
9) using acronyms H, ASLR does not help much manuscript readability. In many cases I’d prefer to read the word instead, maybe the acronyms can be used in tables only.
10) finally, as figures provide lots of information, I suggest that maybe adding cumulative curves of plots losses (runoff, soil, TN and TP) in time could be very effective. All plots could possibly stay in it. Just a suggestion.
Author Response
Dear reviewer,
Great thanks for your valuable suggestions or comments, detailed responses were listed below.
1) I believe an ANOVA type of analysis (or something on these lines if variables do not meet anova requirements of normal distribution type) should be run for this dataset. The way the data is presented now does not allow to derive effects of land use, soil and water conservation measures, or their interactions, and slope is a confounding factor. With 18 plots, 5 years of measurements and more than 50 events, this type of analysis should be possible and indeed important for the objective of the paper.
Response: Yes, it is a good idea. The effect of soil and water conservation measures has been determined using LSD test which is a kind of ANOVA analysis. The ANOVA was used to detect the differences of the mean values of runoff, soil loss rate, TN and TP between and among each treatment. The information was given in Table 2, and Figures 4 and 5.
2) TN and TP losses are only derived from particulate form. The author uses then some previous work on N and P losses in dissolved forms (ref 28), however this must be better presented in the M&M. Table 5 is not part of the current work, and should be presented earlier; the relevance of this dataset for the current work should be explained and expanded. On the same line, how is figure 6 calculated? This should be better explained, at the moment it’s very confusing, but the figure so important to assess total nutrient losses from the plots, which is the main focus of the paper.
Response: Thanks for your valuable suggestions. Detailed information on Table 5 was given in Materials and Methods section, and Table 5 was moved into this section and renamed as Table 2 in the revised manuscript. The data source of particulate TN and TP contents were carefully given in “2.3 data collection” section, and the method to calculate particulate TP and TN contents as well as their respective contributions to the total were added in the “2.4 data treatment and statistical analysis” section in the revised manuscript.
3) The role of slope is not commented on at all. But it is clearly important and plots have slopes ranging from 3,5 to 27 (degrees?). Please in Table 1 remove Length and Area as these are constant that can be reported once in the text (and also in the caption if you like). Please add units of measures where relevant in the table.
Response: Thanks for your suggestion. The “Length” and “Area” columns were deleted from Table 1, and the unit of slope degree was added. Furthermore, some comments on slope degree were added in the “Discussion” and “Conclusion” sections of the revised manuscript.
4) Table 4: what is the use of regressions for each plot? I would have expected maybe equations for each land use, maybe in a graph showing the scatter. As it stands now, Table 4 if of very little use. Equations based on land use, slope, and SWC would be more useful.
Response: Thanks. In my opinion this table can show the effect of runoff depth on TP and/or TN loss. According to the valuable suggestion, the equations between runoff depth and TN and/or TP for the six land use types (i.e., bare, cultivated land, orchard land, grass, shrub, and forest lands) were generated. Slope was not considered in the table because for some land use types (e.g., orchard), only two slope gradients existed, and for forest, only one slope degree since plots 8 and 10 were not included when regression functions were generated.
5) Bar plots with error bars (are these error bars, please specify in the captions) are welcome, however these should not go into negative, which has no physical sense.
Response: Thanks. The negative parts of the bars were deleted from the plots.
6) Figure 8: I believe it’s incorrect to present data in this way: lines between the points should not be present as plots were not connected. The labelling of plots in X axis does not convey information about relevant factors (e.g. land use, slope, etc), and referring continuously to table 2 is clumsy, please rearrange. Also, what is a -20% efficiency? What was used as basis for calculating the reduction efficiency? Please explain better in the work.
Response: Thanks. For the plots 8 and 10, no runoff was generated, implying the interception efficiencies were 100%. Therefore, lines should be connected here. This was revised. An explanation for the labeled numbers in X axis was given in the caption, and similar explanations were also done for other figures. The mean event values of soil, TN, and TP losses from the bare plots 3 and 4 were used as basis for calculating the respective reduction efficiencies for other plots. This information was added in the “Materials and Methods” section in the revised manuscript.
7) In M&M, please add that work was conducted in an experimental station, providing some more details. More information on soil type(s), like permeability, depth, would be very useful for international literature. Information on total area of the watershed would be useful too. The choice of land uses seems at odds compared to main land use types in the plots, please give a rationale. What is economic forest, a plantation?
Response: Yes. Information on soil type, soil depth, and soil saturated hydraulic conductivity was added in the revised manuscript. The total area of the small catchment was also given in the 2.1 section.
According to the suggestion, the land use types were rewritten. The economic forest is Chinese chestnut. This information was added in the revised manuscript.
8) Please use and refer to these two work as they are very relevant for this paper to put the paper in relation to international literature:
Maetens, W., Vanmaercke, M., Poesen, J., Jankauskas, B., Jankauskiene, G., Ionita, I., 2012. Effects of land use on annual runoff and soil loss in Europe and the Mediterranean: a meta-analysis of plot data. Prog. Phys. Geogr. 36, 599–653.
Cerdan, O., Govers, G., Le Bissonais, Y., Van Oost, K., Poesen, J., Saby, N., Gobin, A., Vacca, A.,Quinton, J., Auerswald, K., Klik, A., Kwaad, F.J.P.M., Raclot, D., Ionita, I., Rejman, J., Rousseva, S., Muxart, T., Roxo, M.J., Dostal, T., 2010. Rates and spatial variations of soil erosion in Europe: a study based on erosion plot data. Geomorphology 122, 167–177.
Response: Very good references. Thanks. They were added in the reference list and in the text in the revised manuscript.
9) Figure 1: the brown line is not presented in the legend. Is this the reservoir watershed?
Response: The brown line is the boundary of Beijing. It was added in the revised manuscript.
10) using acronyms H, ASLR does not help much manuscript readability. In many cases I’d prefer to read the word instead, maybe the acronyms can be used in tables only.
Response: Thanks. H and ASLR were replaced by “runoff depth” and “annual SLR” in the revised manuscript.
11) finally, as figures provide lots of information, I suggest that maybe adding cumulative curves of plots losses (runoff, soil, TN and TP) in time could be very effective. All plots could possibly stay in it. Just a suggestion.
Response: Thanks for your suggestion. I find it difficult to add cumulative lines for most figures, and cannot provide more information too. Therefore, accumulative lines were not added in the revised manuscript.
