Rapid Estimation of Soil Erosion Rate from Exhumed Roots (Xiaolong Mts, China)
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Authors!
In my opinion, the study deals with a topic that may be of interest to a wider scientific community. The dendrogeomorphological approach give a new possibility for the measurement of recent soil erosion.
My suggestuions are the followings:
1. Please improve the methodology subsection: insert a map of the study site which contain the elements of a map (north arrow, scale, etc.) Also give more details about the root disk collection, because the sampling technology is not entirely clear: for example did You collect one root disk from each tree, or more root disk from one tree? Also there are some minor comments inserted in the attached document.
2. You evaluated a regression model which describe the relationship between soil erosion rate and slope steepness, but I think the R value is two low.
3. The Conclusions contain the repetition of the results of the study and also citations to other's work. You should focus more on the conclusions that can be drawn from your own work.
Also some other smaller remarks are inserted in the attached document.
Comments for author File: 
Comments.pdf
Author Response
Reply to the Reviewer 1
Dear Authors!
In my opinion, the study deals with a topic that may be of interest to a wider scientific community. The dendrogeomorphological approach give a new possibility for the measurement of recent soil erosion.
Response: Many thanks to the reviewer for taking the time to read and comment on our manuscript. Thank you for your comments, which have been taken into account in revising the manuscript. Below we respond, point by point, to the comments made in the reviewer's comments and those highlighted in the PDF. Our responses are highlighted in red.
My suggestuions are the followings:
- Please improve the methodology subsection: insert a map of the study site which contain the elements of a map (north arrow, scale, etc.) Also give more details about the root disk collection, because the sampling technology is not entirely clear: for example did You collect one root disk from each tree, or more root disk from one tree? Also there are some minor comments inserted in the attached document.
Response: The map in Fig 1 is modified taking into consideration of the comments from each reviewers. The description of the sampling procedure is extended.
- You evaluated a regression model which describe the relationship between soil erosion rate and slope steepness, but I think the R value is two low.
Response: We agree that the explained variance is relatively low. However, the F-test indicates that the fitted linear model is significant at the p=0.02 level.
- The Conclusions contain the repetition of the results of the study and also citations to other's work. You should focus more on the conclusions that can be drawn from your own work.
Response: The conclusions necessarily repeat the main results of the study, I think. It is a general rule that new information cannot be presented in the conclusion. We selected the main messages of our study in a few conclusive sentences and referred to other works only to contextualize the current findings. As far as we know it is not prohibited to cite again a few key references in the conclusion.
Also some other smaller remarks are inserted in the attached document.
lines 89-91: I think You should support more better the casual background of the topic, because maybe it is not enough reason for a scientific work that this is the first time when dendrogeomorphological methods were used in this region of China to quantify soil erosion. How many percentage of Gansu Provence is affected by soil erosion? Why soil erosion is problem in the forested areas? Why did You choose the dendrogeomorphological approach instead of other soil erosion measurement technics?
Response: Some missed information can be found in the previous sentence „Total soil loss area takes 76112 km² in Gansu Province out of which ~18% is forest and shrub….”. However, we admit that a sentence arguing for the application of the dendrogeomorphological approach is needed here, so we added a brief sentence in the revised version.
lines 95: Why Taoist shrines are important from the aspect of Your work? If not, please delete this sentence from the text.
Response: Accepted. Taoist shrines are removed from the revised text.
line 99: Are these forests natural or planted ones?
Response: The studied stand is a natural mixed pine-oak forest. This information has been included in section 2.1.
Please try to improve the quality of the map of the study area. First of all, place the components of the map on the figure: north arrow, legend, scale. Secondly, sign the border of the study site with line and not a picture, because in that case the international readers can place that site more easier in the geographical space.
Response: The missed north arrow has been placed to the lower right corner of the main map above the scale. The tree symbols which marked the sampling site in the original figure has been replaced by an ellipse encircling the sampling area.
What is not entirely clear to me is the type of soil erosion. Is there geological/natural erosion or human induced soil erosion? If the latter, what activity causes soil erosion? Are there any visible forms of soil erosion on Your study site? Gullies, small debris cones?
Response: Gullies or small debris cones were not observed on the studied slopes so sheet erosion can be assumed to be the dominant type of soil erosion and is largely caused by natural factors. It has been mentioned in a brief sentence at the end of the paragraph.
How did You collect the root disks? Did you collect one disk sample from each tree? Or did You collect more disk samples from one tree? Were the trees next to each other? Or far from each other? it is important from the aspect of erosional places, because if the trees were located far from each other, the magnitude and size of the factors causing erosion could be different!
Response: The roots were collected during a survey of several hectares of slopes. In the vicinity of the exposed roots, trees were spaced 1-4 m apart. Roots extend up to several meters from the trees, so unfortunately, for roots excavated further away from the trunk, it is not possible to clearly identify which root belongs to which tree. Therefore we cannot say that each sample belongs to a different tree, but it is very likely. A single disc sample was taken from one root.
These information have been added in a brief sentence to the first paragraph of Section 2.2.
line 210: Mass movements (slides for example) also can cause disorted accentric symmetry.
Response: Agreed. We included mass movement into the sentence.
line 280: This year is the first year when the trees grew an annual ring? The year 2002 mean that this was the last year when the roots were exhumated by the effect of soil erosion?
Response: No, 1967 was the oldest increment in which exhumation marker was observed. The earliest increment of the studied roots dates back to 19th century (see Estimated pith date of the root SSM101 and SSM130 in the supplementary table (Table S1). The year 2002 was the last increment in the studied 27 root discs with the first appearance of exhumation marker.
Comment on Table 1: slope tilt is given in degrees here, but in percentage in Fig 4. Why?
Response: Thanks for the comment. We have replaced the tilt with slope steepness in Table 1 and kept tilt in the supplementary table (Table S1).
Comment on Fig4: i think, these are too low R values, so I am not sure, that this regression model could be used as a usual one which describe the relationship between erosion rate and slope steepness
Response: We agree that the explained variance is relatively low. However, the F-test indicates that the fitted linear model is significant at the p=0.02 level.
lines 381-385: Because this sentence contains citations to other's work, this cannot follow from the results of the study. And also, these conclusions seem to me as the repetition of the results of the study.
Response: We summed up the main messages of our study in a few conclusive sentences and referred to other works only to contextualize the current findings. (As far as we know it is not prohibited to cite again a few key references in the conclusion.) The conclusions necessarily repeat the main results of the study, I think. It is a general rule that new information cannot be presented in the conclusion.
Reviewer 2 Report
Comments and Suggestions for Authors- the authors must specify the soil type or soil types in the research area, according to WRB, it is not enough to be named only as a brown forest soil;
- also it must be included a short description of the soil type from the morphological, physical and chemical point of view, in order to be undertand by the readers that this kind of soil is exposed to erosion
- some of the references included in the manuscript are too old. I am sure that can be found similar researches in the recent years. My recommandation is to be replaced, if possible: reference 27, 29, 30, 47, 52.
Author Response
Reply to the Reviewer 2
Response: Many thanks to the reviewer for taking the time to read and comment on our manuscript. Thank you for your comments, which have been taken into account in revising the manuscript. Below we respond, point by point, to the reviewer's comments. Our responses are highlighted in red.
the authors must specify the soil type or soil types in the research area, according to WRB, it is not enough to be named only as a brown forest soil;
Response: The soils can be classified as Leptic Cambisol (WRB 2006).
WRB 2006. World reference base for soil resources 2006: a framework for international classification, correlation and communication. World soil resources reports No. 103. Rome: Food and Agriculture Organization of the United Nations;
also it must be included a short description of the soil type from the morphological, physical and chemical point of view, in order to be undertand by the readers that this kind of soil is exposed to erosion
Response: The organic matter content of 15g/kg, high content of sand and silt in soil particles, poor soil structure and easy to be eroded by hydraulic action. This information has been added to section 2.1.
some of the references included in the manuscript are too old. I am sure that can be found similar researches in the recent years. My recommandation is to be replaced, if possible: reference 27, 29, 30, 47, 52.
Response: We agree that these are old papers. However, we are dedicated citing original reference for a certain statement. It is the way how we express our tribute to the scholars made great insights into the science and published seminal papers in a field.
Reviewer 3 Report
Comments and Suggestions for AuthorsAll comments and suggestions are provided in a PDF file.
Suggestions for a supplementary material table are to separate name, designation and unit row for every column. Use a broad dash for horizonatal position on the slope. In Notes add description of NA and azimuth abbreviations. Beside code column provide also “number of sample” column.
Comments for author File: Comments.pdf
Minor editing of English language required.
Author Response
Reply to the Reviewer 3
Response: Many thanks to the reviewer for taking the time to read and comment on our manuscript. Thank you for your comments, which have been taken into account in revising the manuscript. Below we respond, point by point, to the reviewer's comments and those highlighted in the PDF. Our responses are highlighted in red.
Suggestions for a supplementary material table are to separate name, designation and unit row for every column. Use a broad dash for horizonatal position on the slope. In Notes add description of NA and azimuth abbreviations. Beside code column provide also “number of sample” column.
Response: The supplementary table has been revised following these suggestions. The only exception is the suggested extra column with „number of sample” since each sample code defines a separate sample. We hope that this situation is clarified with the improvements in the descriptive part.
List of remarks and questions from the annotated PDF:
Research design is appropriate and methods are mostly adequately described with proposed minor corrections. Laboratory method with a provided criteria is well described and represented with Figure 2.. Figure 2. equation should be corrected (remove parenthesis).
Response: The unnecessary parentheses are removed from Fig 2.
Marker in conifers are well and detailedly described. Still it is not clear why only conifers' exhumation markers are described?
Response: Only conifer’s exhumation markers are described because only conifer roots were used in the study. (Three samples were collected from broadleaf roots however their ring structure was so dense that it was not possible to securely demarcate ring boundaries so those three samples were excluded from the analysis).
Field method with a provided criteria is well described. It should be emphasized which three species are sampled. I could only assume based on site description text that those are Pinus tabulaeformis and Quercus wutaishansea.
Response: Both species were sampled but the ring structure was so dense of the three samples collected from broadleaf roots that it was not possible to securely demarcate ring boundaries so only the conifer samples (n=27) were used in the analysis. It is described in the first paragraph of section 2.3.
(We note here that the binomial name of the broadleaf species is also corrected in the revised manuscript.)
Keep the units uniformly in a millimeters.
Response: The suggestion is accepted. Centimetres are converted to millimetres.
Figure 3: I suggest to reduce figure label length considering that it is been already described and referred in a above text. If there is something more in a title that is missing in previous text, than move it rather there. It is desirable that grid lines in the background of figures has know length and unit value due to better understanding of occurrence proportions.
Response: A sentence has been omitted from the description of B panel and sample codes have been moved from the caption to the figure. The same gridline is in the background of the samples in each panel, however the line spacing is a bit different in the panels due to the differences in the size and thickness of the root disks. We think that the explicitly reported gridline spacing in the last sentence in the caption (10 × 10 mm) properly helps readers understanding of occurrence proportions.
Does it should be written like this?
Response: The question mark was intended to indicate the uncertainty of the determinability of tree anatomical elements, but we accept that the term is confusing. We changed the term to "semi-ring porous".
Provide a units for all equations' parameters.
Response: Measurement unit of C, D, and ε parameters is mm. A brief sentence has been added to the end of the paragraph.
Provide an explanation for designation "U".
Response: The sentence has been rephrased eliminating the “U” designation.
Provide “number of sample” column in a Table 1.
Response: each sample code defines a separate sample. We hope that this situation is clarified with the improvements in the descriptive part.
Explain an abbreviation.
Response: The confusing abbreviation was removed from the table and the bracketed numbers are explained in the title. In addition, the unit of the variables has been added in a separate row following Reviewer’s comment on the Supplementary table.
