Impact of Wind Direction on Erodibility of a Hortic Anthrosol in Southeastern Spain

Round 1

Reviewer 1 Report

The approach for measuring sediment fluxes depending on the wind direction associated with mineralogical analyses is novel and rich in information for the management of wind erosion. Thanks also to the authors for accounting for my remarks and suggestions. 

Author Response

Dear reviewer,

 

Thank you very much for your comments, which improve this paper.

English language was checked.

Thank you very much, again, and I remain at your disposal for whatever you deem appropriate now or in the future.

 

Best regards,

Carlos Asensio

 

Reviewer 2 Report

Congratulations for this paper. There are though a few aspects that need further clarification, not sure why you sampled soils only at 5 cm depth, not clear what is the purpose of including in the analyses Leptosols and Calcisols when most of your research is made in regard to Anthrosols. Please note that Anthrosols are man-made soils, heavily (mechanically) disturbed and are highly vulnerable to wind erosion, why Leptosols and Calcisols are natural ones, very consolidated and much less vulnerable to wind erosion. Or at least give some preliminary comparisons between them based on your research. Conclusions section is very short and must be improved, you do not need to repeat what is written in the Abstract, but make the results more relevant and convincing. For a few more comments and suggestions see the file attached.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

 

Thank you very much for your comments, which improve this paper.

Now, I believe I have attended to all your indications:

 

-Line 89. “Four replicate samples were taken from the top 5 cm of soils and analyzed”.  

Now: “Four replicate samples were taken from the top 5 cm of soils and analyzed, taking into account that wind erosion processes will fundamentally affect the most superficial part of the soils”.

 

-Line 154. Table 1 also recorded characteristics of surrounding windward soils (Leptosols and Calcisols), not always completely consolidated on the surface.

 

-Line 228. The second figure has been deleted.

 

-Line 237. “…global…”

Now: “…general…”

 

-Line 253. “…is not very high…”

Now: “…is very low…”

 

-Line 267. “…high…”

Now: “…higher…”

 

-Line 275. “…to…”  has been deleted

 

-Line 282. “…windy áreas…” was included.

 

-Line 286. Conclusions section was improved.

 

 

Thank you very much, again, and I remain at your disposal for whatever you deem appropriate now or in the future.

 

Best regards,

Carlos Asensio

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The paper deals with the impact of wind direction on the intensity and composition of wind blown soil particles. The main originality of the paper is the use of a directional collector designed by the authors that allows to sample windblown sediment according of the wind direction. Mineralogy analyses allow to discuss the effect of the soil composition on the sediment flux.

However, I have questions about the quantitative approach of the integrated vertically flux. Indeed the lowest collectors is at 35 cm height so far away from the layer where most of the materialis transported  in the saltation layer. Thus the adjustement performed using equation (1) can generate large errors in the estimation of the vertically integrated sediment flux. This should be discussed, estimated and improved. For example, other equations have been proposed and could be used to estimate the uncertainties. In  the same way, a reasonalble estimate of the uncertainty of the slope of the adjustement using equation 1 (for example 10%) can be introduced to evaluate how much such uncertainty affects the estimation of the sediment flux.

-I am not sure that Mendez et al. (2011) mentioned , as indicated on line 47, that the efficiency of BSNE and MWAC increases for smaller particles.

-Is the wind direction measured during the experiment? If yes it should be useful to have the frequency of high wind speeds (for example those higher that the threshold for wind erosion) during the experiment.

Author Response

Dear reviewer,

Thank you very much for your comments, which improve this paper.

I believe I have attended to all your indications and I have tried to clarify in the manuscript those in which you indicated some ambiguity.

About your first question, even being aware of the limitations of the vertically integrated sediment flow estimation, we opted for this method because it will allow us to compare results with those obtained by other authors with the same method and similar climatic and edaphic conditions such as Basaran et al., in future works.

You are right, Méndez et al. (2011) don´t mentioned that the efficiency of MWAC increases for smaller particles.

I have included new wind data about gusts duration and direction.

Thank you very much, again, and I remain at your disposal for whatever you deem appropriate now or in the future,

Carlos Asensio

Reviewer 2 Report

This is a good research idea using an interesting new type of dust collector.

The research question remains unclear and the presented results are partly trivial, and partly not suited to answer the questions raised in the introduction. In the present form, results are not clearly presented.

The re-submission should address the following points:

• provide soil and geological maps of the study area
• use clear soil classification. Even if some of the sampled area might host Hortic Anthrosols, these are probabl not playing a major role for dust emissions as such soils usually cover only small areas. If the authors want to suggest that the whole large field hosts that soil type, I doubt it - deliver soil maps or some representative profiles of the soils that are indeed present in the area.
• provide additional photos of the area, including a view of the landscape that permits estimating the relief and vegetation, or a relief map. Relief may play a major role for prevailing wind directions.
• Is there no meterological data on prevailing winds in the area? Provide some from the nearest meterological station.
• The X-ray diffraction method delivers information about the presence of minerals. It is poorly suited for quantification statements of aeolian transport.
• How were the quantitative figures presented in table 4 calculated? There are only a few mineralogists who dare to calculate numerical results out of XRD data, and even they use ranges. The method permits only semi-quantitative results, so these figures can only be estimates.
• I don't understand tables 2 and 3.

The research design and observations are interesting - that approach certainly deserves to be followed up. However, it is a rather trivial result that more material is transported closer to the ground. That needs to be embedded in a larger picture, such as the debate on the role of local versus remote sources of dust transport.

Results of this study seem to strongly support a major contribution from local sources, and transport seems to depend largely on the prevailing wind direction. What is completely missing is the time dimension: is there no data on the time and duration of dust collection?

 

 

 

Author Response

Dear reviewer,

Thank you very much for your comments, which improve this paper.

I believe I have attended to all your indications and I have tried to clarify in the manuscript those in which you indicated some ambiguity.

About surrounding soil types, covering of Anthrosols and new images, I think is done.

I have included new wind data about gusts duration and direction.

Obtained values with the EVA program, from the Diffract Evaluation 2.1 software package, although semi-quantitative, allow to get a global idea.

I have tried to clarify what we want show in tables 2 and 3.

The duration of the experimentation has been included (24 hours)

Thank you very much, again, and I remain at your disposal for whatever you deem appropriate now or in the future,

Carlos Asensio

Round 2

Reviewer 1 Report

I am not really satisfied with the authors' response to my main comment. But, perhaps, I was not clear enough in my first review.

I will try to be more clear. Line 108 the authors write: “As the lowest collectors on the mast were placed at 0.35 m, the rate of soil lost from the ground had to be calculated empirically, by using a mathematical model predicting sediment on the soil surface ”. The use of such mathematical model is always needed when using MWAC, BNSE or other  sand traps of this type to evaluate the mass of moving sediment. However, generally the height of the lowest collector is much closer to the surface. Thus, my question was not why the authors used Equation 1 (I understood that it is  for comparison purposes) but it was: "what is the uncertainty in estimating the rate of soil lost resulting from the height of the lowest collectors which are far enough from the ground surface". As it can easily be seen from Equation 1 and Figure 5, the amount of moving sediment increases drastically when going closer to the surface. Thus, without an estimate of the sediment mass transported in the first 5 to 10 cm (as researchers using MWACs or BSNEs generally do), the constraint on equation 1 is poor leading to large uncertainties on the estimate of the amount of sediment moving   from 0 to 1.4 m. Such an uncertainty is not compatible with the numbers with four significant digits given in Tables 2 and 3 and for which no uncertainty bar is provided.

I can make a suggestion. Because the authors are interested in transported sediment, they might assume that the sedimentary material transported into the lower layer is composed of very large grains of soil that cannot be transported very far and that a good estimate of the exported material can be assessed by considering only material transported above 0.35 cm (which is not so far from the maximum height of the saltation layer, see  for example, Shao, Physics and Modelling of Wind Erosion, Springer). Thus, they can use the equation 1 to integrate the flow of sediment not between 0 and 1.4 m but between the lowest and the highest measurements they made, i.e.,  0.35 and 1.4 m. This will be more correct, with much less uncertainty and does not change the conclusions of the article, which remains an interesting and original article.

Reviewer 2 Report

These minimal revisions by the authors do not address my comments. Please see my earlier review: I requested a complete re-modeling of the paper. It is, for example, not enough to embed a satellite view of Spain and mark some dots on it in order to supply a demanded "soil map of the study area".

This is disrespect of the time invested in the review and disqualifies the manuscript from publication.