Spectral Mixture Modeling of an ASTER Bare Soil Synthetic Image Using a Representative Spectral Library to Map Soils in Central-Brazil

Round 1

Reviewer 1 Report

General comments

The work explores the development of digital soil maps (DSM) in bare soils, from a short time series (3 years) of ASTER multispectral images, a limited number of conventional soil profiles, conveniently classified according to the Brazilian system and a viewable data library. -infrared spectra generated from surface materials of the same soils. The authors explain in detail the methodology used, the problems and limitations encountered at each stage and adequately evaluate the final result of the proposed methodology. I think it is a well-written, detailed, and interesting work for a wide range of readers, including non-specialists in the field. In my opinion, it should be published with some minor modifications.

Among them, I would cite as most relevant 1)those related to the structure of the work and 2) the need to include an explicit additional discussion on the limitations of the work and necessary future developments, perhaps as an additional section in the discussion, since there is only a brief reference in the conclusions.

For example, it seems clear that results will be better the higher the correlation between the surface characteristics of the soil on which information is acquired and the subsurface characteristics that determine soil classification. Or between the latter and some “3D indicator” that is related to the subsurface characteristics of interest (slope, aspect, geology...) or that is significantly influenced by their presence (water accumulation, vegetation or land use).

It is also clear that the expert integration of all these potential indicators of subsurface soil properties is necessary, together with subsurface observations of different intensity (boreholes, test pits) to be able to extrapolate and come up with maps that are (distantly) comparable to those of the old pedologists.

On the other hand, since soil classification is often based on arbitrary ranges of certain subsoil characteristics, in many cases it will be quite difficult to determine the extent of certain categories (eg, Ferrasols/Plinthosols) without having sufficient information collected on the ground.

Specific comments

Introduction

Clear and well documented. Well established goal.

Material and Methods

Detailed, clear and well-structured description.

p. 5, Line 189, “by MESMA” repeated

Results / Discussion

These sections appear separate but, in fact, the Discussion section includes many numerical and cartographic results mixed with the discussion itself.

In my opinion, the Results section should include the results with minimal descriptive comments and the discussion should be dedicated to evaluating and discussing these results in the context of previous literature and in relation to the proposed objectives. In relation to this, a subsection dedicated to the limitations of the work and possible future developments is missing.

P. 7, Table 1 footnotes. The explanation of the codes 3 and 4 have been changed.

Conclusiones / Abstract

The conclusions are OK. Some mention of the limitations of the study is missing in the abstract.

Author Response

Dear reviewer.

We inform you that we followed your suggestions that contributed to the article's improvement. We record the changes in red throughout the text.

Regarding the observation about the results section, we justified the format by balancing the information in the text since including the entire discussion in a single section would unbalance it. We could suppress and summarize the results but risk missing crucial information.

Another point you pointed out is the description of the limitations of the work and suggestions for future work. We inform you that at the end of the discussion section (p. 15, l. 428-455), we have inserted a topic, "3.7. Limitations and perspectives", which deals with the difficulties we identified, and the limitations rightly pointed out by you, as well as what strategies could be adopted to overcome these limitations.

In addition,

We state novelties and stages of study at the end of introduction of manuscript at (p. 2, l. 77-82).

We have added relevant numerical results to the end of the abstract (p. 1, l. 27-28).

Table 1’ footnote was adjusted ( (p. 1, l. 239).Table 2 and Table’s numbers was reviewed (p. 1, l. 333 and 366).

Furthermore, we are grateful for the practical interventions and comments on our work.

Reviewer 2 Report

This manuscript needs to following minor modifications:

1- Authors did not state novelties and stages of study at the end of introduction of manuscript.

2- Authors did not important results quantitatively in abstract.

3- Conclusion of manuscript is very short. Authors should add limitations and recommendations for future studies to conclusion. They did not compare obtaind results with results of other studies in this region.   

Author Response

Dear reviewer.

We inform you that we followed your suggestions that contributed to the article's improvement. We record the changes in red throughout the text.

1- Authors did not state novelties and stages of study at the end of introduction of manuscript.

We add (p. 2, l. 77-82) the information indicated.

2- Authors did not important results quantitatively in abstract.

We have added relevant numerical results to the end of the abstract (p. 1, l. 27-28).

3- Conclusion of manuscript is very short. Authors should add limitations and recommendations for future studies to conclusion. They did not compare obtained results with results of other studies in this region. 

We seek to summarize the final considerations of the study to avoid being repetitive. Regarding result comparation with literature, we reviewed the manuscript and it has modified according referred by you.

We have added a subtopic (p. 15, l. 428-455) in the discussion section describing limitations and recommendations for future work. also replicated in the abstract of the article (p. 1, l. 28-30).

Furthermore, we are grateful for the practical interventions and comments on our work.