Effects of Mixing Feldspathic Sandstone and Sand on Soil Microbial Biomass and Extracellular Enzyme Activities—A Case Study in Mu Us Sandy Land in China
Round 1
Reviewer 1 Report
This study reports the effects of adding feldspathic sandstone soil to a sand soil on physical properties of the sand soil and enzymatic activities. The main findings were that there was greater soil microbial mass and enzymatic activities in the mixed soil vs. sand soil. P was relatively more limiting in the mix than in the sand. These results are suggested to be evidence that adding feldspathic sandstone to areas characterized by the sand soil will improve their ability to support plant growth.
There are two major shortcomings of this study. 1) One of them is that the sandy soil and the soil mixture were measured but feldspathic sandstone never was measured. So, this makes it very difficult to infer causation of anything. It is possible that every pattern found here is simply an average or intermediate property of the two base soil types. If I missed these sandstone data, please direct the reader to them. If you have collected the data but do not include them, please include them. But, if they have not been collected, the discussion should include as a likely explanation that the mixed soil is simply intermediate between the san d and sandstone soils. 2) The other issue is the time scale of this study. If I am reading it correctly, two soils were collected. One of them was immediately measured [sand]. The two soils were mixed together and this mixture was immediately measured. How does this properly reflect land remediation? It seems that everything here is simply an averaging of two soil types [which as I mention above cannot be properly assessed] and all of the important things that represent remediation [such as changes in types and amounts of microbes, changes in soil nutrient cycling, changes in nutrient retention] are left out. So, please clarify how long sandstone and sand were mixed together – I hope I am wrong and measurements were not made on soils that had just been mixed. If they were in fact just mixed, then the discussion needs to include this shortcoming (that most of the processes of land remediation could not be assessed). If measurements were shortly after mixing, everywhere that the discussion (or other places) refers to “before and after land remediation” should be changed to “in sand vs. a mix of sand and sandstone”. The title should also become something like “Effects of mixing sand and sandstone on …”
Quality of writing is good. Use of the literature is strong. Quantitative methods are appropriate.
The discussion is much too long and too speculative. The existing discussion could be reduced to 1/3 of its length.
I do not understand the experimental design – please explain what was done at the scale of a plot. Right now it sounds like they are simply different local areas in which soil was collected and brought back to the lab.
Be consistent in name of land type – Make it either “Sand Land” or “Sandy Land” but don’t switch back and forth
In the abstract it says “effects on” for things that are correlations. Rephrase to something that reflects correlations.
In the abstract define all abbreviations at first usage. Define each abbreviation again at first usage in the main text.
The dual y-axes in figures 1a and 2a are very confusing. Please redo these figures.
What is N (sample size) for Fig 3?
What is N (sample size) for table 4?
Line 323 (and others) – where are the data on aeration and permeability? Did I miss them? If not, remove from discussion.
Author Response
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Author Response.pdf
Reviewer 2 Report
This paper describes an in depth study of microbial and other soil parameters comparing soil after remediation and control, although I am not able to understand the details of what has been done. The main problem is that it needs to be explained more clearly what the two treatments are. The way it is written now, it sounds like they only sampled soil and mixed some other material into part of it after sampling. This cannot be right?
I also think the paper has a lot of detail, but does not give much understanding. It may not be possible to get so much more understanding out of it, but I urge the authors to try.
Minor comments
Abstracts: too long, try not to use so many abreviations.
Introduction. The land remediation should be better explained, what is the role of it?
Material and methods: as mentioned explain what the treatments are. Also give more details about the remediation treatment.
Vector length and angle: This analysis method is not known to me, I would have like more explanation.
Results: OK, many results, is it possible to summarise more?
Discussion: Mostly OK, but long, difficult to follow. Only in conclusions is it mentioned anything about soil fertility, should maybe discuss the impact of the various parameters more. “Om the other hand” is used a lot even when I cannot see any obvious contradiction. Line 459 ends unfinished.
Author Response
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Reviewer 3 Report
Interesting paper describing a case-study of soil development after soil land reclamation. Interesting contribution to understanding of the remediation processes.
However I have a few comments / issues to be resolved prior to publication:
The term "remediation" is from latin "remedio" = to cure. This implies that the land is "ill". I did not understood from the text, whether the desertification is a natural state or man-induce. Maybe the term "reclamation" could be better? The studied remediation / reclamation is not well described in the text. I think this requires more detils. You determined many soil parameters but not water-holding capacity. This is a parameter extremely important for improvement of desert-like sandy soils. Authors use a series of abbreviations of enzymes, soil microbial nutrients, soil nutrients etc. These are not defined in the first appearance (including abstract!). I would propose to make a list of abbreviations. Line 41. You claim that "such changes were mainly modulated by SWC and SOC". I did not get the feeling that this claim is fully proved by the data. I think this shall be better explained.Line 47. I do not think that desertification is a problem of "most countries". LIne 60 "Chen et al. [9] believed" - I think there might be a better workd, such as "proved" or "suggested". Believe is a matter of religion, not science. Line 119 - use upper index for km2. Lines 168-173: The desfription of principal of the enzyme determination is very unclear. I would propose to make it shorter and clearer. The principal is clear - the enzymes hydrolyze the artificial substrates and produce MUB, which could be determined by fluorescence. Line 178 - please explain in more details the blank. Was is it just water or water extract without the fluorescent marker? You used parametrical statistics (ANOVA, Pearson correlation). These however require the normality of the data. Did you tested this normality? You have calculated the redundancy analyses but you do not discuss its reults very much. Tables 2 and 3. Please add number of replicates to the table caption (n=...). Secion 4.2. - It would be interesting to have the ANOVA results (table?) here. line 341 - use "microbes" instead of "microbial" Lines 397-400. This sentence is very difficult to understand. Line 443 - the words "proved" and "might have" do not go together; "proved" implicates that you 100% sure while "migh have" indicates large uncertainty. Lines 453-455. The litter input is not the only input of organics from plants into soil. Root exudation plays important (often more important) role. Line 459: "prove" - Are you sure? If not, I would propose to use "support our hypothesis". Line 480: use singular not plural of "grants" (there is only one number".Author Response
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Round 2
Reviewer 1 Report
The authors have done an excellent job of addressing my concerns (I was reviewer #1). The addition of details about the time of soil placement in the field was the most critical addition.
Author Response
GENERAL COMMENTS: The authors have done an excellent job of addressing my concerns (I was reviewer #1). The addition of details about the time of soil placement in the field was the most critical addition.
Response: We greatly appreciate your positive comments.
Reviewer 2 Report
The manuscript is much improved, but there are still some issues, and a number of mistakes on spelling and choice of words.
For example:
L 22 Monitored – use e.g. “investigated”. It should also be stated over how long time, it is not very long.
L 27 Estimated – use “measured”
L 41-42 A bit too ambitious?
L 48 Rephrase and explain better
L 65 What is meant by “unbalanced nutrients”?
L 85-92 shorten, it is not clear where this is going.
L 98-99 What does this mean? “…independently contains feldspatic sandstone and sand.”
L 1321-135 I cannot understand this.
Section 2.1 Make it clearer how these soil types are naturally distributed, if necessary use a map.
Section 2.2 It has become clearer how this was done. Should stress more exactly how long the mixed soil was incubated (only a few months). What is “experimental base”?
Description of vector length and vector angles have become clearer, but the reason why they were used should be in materials and methods and certainly not in conclusions. I also wonder if not CANOCO that was also used could do something similar (e.g. PCA).
Discussion is improved. Should stress that these changes happened after an incubation of the mixed soil of only a few months. Many sentences are unfinished, check for that. Also try to avoid value loaded words.
The discussion about microbial biomass sounds confused. The soil habitat was “negative” on one hand, but on the other hand “promoted microbial reproduction”. I also wonder how the comparison with forest soil was done. Forest soil is often organic and light, so microbial biomass on weight basis will be low.
L 369-430 and 439-445 I cannot understand this. The statement in the the points to supporting a hypothesis, but I don’t know which?
Author Response
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Reviewer 3 Report
The authors did very good job revising the manuscript. I have only a few minor comments and recommendations:
Table 2,3 - please also indicate what values after +- mean i.e. means+-std. deviation, n=3). I do not agree that determination of WHC is a long-term procedure. It is a standard procedure carried out by many laboratories on routine basis. Response 9. - In the new sentence there is "determination" missing (i.e. Briefly, the principle of enzyme activity DETERMINATION is the ....". Response 11. The normality test should be mentioned in section 2.5. The table can be placed into Supplementary. Response 16. I would propose to split the new sentence (make "It may also related...") separately. English does not use such long sentences.Author Response
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