Labile and Stable Fractions of Organic Carbon in a Soil Catena (the Central Forest Nature Reserve, Russia)
Round 1
Reviewer 1 Report (New Reviewer)
The MS investigated the labile and stable fractions of organic carbon in a soil catena. It is generally well-written. I suggest minor revision.
Fig 2 is a bit blurring.
Change Table 3 to be a figure, which should be clearer.
Any significance analysis done for the difference among samples?
Add some comparisons between the current study and published literature.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report (Previous Reviewer 3)
The manuscript has been significantly improved, and is more scientific. But I still have some a comment about soil sampling. Please actually tell the readers how many sites/pits were sampled in each location in the “Material and Methods”, and tell the readers which layer soils were sampled (since I still don’t know the 30 soil samples come from which layers and which sites, and 17 soils for carbon fractionation come from which layers and which sites). Furthermore, LINE 173, three SOC fractions (CL, CO and CS) determined in five replicates. These replicates were just for laboratory determination, it couldn’t consider as field replicates. Thus, n value in table 2 and table 3 was misleading. The author should determine the associated parameters for soil samples from the field replicates.
line 65, a comma was needed.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report (Previous Reviewer 3)
no comments.
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
Review of the ms ‘Labile and stable fractions of the… by Enchilik et al.
General comments
The authors have presented a manuscript with a potentially interesting study of soil carbon (forest floor and mineral soil) in a catena, in their case a long, forested slope with both deciduous trees and conifers. Along the slope they selected and used four plots. The authors present data for carbon of different stability, namely labile, oxidizable and stable carbon. They also made a study on litter decomposition rates at the plots. In fact, I get the impression that the litter decomposition study is a separate one and that the paper has combined two different studies that do not belong together.
The study is not well presented and needs improvement in outline and details Also the English needs to be improved as it is not clear and even causes misunderstandings. I recommend rejection.
Below I give some few detailed comments and suggestions.
Specific comments
The Introduction gives a background but I cannot see how it leads to the aims and to the litter decomposition study.
The Materials and Methods section needs more detail and a fuller description of the used methods. May I suggest that the authors subdivide the section into e.g. (i) Site description which includes latitude, longitude, altitude plus the species of the main vegetation, (ii) Sampling; depth, tools, design (iii) Chemical analysis of the sampled material, (iv) Litter decomposition experiment giving what types and species of litter that was used, how was it treated, how was it incubated and after what time intervals was it sampled. Dried at what temperature? How was the rate calculated?
Repeatedly the authors use the term ‘forest litter’ but appear to refer to ‘forest litter layer’.
Line 32. That process is not respiration. Respiration means uptake of oxygen and release of carbon dioxide
Legend figure 3 bottom line. How does ‘effervescence with 10% HCl’ fit in there?
In line 252 the authors use the term ‘decomposition rate of SOM’ and there is no reference. Did the authors actually do a study on SOM decomposition?
Lines 271 and 272 How can the authors draw that conclusion?
Reviewer 2 Report
1. The reviewer does not obtain any conclusions. The authors only list some results, and almost half of the content is about background knowledge. The abstract must be rewritten, and emphasizes the results and conclusions.
2. The introduction is divided into the many paragraphs, so the author suggested that they can be merged into the three or four paragraphs. In addition, some sentences are the poor readability, and please carefully check them.
3. The part of Materials and Methods can be simplified. It occupies the massive space of the manuscript.
4. The resolution of all figures must be significantly improved.
5. In section of experience, the reviewer does not find the information of reagent (Where did you buy it?), instrument model. Is the dry or wet samples used in the analysis in this experiment？ Please supplement it.
6. The reviewer strongly suggests that the language of manuscript should be polished due to its poor readability.
7. The discussion is not deep enough. I suggest that the discussion and the results be described separately。
8. The conclusion must be simplified and highlight important information. To «conclusion», add perspectives. Try to provide some gaps for further research; this will enhance the novelty of the paper.
Reviewer 3 Report
The study investigated the labile and stable fractions of soil organic matter along a soil catena (four different slope positions) in a mixed coniferous–deciduous forest. The study is interesting, since topography is tightly coupled with soil carbon cycling in sloping landscapes. The paper detailed introduced the organic carbon stocks and fractions in the four slope positions. But I have several comments and suggestions.
First, “Introduction” why carried out this study (just because line62 “which are currently not enough”, not enough), the introduction should be re-written and focus on your own research (such as why soil organic fractions along the soil catena is important)? also what’s the purpose of this study (line 63-65, “assess interrelationship”, not clear)? You can introduce the aims in several short sentences, and focus on what you can really support. The Introduction just introduced some knowledge associated in carbon cycling and carbon fractions. Information about how slope positions or drainage (also including vegetation type) affect carbon cycling seems important, but these were no words associated.
Second, “Material and Methods” I was confused in the sampling method and sample number. I was also confused in the similar words “forest litter”, “forest floor”, “litter”, “organic layer”, ”O horizon”, “H horizons”. I know that soil horizons were different in different slope positions, but the horizons showed in Table 1 seems different with the sampling layers. Please describe the sampling layers for each pit (each position) clearer. Line 121-128 introduce the sampling method of forest floor, how did you sample the other horizons (such as A, E horizons)? What’s the depth of A and E horizons? Which horizons are included in the “0-1.5 m layer of soil” in Figure 4?
Why forest litter had 38 samples (line 129)? forest litter from site 1 and 2 had five replicates, and no replicates for site 3 and 4? What’s the 38 samples?
Why organic carbon fractions were evaluated for 17 samples (line 134)? What’s the 17 samples?
As showed in figure 4, n=2 for each data from foot slope position (two mean samples from upper foot slope position and lower foot slope position, am I right??). while in figure 5 and Table 2, it seems that sample from upper foot slope position and lower foot slope position also had five replicates. I was confused````` If the sample number for upper foot slope and lower foot slope was one (as showed in Figure 4c), the statistical analysis would fail (no replicate) and the description about their variations (line 162-line165) was unscientific.
line 135-137, the method for organic carbon fractionation should be described more detailed.
Third, “Result”, the results about the decomposition rate of forest litter didn’t show in any table or figure.
Line 214-216, generally, the contents of TOC and CL, CO, CS would correlate with other. The correlation analysis seems unnecessary, or any special purpose??
For the analysis of soil carbon fractions, the content of each fraction was important, and the proportion of each fraction in TOC was also important. Maybe supplement a more figure or table to show their proportions in TOC, and CL% could substitute for lability indexes in table 2.
Line 230-line 232, the author should use the lability indexes rather than the CL content to indicate carbon stability. Soil/O layer in the footslope have lower lability indexes, and indicate carbon was more stable than other positions. This result was consistent with “lower decomposition rate of organic matter”.
The unit of carbon content in this paper was %, % may confuse the readers, and change the unit to mg/g dry soil would better.
The abbreviations (such as CL, CO, S, US```) in the figures and tables should be noted in the figure captions, and keep consistent. For example, CL and LC, the same meaning??
Forth, “Conclusion” line 259-260 this paper didn’t measure the organic matter migration, and the data in this paper can’t support this point. Remove
“Abstract” line 19-20, “larger stocks of organic carbon including labile fractions are restricted to the lowermost waterlogged catena positions”, this sentence was different with the results in figure 4c where TOC stocks were lowest in footslope.
