Carbon and Nitrogen Stable Isotope Abundance and Soil Stoichiometry of Zanthoxylum planispinum var. dintanensis Plantations of Different Ages
Round 1
Reviewer 1 Report
Dear authors,
Your paper on carbon and nitrogen stable isotope abundance and soil stoichiometry of Zanthoxylum planispinum var. dintanensis plantations of different ages is very interesting and provides new data, however there are some issues, particularly related to sampling and analysis that have to be improved before acceptance of the manuscript. Hope the suggestions will help to improve the MS.
Detail comments:
- In the Introduction part is missing basic information about the plant metabolism and isotope fractionation in C3, C4, CAM plants (e.g. (Hoefs, 1997) and the importance of C/N ratio data in evaluation of organic matter degradation. Also the C and N cycles including the main C and N sources should be discussed more. E.g. CO2 concentration and isotope composition are changing in time and space and can therefore influence the plant composition. In karst areas, carbonate dissolution also plays an important role and influences the isotope composition of the dissolved inorganic carbon as important nutrient source for plants. Also the sources of nitrogen can change in space and time considerably. Add more information about the selected plant; suggest adding figure with plants of the 4 different forest ages to see the visual difference.
- In the Materials and methods, add figure of the location and schematic presentation of sampling design.
- Line 113: you mean probably Table 1 (not 99)?
- Paragraph 2.2.2: Sample preparation is different for leaves, litter and soil. Did you follow some recommended protocols? How did you avoid degradation of organic matter and fractionation of C and N in samples? For how long was the soil dried, at what conditions to prevent the fractionation?
- Paragraph 2.2.3: It is not clearly described how the analyses were performed. In carbonate terrains, the carbonate dust/rocks influence the bulk C elemental and isotope composition. How was assured that carbonate fraction did not influence your elemental and isotope composition? Were C and N analysis performed simultaneously? If carbonate is present it should be removed (e.g. with HCl) from samples prior to C analysis and N should be measured separately as acidification can cause huge fractionation.
- Paragraph 2.2.4: include in data evaluation also calculation of the Corg/N ratio.
- Results: All results should be included in Supplementary or in some other accessible data repository. Add in MS the summary table with basic statistics for each group of samples and refer in text appropriately. Check all combinations, correlations listed carefully again. E.g. leaf litter d13C is correlated with litter C; leaf d13C is significantly correlated only with leaf N (not leaf litter d15N). Suggest only significant correlations to be discussed.
- Discussion: On many places, it is not clear about which data authors discus. E.g. line 203 d13C of what? Line 238 the average variation d13C of what? In lines 236, 238 you probably mean ‰ (not %).
- Line 239: “… indicating that the vegetation in this area changed substantially.” – What is the possible reason? Did the vegetation type or atmospheric CO2 isotope composition change?
- Line 250: According to soil characteristics the on karst areas it is hard to apply universal sampling. It is more important to distinguish among different soil layers (e.g. O, A, B, C horizons) in which the % of organic matter changes considerably. In B and C horizons carbonate contribution can influence the isotope composition considerably if the carbonate fraction is not removed. Therefore, analytical part plays very important part for further discussion on results.
- Line 280: In paragraph 4.2 authors discus C/N ratios but as exposed before nothing is explained about this parameter in introduction and methods paragraphs.
- Lines 309-310: Check the expression d12C and d13C in this sentence. You probably mean 12C and 13C isotopes?
- Funding and Supplementary data is missing
- Figure 1: suggest to present with box plots. Is not clear what a, b, ab, c, bc stand for? For concentrations you can use logarithmic scale.
- Figure 3: What do read and black arrows stand for?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
In the manuscript the authors relate C, N and their isotope as well as soil stoichiometry to understand the mechanisms which could explain the soil quality index. The manuscript is well written, the methodology followed for sampling, collection and processing of data is well explained and the results are consistent and statistically supported.
I have minor suggestion to improve the manuscript.
- It was not possible to corroborate all references as most of the are in Chinese. I suggest to support statements by references in English.
- In page 3 line 113, correct (Table 99) for (Table 1).
- In page 4 lines 159–173, to make statements more clear I suggest to refer each sentence to the proper plot. Furthermore, I suggest to label plots in Figure 1 as 1a, 1b, 1c and 1d.
- In lines 160–161, I suggest to remove the phrase "which may indicate that water..." as it is explained in the context of the discussion.
- Line 189, I suggest to order the tables as they appear in the main text.
- Line 193, correct "MBC" for "MCN".
- Page 5 line 194, correct "leaf C" for "leaf δ13C"
- Line 196 correct "was small" for "were small".
- Line 211. The authors state that their results are consistent with Kieckbusch et al. (2004) results but inconsistent with Lee et al (2000) conclusions. Can the authors explain in more detail these differences?
- In page 11 Fig 3, I suggest not to use arrow for both objects and variables.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors,
Please add in paragraph 2.2.3 the detail explanation about methods performed with relevant references mentioned in the respond to review.
Add also numerical data in Supplementary material.
Author Response
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Author Response File: Author Response.pdf
