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专业: 土壤生态学

[交流] 修改意见回来了，大家看希望大不

Your paper has now been reviewed by referees and their reports are included below. The referees indicate that the paper requires considerable revisions before it can be considered further for publication.

Reviewer #1: The work is sufficiently well-written. The subject is not original and the research project is not innovative. English grammar and statistical data are sufficiently adequate. Tables and figures are clear. References are large, suitable and up-to-date.
The paper has not considered any parameters essential to quite comprehend relationships between organic matter, microrganisms and nutrients in soil such as soil respiration, light fraction, dissolved organic C and others.
The 8-year-period of different management of soil is rather short to induce clear and firm modifications in organic matter, especially for the finest fractions of soil.
The Walkley and Black (1934) is a good and fast method to determine organic C in soil, but perhaps rather imprecise and not able to differentiate values of C as very low as this study find out.
However the work can be considered a little contribution, even though partial, towards the study of the effects of different soil managements on abundance and function of soil microrganisms and enzyme activities, related with soil particle-size fractions.
I think the paper is suitable for publication exactly in this version.

Reviewer #2: This is an intersting and mostly well written paper, although the English language and spelling should be improved (ie. line 108, "soil sapling"

Due to the experimental procedures, some C fractions such as water-soluble carbohydrates are obviously missed in this study. It has been widely reported the effect of no-tillage systems on soluble C contents in soil. I would like authors to consider and discuss this topic in the paper.

Reviewer #3: General comment
The paper addresses the modification of microbial activities associated with nutrients release and SOC balance in particle-size fractions under tillage and residue management.
The subject falls within the general scope of Applied Soil Ecology and is an original contribution. The authors conducted an extensive laboratory experiment investigating the enzyme activities involved in C, N and P transformations and the nutrient contents in particle-size fractions.
I appreciate and evaluate the experimental design and the methods used are adequate for fulfilling the objectives.
The research fits the criteria for publication, but need several revisions.
In general the title, abstract, introduction and material and methods are appropriate. The results and discussion need some additional improvement.
Following listed aspects are suggested to be considered for that the article be original

Specific comments
- The manuscript presently contains about 12 text pages plus 51 references. The number of references could be reduced.

- Correct the name Kandeler (not Kandaler on P. 3)

- Give the unit of microbial biomass N (P. 7)

- No information about the loss during the fractionation procedure for the C, N, P or enzyme activities. It may be possible that these nutrient or enzymes, particularly those present in the soil solution, have been lost during fractionation process.

- In addition, considering the mass of each particle-size fraction and the C concentration (or N, P and enzyme activities) in each fraction and in the non-fractionated soil, the percentage contribution of these parameters in each size fraction to the bulk soil should be estimated and the recovery calculated.
For example calculated as ((fraction mass*C mg g-1)/(total C of bulk soil)).

- From line 180 to 186: too long for explaining the difference between the two methods. Sentence "However,...particle-size fractionation" should be deleting.

- Paragraph 4.2.: More discussion should be due. It is important also to discuss about the ecological significance of these enzymes. For example, why alkaline phosphate was studied instead of acid phosphatase?
Alkaline phosphatase in soil is thought to arise entirely from micro-organisms, while acid phosphatase is largely produced by fungi, plant, roots...

- Furthermore, there is little information on microbial biomass. There is no discussion about the microbial biomass distribution in the particle-size fraction.
Taking account the contribution of each fraction, the ecological importance of these fraction will be different.

- Interestingly, using the microbial biomass results enzyme activity : microbial biomass ratio could be calculated (as described in Landi et al. (2000) : Influence of cadmium on the metabolic quotient, L-

glutamic acid respiration ratio and enzyme activity:microbial ratio under laboratory conditions. Biol Fertil Soils 32:8-19).
An increase could be due to enrichment of the intracellular activity and in the case of enzymes also active in the extracellular environment, this may also depend on the higher extracellular enzyme activity.

- Line 235: correlation between parameters could be calculated in particle-size fractions

- Line 240: Not only enzymes, but also the organic material in clay-size fraction forms stabilized organo-mineral complexes with the clay particles and are not readily available as a nutrient source.

Discussion should be more elaborated.

Editor:
An elaboration of the discussion should also include discussion on P availability, maybe worthwhile to consult: Demetz, M., Insam, H. Phosphorus availability in a forest soil determined with a respiratory assay compared to chemical methods (1999) Geoderma 89,259-271.

[ Last edited by SHY31 on 2010-3-28 at 10:49 ]

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