Soil Nutrient, Enzyme Activity, and Microbial Community Characteristics of E. urophylla × E. grandis Plantations in a Chronosequence

Round 1

Reviewer 1 Report

The decline in biodiversity observed in recent decades as a result of intensive agriculture and forestry is the subject of numerous research works. Particularly valuable are those that have not only great theoretical but also practical value, which includes the presented work.

Line 90, Figure 1 - please explain the abbreviations 1a, 3a, 5a in the caption under the figure, the same for Figure 2 (line 226), Figure 3 (line 264), Figure 4 (line 267)

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The study was focused on impacts due to unnatural forest plantations on soil properties including biomolecular characteristics. This study covered wide-spread planting of Eucalyptus genus, thus we can presume importance for forestry in all regions aflicted by introductory or invasive tree species. Anyway, the generalization would to be limited because of local character of the study without experimental comparison in different regions known by Eucalyptus plantation. Authors well discussed effects of the tree plantation on soil microbial communities leading to soil biodiversity loss and decomposition process negative shifts. Nevertheless, the study needs clear description of relatioships between soil physico-chemical and biological properties.

The global merit was silenced predominantly due to missing working hypothesis (research questions) in introductory section, unclear definition of statistical aims and inappropriate sentense structure in result section.

Specific comments:

Line 11: Please, use special terms only once in single sentense. So, please, reduce repetitive "Eucalyptus" from first abstract sentense to one mention. I recommend to modify formulation "...influencing Eucalyptus growth..." to more general "..influencing tree/tree-species growth...".

Line 47: What is effect of physicochemical soil properties on extracellular enzymes? As well, on soil microbial communities?

Line 64: The working thesis is missing. Here, you should explain, why did you focused on soil microbial characteristics? The specification of working thesis (or questions) should contain also definition of approaches used to answer the questions defined before.

Line 126: Please, specify by single sentense, what soil properties did you obtained?

Lines 129-132: The acronyms explaining available nutrient forms were not chosen well. We prefer chemical formulas as K⁺ for available potassium or PO₄^3- for phosphorus etc.

Line 135: The explanation toward reasons of enzymatic activity observations is necessary here. Additionally, you should to describe, why did you analysed such particular enzymes?

Lines 177-187: The whole subchapter 2.5 should contain particular aims of selected statistical procedures. There was not clear, why did you use selected statistical methods? Consequently, the processing flow was not clear. On the other hand, the use of PCoA was explained right.

Line 178: Why did you calculate alpha diversity?

Line 179: Why did use Mantel test?

Line 187: The correlation analysis was not used only among physicochemical properties, butit was used also for biochemical properties as shown at figure 6.

Line 190: This first sentense of the result section is unnecessary. Remove it, please. The mention about content in table 2 should to be moved into bracket in the end of the present second sentense.

Line 230: Please, write directly about effects of planting age and soil, and the relation with table 3 move to bracket in the end of the sentense.

The significance level p< 0.05 in relation to significant direction between compared variables is redundant in whole result section. Best, if you will present the significance level in method section.

Line 298: Discussion should contain clear statement, if you confirmed or declined your working thesis. Additionally, any sentenses containing verb "can" are uncertain, thus we prefer only clear statements under elimination of unclear formulations.

Line 329: Please, explain all acronyms in figure 6.

The English is clear and academic. I had comments only to several formulations in result section, where the authos should inform about discoveries through story, not through short mention about table content.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Interesting work, with good scientific information on the cultivation of plants of the Eucalyptus genus.

Abstract

Line 22-23: “In conclusion, the study results showed that short-term 22 successive Eucalyptus cropping exerted a significant impact on soil system”. It would be interesting to mention whether, overall, these impacts are positive or negative!

Introduction

Good

Material and Methods

Do the eucalyptus plants represent the first plantation or are they sprouts from plant stumps already installed previously? What was the soil preparation technique used to install the stands?

How did you collect the samples to evaluate the bulk density? How many samples did you collect?

Line 113-116: How many sampling points were selected in each stand? Are the 18 samples per stand or for all 3 stands? Please explain better.

Results

Line 207: “soil capacity” or soil exchange capacity?

Lines 210 and 211: “Different capital letters in the same row indicate significant differences among the different plantation ages in the same soil layer at the 0.05 level, the same below”. Capital letters?? All Tables and Figures must be read independently. Please eliminate "the same below" from the phrase and write the meaning of the letters in all Figures and Tables.

Figure 2 - Put, in de caption, the meaning of the letters at the top of the columns! Improve the presentation of Figure 2.

Line 232 and 233: “mg-kg-1”, correct this

I suggest that in columns 3 and 4 of Table 2 you replace “Microbial biomass carbon” and “Microbial biomass nitrogen” with MBC and MBN, respectively. Put the meaning of the acronyms in the title of the Table. Also include the meaning of the letters associated with the values in the title.

Increase the font size in Figures 3, 4 and 5.

Discussion

Lines 339 and 340: “The activities of urease, acid phosphatase, and invertase were high in 339 the plantations of E. urophylla × E. grandis (5a), possibly due to the high SOM in the stand”. But, younger stands have higher organic matter concentrations?? Review the sentence.

Conclusions

Good

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear authors! First, I would like to thank you for deep revision of the manuscript and respectation of all the reviewer's recommendations. In this time, I found only a few probematic points to improve manuscript, which about I would like to ask you for considering. I believe, that these current problematic points would be easy for you to input in the text:

1) Line 150: Consider use of tag "crucial". I would like to recommend alternatives such as "basic", "elementar" or "selected".

2) Subchapters 2.3 and 2.4: Please, imput relevant citations toward definitions of enzymatic activity analyses and DNA analyses. Both paragraphs lack any references except one case of microbial biomass. Unfortunately, this is insufficient.

3) Line 173: Please, remove word "Eucalyptus" from this point.

4) Subchapter 2.5: How did you explore relations between soil microbial diversity and soil chemical properties? The article need to explain reasons about common use of all used methods.

5) Lines 195-196: Please, write "Soil microbial diversity under Eucalyptus...".

6) Subchapter 3.4: Please, mention only microbial diversity in the subtitle according to definitions in sections 2.5 and 3.5.

7) Line 288: Please, prefer "microbila community" instead of "bacterial community" here to keep generalizing character.

8) Line 383. Improve subtitle 4.3 according to recommendations above.

Author Response

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Author Response File: Author Response.pdf