Regular Biochar and Bacteria-Inoculated Biochar Alter the Composition of the Microbial Community in the Soil of a Chinese Fir Plantation

Round 1

Reviewer 1 Report

It is a very interesting paper, which deals with an important subject in silviculture. Modern plant production is in constant search of environment-friendly technological solutions. Biochar is a promising method for improving soil quality and promoting plant productivity. Therefore, in my opinion, the study is on a topic of  relevance and interest to the readers of the journal.

The paper is original, clear and easy to read. Data and results are presented appropriately. The discussion is well-written and the conclusions clearly summarize the results obtained.

I have only some minor comments

L.76 What does PLFA mean?

L.151 How many soil samples were collected altogether?

1. 457 – 559 This is right….. But fungi Trichoderma and Penicillium may also affect mycorrhizal symbiosis. A high level of these fungi in soil can be harmful to ectomycorrhizal fungi.

Author Response

请参阅附件。

Author Response File: Author Response.doc

Reviewer 2 Report

The authors have tackled an interesting issue which is investigating the effects of biochar on the composition of soil microbial community in the forest which has hardly been studied. It is also clear that so much effort was put forward to conduct this research. The methodology, statistical analysis, phrasing issues and visualization of the results are very good. However, the section on discussion should definitely be improved. The discussion should be more concrete and clear. Some parts are just the repetition of the results instead of discussing the results.

There are only some minor comments:

1. Line 131: Why did you choose for these specific bacteria, e.g. Bacillus and Streptomyces to make a bacteria loaded biochar?
2. Line 148: Why did you apply the two types of biochar in the annular ditch instead of incorporating it into the soil all around the tree?
3. Please indicate in section 2.1, the exact amount of each bacterium which was added to the bamboo biochar.
4. Figures and their captions need more information. They should be self-explanatory. The abbreviations should be written in full terms in the caption of the figures.
5. Line 419: There is a recent publication on the effect of biochar and compost on soil quality in arable cropping systems which can be added to the text (D’ Hose et al., 2020, Applied Soil Ecology 156:103706, DOI: 10.1016/j.apsoil.2020.103706). They have stated “ A single application of biochar, compost and biochar-blended (BB) compost increased the C content of the topsoil in the long term, but only compost and biochar-blended compost had a lasting effect on pH and the K content. Two to 4 years after a single application of all three amendments in the field, the soil microbial biomass, richness, diversity and community composition remained unchanged.”
6. In section 4.3, the results have been repeated. However, there is no more explanation about these results or comparison with similar research.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 3 Report

I reviewed the manuscript of Liguo Song et al., on the use of biochar, with our without inoculated microorganisms. The role of biochar on the soil microbiome (bulk and rhizosphere) and growth of Chinese fir was herein assessed.

The maunscript is well written (overall) and only minor, yet important, comments need to be addressed.

 

ABSTRACT:

"Biochar is a promicsing method method ...". Revise, because biochar is not a method. Biochar is a product. A proposal of mine: "Biochar is a promising material to improve soil quality. Yet studies on biochar have mostly been carried out in laboratory conditions or have been focussing agricultural aspects."

L23-24: Revise (condense) to "The diversity of soil fungi was significantly increased, and ..."

INTRODUCTION:

L51: "However, these methods have some limitations ...". Do the authors refer to fertilizers in that sentence? If so, please write explicitely "However, the fertilizers have some limitations ...". The same reason as my first comment: a materials (either biochar, either fertilizer) is not a method.

L54: "and sustainable wayS"

L56-60: The significance of biochar, among being porous, CEC, etc. is that most nutrients (minerals AND nitrogen) from the raw biomass are largely retained in the solid biochar, after pyrolysis. The reviewer believes that these are important aspects too to include in that list in the Introduction (and discussion). You can consult/refer to e.g., https://doi.org/10.1039/D0SE00689K (among other work).

For in the discussion section: can the authors elaborate a bit more on the abiotic aspects of biochar, like: how important are the biochars' mineral and nitrogen content in ameliorating the soil? See later comments for more qpecific questions on this matter (porosity/specific surface)

L68: production of biochar (instead of creation).

METHODOLOGY

There is not so many information on biochar's physicochemical characteristics. If possible: provide some basic onformation, like elemental analysis, ash content, specific surface area, porosity. To the reviewer, knowledge on the porosity and specific surface area is important, because these are the voids/surface to which your bacteria, hyphen, etc attach.

Also, 700 °C degree is on the higher end of typical production temperatures. Can residues from Chinese fir not be used as biomass to to produe biochar? Could the authors comment on this?

Talbe 1. The caption is not very informative.

L138-139: the methodology for these techniques should perhaps be put in supplementary Information.

Results and discussion.

Table 2 is not very comprehensable.

Fig. 8: what is the significance of the dotted lines in PCA analysis?

Overall, nice work. Good luck and succes.

Author Response

Answer to Reviewer 3

Author Response File: Author Response.doc