Changes in Chemical and Mechanical Wood Properties in Silver Fir, Norway Spruce and Scots Pine Trees as a Result of High Temperatures Due to Fire

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article offers a concise and timely investigation into how forest fires affect the mechanical and chemical properties of key European conifer species. By analyzing fire-affected silver fir, Norway spruce, and Scots pine, the study fills an important knowledge gap created by the rising incidence of fires in regions where such events were previously rare. Its results provide useful insights for forestry management and the potential utilization of post-fire timber.

• Relevance: Addresses an important and timely topic—how increasing forest fires affect the usability of European coniferous wood.

• Strengths:

  • Comprehensive evaluation (mechanical, chemical, energetic properties).

  • Clear results showing that fire-affected wood can still be usable.

  • Practical implications for forestry and biomass utilization.

• Key Findings:

  • Slight density decrease but increased mechanical strength.

  • Higher lignin and carbon content with depth indicating carbonization.

  • Slightly higher heat of combustion improving energy potential.

• Limitations:

  • Limited detail on sampling strategy and stand variability.

  • Mechanisms behind strength increase could be discussed more deeply.

• Overall: A valuable study with practical relevance; minor methodological and interpretative clarifications would strengthen it further.

Comments on the Quality of English Language

The writing is clear, formal, and appropriate for a scientific article. The structure is logical, and technical terms are used correctly. However, some sentences are long and could be split for easier readability. Transitions between ideas are smooth, but a few sections would benefit from clearer punctuation and more concise phrasing. Overall, the style is coherent and professionally written, with only minor issues in sentence length and flow.

Author Response

Dear reviewer,

Thank you for your review. We have revised the article in terms of both language and content. It should now be easier to understand.
Our responses to your review are included in the attached file.

Best regards,
The authors

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript investigates the physical-mechanical properties and chemical composition of three coniferous wood species after fire exposure, analyzing the variation patterns in post-fire wood performance and proposing application recommendations. The findings offer valuable insights for the development of policies and standards regarding the utilization of fire-damaged wood.

Comments and Suggestions:

1) In the section describing the specimen materials, the diameter dimensions of the three wood species should be supplemented.

2)Since the wood density measured in the study refers to oven-dry density, this should be explicitly stated. It should also be clarified whether the data cited from the literature are based on comparable oven-dry density values.

3) Given the significant influence of moisture content on mechanical properties, the moisture content levels of the specimens during each mechanical test should be clearly specified. Additionally, the moisture content levels associated with any referenced literature data should be indicated.

Author Response

Dear reviewer,

Thank you for your review. We have revised the article in terms of both language and content. It should now be easier to understand.
Our responses to your review are included in the attached file.

Best regards,
The authors

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript investigates the mechanical, chemical, and energetic properties of post-fire wood from Norway spruce, Scots pine, and silver fir. The topic is timely and relevant due to the increasing occurrence of forest fires in Central Europe. The use of real fire-affected material from a recent fire event enhances the applied significance of the study.

However, several methodological and interpretative issues currently limit the scientific robustness of the conclusions. Substantial revisions are required to improve clarity, analytical justification, and contextualization.

1. Introduction

The introduction is overly long and could be streamlined to more clearly highlight the specific research gap and hypothesis being addressed.

2. Sampling Strategy and Definition of Fire Severity

Only a single fire site and a single post-fire harvest time were considered, despite the fact that post-fire degradation evolves rapidly. This restricts generalizability.

The term “fire-affected wood” is vague. There is no quantitative characterization of fire severity (e.g., time–temperature profile, charring depth, location relative to burn scars).

Mechanical testing was performed only on material close to the surface, which likely overrepresents the thermally densified layer and does not reflect the bulk behavior of affected timber.

A more detailed description of fire conditions and sampling depth is necessary to validate the representativeness of the specimens.

3. Mechanical Properties

While increases in bending and compressive strength compared to literature values are reported, the discussion does not sufficiently acknowledge:

1. the increased brittleness typically associated with thermal exposure,
2. potential earlywood collapse influencing small-specimen performance,
3. that literature reference values represent broad natural variability and not true controls.

Implications for structural use should therefore be moderated or supported by additional data such as modulus of elasticity, toughness, or fracture behavior.

4. Chemical Analysis

Table 3 reports a lignin content of ~66% for silver fir bark, which is unrealistically high for conifers and likely reflects analytical or reporting errors or bark/wood misclassification. These results must be verified before drawing conclusions regarding chemical stability.

5. Statistical Analysis

Although means and standard deviations are provided, there is no indication of statistical significance between groups. Appropriate hypothesis-based statistical testing (e.g., ANOVA with post-hoc analysis) is required to support claims regarding changes in mechanical or chemical properties.

6. Conclusions

Some statements overstate the applicability of the material for construction (“remains in compliance with standards”, “high industrial value”), despite the lack of durability, ductility, and dynamic-loading assessments. The conclusions should be revised to align with the limitations of the presented data.

 

Author Response

Dear reviewer,

Thank you for your review. We have revised the article in terms of both language and content. It should now be easier to understand.
Our responses to your review are included in the attached file.

Best regards,
The authors

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The revised manuscript shows a clear improvement compared to the previous version. The authors have adequately addressed the major reviewer comments by clarifying the sampling strategy, defining fire severity and sampling depth, correcting the chemical composition data, and substantially improving the discussion of mechanical properties. The conclusions have been revised appropriately and no longer overstate the structural applicability of fire-affected wood.

Although inferential statistical analysis was not included, the limitation is now clearly acknowledged and the interpretation of results remains cautious and transparent. Overall, the revisions have significantly strengthened the scientific clarity and balance of the manuscript.