Sight versus Sound: Do Visual Assessments of Dead Standing Trees Reflect Acoustic Nondestructive Evaluations of Wood Quality?
Round 1
Reviewer 1 Report
Manuscript ID:forests-1945946
Title:Sight Versus Sound: Do Visual Assessments of Dead Standing Trees Reflect Acoustic Nondestructive Evaluations of Wood Quality?
Authors:Tyler J Hovde , John W Forsman , Robert J Ross , Mark Rudnick , Xinfeng Xie , Xiping Wang * , Yvette L Dickson *
1.Overall Recommendation
Accept after Minor Revisions
2.Brief Summary
The efficient use of wood helps to increase its value. The objective of the authors' study was to explore techniques for effective classification of white spruce following an outbreak of spruce budworm for efficient use of the wood. Assessing the quality of wood with visual identification is less accurate, so the authors divided the trees into three categories and then examined them separately in both longitudinal and transverse acoustic nondestructive tests. It was found that visual appearance was only roughly correlated with wood quality and that longitudinal acoustic velocity was a good indicator of wood modulus of elasticity. This manuscript is well written, clear and concise and I can only give minor suggestions for improvement.
3.General Concept Comments
The authors classified 149 mature white spruce into three categories, i. e., category 1 (live trees with visible green foliage), 2 (dead- standing trees with no visible green foliage, recently dead), and 3 (dead-standing trees with poorest visual appearance, obvious signs of severe decay), by visual characteristics of decline and decay. Is there a corresponding theoretical support for such a classification method? Do the detailed characteristics corresponding to each category reflect the quality of the wood? And the details referenced by the classification criteria are not clearly identified through Figure 1, which needs to be supplemented.
The authors point out that the longitudinal acoustic velocity is the highest in the third category and the lowest in the first category of trees at a constant moisture content. It is also pointed out that the quality of wood with higher acoustic velocity is higher than that of wood with lower acoustic velocity, and these two statements are clearly in conflict with each other. Is it possible that the highest longitudinal acoustic velocity of the third group of trees is caused by the reduction of wood density due to internal decay? I would like to ask the author to provide clarification on the mentioned content.
The purpose of this study is to state a technique that can effectively classify white spruce. The authors eventually used visual assessment to identify category I and category III and further classification of category II by acoustic nondestructive tests to achieve efficient use of wood, but the specific method for further classification of category II with acoustic nondestructive tests is not detailed and needs to be supplemented.
4.Specific Comments
1) Lines 148-149: Some figures are needed to show the detailed features of the trees in category II.
2) Lines 159-160: Some figures are needed to show the detailed features of the trees in category Ⅲ.
3) Lines 166-167: How to evaluate the quality of wood by acoustic velocity?
4) Lines 169-171: Is there a theoretical support for such test method? Does the measurement of the quality of the wood at this height enough to represent the quality of the wood of the whole tree?
5) Lines 239-240: Does the decrease in acoustic velocity simply result in lower tree moisture content?
6) Lines 259-260: Is there any theoretical support for such a statement?
Author Response
3.General Concept Comments
The authors classified 149 mature white spruce into three categories, i. e., category 1 (live trees with visible green foliage), 2 (dead- standing trees with no visible green foliage, recently dead), and 3 (dead-standing trees with poorest visual appearance, obvious signs of severe decay), by visual characteristics of decline and decay. Is there a corresponding theoretical support for such a classification method?
Response: There is no standard visual grading criteria for dead trees. We defined visual categories referencing the US Forest Service Inventory and Analysis (FIA) data collection protocols. See Line 55-60 in Introduction.
Do the detailed characteristics corresponding to each category reflect the quality of the wood?
Response: This is part of the questions we tried to answer in this study.
And the details referenced by the classification criteria are not clearly identified through Figure 1, which needs to be supplemented.
Response: unfortunately, we do not have closeup photos that can show the detailed features.
The authors point out that the longitudinal acoustic velocity is the highest in the third category and the lowest in the first category of trees at a constant moisture content. It is also pointed out that the quality of wood with higher acoustic velocity is higher than that of wood with lower acoustic velocity, and these two statements are clearly in conflict with each other. Is it possible that the highest longitudinal acoustic velocity of the third group of trees is caused by the reduction of wood density due to internal decay? I would like to ask the author to provide clarification on the mentioned content.
Response: This is discussed in the text Line 259-270.
"In general, higher longitudinal velocities indicate better wood quality than lower velocity. Holding moisture content constant, the lower quality trees of category 2 and 3 have a higher longitudinal velocity than category 1. This discrepency is largely caused by the reduced moisture content in category 2 and 3. In this study, the measured moisture content of each wood sample is an average value for the disk. Fig. 4 indicates about 10% decrease in moisture content for category 2 and 3 comparing with category 1. Assuming same wood quality among 3 categories, just considering the effect of moisture content, then the longitudinal acoustic velocity is expected to increase for category 2 and 3. In addition, the dead-standing trees in category 2 and 3 might have a moisture content gradient in radial direction as a result of natual drying postmortem, drier outerwood and wet corewood. The increased acoustic velocity in category 2 and 3 is most likely the result of the drier outerwood, which can overshadow the effect of wood deterioration."
The purpose of this study is to state a technique that can effectively classify white spruce. The authors eventually used visual assessment to identify category I and category III and further classification of category II by acoustic nondestructive tests to achieve efficient use of wood, but the specific method for further classification of category II with acoustic nondestructive tests is not detailed and needs to be supplemented.
Response: "This study was the first attempt to assess wood quality of dead standing trees using acoustic techniques. Further investigation is needed to fully address the some of the challenges we are facing. "
4.Specific Comments
1) Lines 148-149: Some figures are needed to show the detailed features of the trees in category II.
"Unfortunately, we do not have closeup photos that show detailed features of the trees in category II. But we have detailed descriptions in the text."
2) Lines 159-160: Some figures are needed to show the detailed features of the trees in category Ⅲ.
"Unfortunately, we do not have closeup photos that show detailed features of the trees in category III. But we have detailed descriptions in the text."
3) Lines 166-167: How to evaluate the quality of wood by acoustic velocity?
"This is well documented in literature. See text in Line 77 - 89".
4) Lines 169-171: Is there a theoretical support for such test method? Does the measurement of the quality of the wood at this height enough to represent the quality of the wood of the whole tree?
"This is well documented in literature. See text in Line 67 - 76".
5) Lines 239-240: Does the decrease in acoustic velocity simply result in lower tree moisture content?
No. Lower tree moisture content should result in higher acoustic velocity.
6) Lines 259-260: Is there any theoretical support for such a statement?
"Yes, this is a well known fact documented in many literatures. for example reference #13 ".
Reviewer 2 Report
Review of article for the journal Forests - MDPI
Manuscript Number: forests-1945946
Article submitted: 23 September 2022 (12 p.)
Title of the manuscript (Article):
Sight Versus Sound: Do Visual Assessments of Dead Standing Trees Reflect Acoustic Nondestructive Evaluations of Wood Quality?
Authors:
Hovde, T.J., Forsman, J., Ross, R.J., Rudnick, M., Xie, X., Wang, X., Dick-son, Y.L.
________________________________________
The manuscript deals about an interesting issue of forest companies, i.e., how to the best (quickly and without increased financials) evaluate wood quality of dead standing trees directly in forests. Its results are based on a representative amount of the standing white spruce trees (together 149, i.e., in 1st category 50 live with green foliage; in 2nd category 49 dead-standing without visible foliage; in 3rd category 50 dead-standing with large absent of needle bearing branches).
It is well written and will be interesting for experts in the field of forestry, logging and wood processing.
I have these comments and recommendations.
1. Introduction
- Lines 107-109: This sentence should be in chapter 2, at which it was there partly repeated.
2. Materials and Methods
- Line 188: Figure 2a should be Figure 2 (see line 171), and Figure 2b should be Figure 3 (see line 175).
-
Results
- The highest problem at using the acoustic methods in forests is a fact that their results are influenced not only by wood quality (rots, insect galleries, etc.) but also by moisture content of wood in the individual parts of live and dead trees (e.g., sap and heart). Therefore achieved results are not totally representative.
- Why there were not calculated the dynamic MOE from the longitudinal acoustic velocities and wood densities?
- How can be explained the fact in Figure 6, that for wood in live trees was at a given moisture content (e.g. 60%) the wave velocity lower comparing with wood in partly or totally dead trees having a higher potential of lower quality (rot, etc.) ?
-
Discussion
- Lines 312-313: In the sentence should be opposite formulations, i.e. The transverse acoustic velocity … did not significantly explain categories of trees quality from 1 to 3 given by visual analyses.
Finally, I can recommend the manuscript after minor revisions for publication in the Forests MDPI journal.
27 September 2022 Reviewer
Author Response
- Introduction
- Lines 107-109: This sentence should be in chapter 2, at which it was there partly repeated.
Response: Corrected.
- Materials and Methods
- Line 188: Figure 2a should be Figure 2 (see line 171), and Figure 2b should be Figure 3 (see line 175).
Response: Corrected.
- Results
- The highest problem at using the acoustic methods in forests is a fact that their results are influenced not only by wood quality (rots, insect galleries, etc.) but also by moisture content of wood in the individual parts of live and dead trees (e.g., sap and heart). Therefore achieved results are not totally representative.
Response: Agree. Further investigation is needed.
Why there were not calculated the dynamic MOE from the longitudinal acoustic velocities and wood densities?
Response: 1) Wood density of the trees is unknown. 2) We were looking for a simple approach for assessing wood quality of standing dead trees, not predicting wood properties.
- How can be explained the fact in Figure 6, that for wood in live trees was at a given moisture content (e.g. 60%) the wave velocity lower comparing with wood in partly or totally dead trees having a higher potential of lower quality (rot, etc.) ?
Response: This is discussed in the text of line 259 - 270.
4. Discussion
- Lines 312-313: In the sentence should be opposite formulations, i.e. The transverse acoustic velocity … did not significantly explain categories of trees quality from 1 to 3 given by visual analyses.
Response: Maybe. Here the visual appearance is compared against transverse acoustic measurement.
Reviewer 3 Report
density sapwood / heartwood?
MC sapwood / heartwood
density=f(MC)
MOE =f(density, TOF)
picture 5: explain the meaning of the symbols a and b
maybe NDT methods should be used not in the forest, but before their further processing?
Author Response
picture 5: explain the meaning of the symbols a and b
Response: symbols "a", "b", and "a, b" have been removed in Figure 5.
maybe NDT methods should be used not in the forest, but before their further processing?
Response: In the same study, NDE methods were used to evaluate wood quality of the logs and lumber obtained from the harvest tree samples. The results are reported in a Master's Thesis by Tylor.
