Benefits and Limitations of Winch-Assist Technology for Skidding Operations
Round 1
Reviewer 1 Report
This paper deals with the contents of cable-assist harvesting, which has recently been widely used on harvest sites. In particular, it is regarded as a thesis logically verified using data from field experiments to consider the advantages and limitations of the cable assistant method for scooter operation, which has not been dealt with much. The methodological approach is logical and correct. It is thought to be a useful paper for many readers in time. And I also hope that this paper will be used to evaluate the cost-effectiveness of winch-assisted skidding operations in the field.
The followings are some questions and suggestions.
If possible, I would like Figure 1 to be replaced with a photo that expresses the winch-assist harvest system well to help readers understand.
In Table 2 and Table 5, it seems that the mean values and grouping for each trail of load volume are different(trail A), but why is this difference?
It is recommended to express the soil texture and moisture content of each trail in the paper.
Is there any conclusion?
Need to state conclusions supported by the results
Author Response
Reviewer 1
COMMENT 1: This paper deals with the contents of cable-assist harvesting, which has recently been widely used on harvest sites. In particular, it is regarded as a thesis logically verified using data from field experiments to consider the advantages and limitations of the cable assistant method for scooter operation, which has not been dealt with much. The methodological approach is logical and correct. It is thought to be a useful paper for many readers in time. And I also hope that this paper will be used to evaluate the cost-effectiveness of winch-assisted skidding operations in the field.
RESPONSE 1: Thank you very much for your favourable evaluation of our study, and for the encouragement: that does help keeping strong our motivation ?
COMMENT 2: The followings are some questions and suggestions.
RESPONSE 2: Thank you very much for your helpful suggestions and comments.
COMMENT 3: If possible, I would like Figure 1 to be replaced with a photo that expresses the winch-assist harvest system well to help readers understand.
RESPONSE 3: We acknowledge that Figure 1 is a bit congested and may be somewhat confusing. However, we do not have a better picture containing both the skidder and the winch. That picture also has the merit of including the tracked loader tasked with preparing the loads for the skidder. It was very difficult to capture all three machines in the same frame, but we were lucky enough and were offered a good photo opportunity. The price for comprehensiveness was congestion, which makes the picture somewhat difficult to decipher, as the Reviewer rightly says. As a compromise solution, we propose the same figure, where this time we have clearly highlighted and marked the different components of the operation. We have also revised the figure caption to make it easier for the reader to decipher the scene. We hope that after those revisions the figure is easier to understand.
COMMENT 4: In Table 2 and Table 5, it seems that the mean values and grouping for each trail of load volume are different (trail A), but why is this difference?
RESPONSE 4: We apologize for that. The difference was for Treatment Winch assist + Moderate Slope and it was due to rounding to one decimal figure. We have checked the data and restored consistency with the rounding.
COMMENT 5: It is recommended to express the soil texture and moisture content of each trail in the paper.
RESPONSE 5: We did not collect that information. However, we have introduced a description of the soil type in the revised manuscript version. We acknowledge that soil texture and moisture content have a strong role in determining soil sensitivity to traffic-induced damage. However, to the purpose of our study, such information is not indispensable (although it would have been desirable). Our study is comparative in its goals and nature: therefore, it is invalidated only if conditions differ between the treatments that are being compared. That was not the case of either texture or soil moisture content, given that soil type was the same and that soil and weather conditions remained the same all along the duration of the study, so that it was very unlikely that soil got wetter or dryer in the time elapsed between the application of one treatment and that of the other one.
COMMENT 6: Is there any conclusion? Need to state conclusions supported by the results
RESPONSE 6: We have added a Conclusion section as recommended.
Reviewer 2 Report
Benefits and Limitations of Winch-Assist Technology for Skidding Equipment
General:
The paper should be presented as an observational case study.
The soil disturbance component of the paper comes across as an “add-on” and is not directly related to the subject matter as described in the title. It should not be included in the paper. If you keep it, it should be limited to the interaction of the skidder with soil disturbance on skid trails as well as the interaction of winch assist or not. Otherwise, soil disturbance should be a separate paper.
With respect to the winch-assist analysis, the authors need to clearly identify which variables are independent and dependent. There is also no mention that the "winch" is a dummy variable.
To avoid confusion in tables and figures, please include the full forms of abbreviations (e.g., SS, Eta in Table 4, WA in Figure 2). It would be easier for readers to follow.
Generally, all table and figure captions should be more descriptive. They need to stand alone without support for the main text.
Specific comments:
L23 – also known as “tether logging”
L75 – make it clear to reader that you are referring to a grapple skidder
L90 – soil disturbance objective does not fit with the introduction; it is evident that this analysis is not limited to the skidder
L94 – specify whether it was a clearcut
L134 – soil type needs to be described
L151- provide map of study area showing skid trails and location of soil transects
L169 – stems small or large? Provide stem diameter thresholds
L171 – clarify what smaller vs larger stem diameters means; did you have mixed sizes within bunches?
L177 – need background on soil moisture
L178 – manuscript title implies skidder only, but now it appears that the soil component is across the entire harvest area – this is confusing
185 – soil survey classifications in table 1 do not address soil compaction;
not clear how depth of rutting was measured; the degree of rutting is influenced by soil moisture, but soil moisture was not measured.
Why would you expect soil disturbance when there is logging slash?
Was slash distributed over skid trails as a BMP?
Table 7 is confusing. It provides percentages for before and after skidding, yet the measurements were not limited to skid trails, but rather the entire harvest area.
Generally, the soil component of this paper is confusing and does not fit well. It should be another paper.
When reporting the results of the GLM model, please add coefficient estimates (with the positive/negative sign) and standard errors for each variable in Tables 4 and 6. In addition, the Error DF and the SS need to be explained.
L219 – how was load size monitored? Did the skidder operator have discretion to increase load size with winch-assist versus without? Or was load size pre-determined by the shovel operator setting up bunches?
L245 – using winch always resulted in larger load size; again, was this a judgement call on the part of skidder operator?
L261 – the fine-tuning of load size needs more explanation
L267 – Figure 2 – counter-intuitive that “steep wa” would have the lowest productivity; the higher payloads should compensate for longer skid times
L295 – I could not find figure 3. Figure 4 is not referenced in the text. The figure 4 caption needs to be more descriptive. Make it clear that the x-axis represents one hour.
L372 – this study does not assess cost-effectiveness
L388 – the role of the skidder operator is critical to results; setting tension is one variable, but also need to discuss load size;
L395 – perhaps the skidder operator was too conservative with load size decision with winch assist
Author Response
Reviewer 2
COMMENT 1: The paper should be presented as an observational case study.
RESPONSE 1: I am not sure about that. We did manipulate treatments and got the driver to switch between trails according to a specific experimental plan, so this was not properly an observational study where the researchers simply record what is going on without interfering with the phenomenon being observed. We did interfere. Obviously, there was only so much we could get the contractors to do, and if the winch was down for some time we could not ask the whole operation to pause as we waited for the winch to be repaired. So – yes – we had to adapt the experimental plan to circumstances, but there was a precise experimental plan and it was followed as much as possible by all involved parties.
COMMENT 2: The soil disturbance component of the paper comes across as an “add-on” and is not directly related to the subject matter as described in the title. It should not be included in the paper. If you keep it, it should be limited to the interaction of the skidder with soil disturbance on skid trails as well as the interaction of winch assist or not. Otherwise, soil disturbance should be a separate paper.
RESPONSE 2: We respectfully disagree: We explicitly stated that “The goal of this study is to contribute to our knowledge of winch-assist skidding, as used in a typical plantation forestry site with moderate to steep terrain. In particular, the study aimed at determining the impact of winch-assistance on 1) productivity and 2) soil disturbance”. Therefore, soil disturbance is indeed a component of the study, and in the Introduction section we have explained why it should be included in any assessment of winch assist technology. For that reason, we believe that its inclusion in the study is fully legitimate.
COMMENT 3: With respect to the winch-assist analysis, the authors need to clearly identify which variables are independent and dependent. There is also no mention that the "winch" is a dummy variable.
RESPONSE 3: We have introduced a further description of which variables were dependent and which were independent. We have also provided a more extensive description of model formulation and data analysis.
COMMENT 4: To avoid confusion in tables and figures, please include the full forms of abbreviations (e.g., SS, Eta in Table 4, WA in Figure 2). It would be easier for readers to follow.
RESPONSE 4: We have indicated the full forms of abbreviations, as suggested.
COMMENT 5: Generally, all table and figure captions should be more descriptive. They need to stand alone without support for the main text.
RESPONSE 5: We have introduced more details in the Table and Figure captions and notes, as suggested.
COMMENT 6: L23 – also known as “tether logging”
RESPONSE 6: Of course. However, tethered logging is a term that is used mostly in the US West Coast, especially in the past.
COMMENT 7: L75 – make it clear to reader that you are referring to a grapple skidder
RESPONSE 7: Edited as suggested.
COMMENT 8: L90 – soil disturbance objective does not fit with the introduction; it is evident that this analysis is not limited to the skidder
RESPONSE 8: We respectfully disagree: We explicitly stated that “The goal of this study is to contribute to our knowledge of winch-assist skidding, as used in a typical plantation forestry site with moderate to steep terrain. In particular, the study aimed at determining the impact of winch-assistance on 1) productivity and 2) soil disturbance”. Therefore, soil disturbance is indeed a component of the study, and in the Introduction section we have explained why it should be included in any assessment of winch assist technology. For that reason, we believe that its inclusion in the study is fully legitimate.
COMMENT 9: L94 – specify whether it was a clearcut
RESPONSE 9: We have introduced this information, as suggested.
COMMENT 10: L134 – soil type needs to be described
RESPONSE 10: Good idea. We have introduced a better description of the soil type encountered at the study sites. However, we have introduced the new description earlier on in the text, where the experimental site description is reported. We think that information belongs there and we hope you agree.
COMMENT 11: L151- provide map of study area showing skid trails and location of soil transects
RESPONSE 11: We have introduced the map, showing the position of the landing, the skidding trails and the transects. Obviously, we have re-numbered all figures accordingly.
COMMENT 12: L169 – stems small or large? Provide stem diameter thresholds
RESPONSE 12: We have the volume figures – not the diameter figures – and we have introduced that information to the revised manuscript version, as suggested.
COMMENT 13: L171 – clarify what smaller vs larger stem diameters means; did you have mixed sizes within bunches?
RESPONSE 13: Yes, we did.
COMMENT 14: L177 – need background on soil moisture
RESPONSE 14: Unfortunately, we did not record that information. We acknowledge that soil moisture content has a strong role in determining soil sensitivity to traffic-induced damage. However, to the purpose of our study, such information is not indispensable (although it would have been desirable). Our study is comparative in its goals and nature: therefore, it is invalidated only if conditions differ between the treatments being compared. That was not the case of soil moisture content, given that soil type was the same and that soil and weather conditions remained the same all along the duration of the study, so that it was very unlikely that soil got wetter or dryer in the time elapsed between the application of one treatment and that of the other one.
COMMENT 15: L178 – manuscript title implies skidder only, but now it appears that the soil component is across the entire harvest area – this is confusing
RESPONSE 15: We have changed the title, so that its new formulation includes the whole skidding operation, not the skidder only.
COMMENT 16: 185 – soil survey classifications in table 1 do not address soil compaction;
RESPONSE 16: True. But we actually never stated we would attempt an assessment of soil compaction. The soil disturbance assessment method we have used in this study is properly referenced and has been used in many studies for the same purpose – assessing soil disturbance, not soil compaction. Assessing soil compaction was not our intention, nor we ever stated such intention.
COMMENT 17: not clear how depth of rutting was measured; the degree of rutting is influenced by soil moisture, but soil moisture was not measured.
RESPONSE 17: Rutting depth was measured simply with a stick and a ruler (the stick placed across the rut at ground surface level, and the ruler to take the perpendicular distance between the stick and the bottom of the rut). Concerning soil moisture content, please see RESPONSE 14.
COMMENT 18: Why would you expect soil disturbance when there is logging slash?
RESPONSE 18: I believe we may have a different interpretation of the term “soil disturbance”. From the statement above, I assume the Reviewer uses the term “soil disturbance” as indicating soil scalping, mixing and rutting (and possibly compaction, too). In contrast, we used that term as described in the studies we have quoted, and in the instructions attached to the survey protocols we used: there, the terms includes all forms of alteration of the soil surface, including covering with slash. In fact, we clearly stated in our manuscript: “Visual classes were used to simplify and standardize the assessment of soil disturbance, defined as the degree of change from natural conditions [32, 33].” At any rate, we have changed the table caption so that it now refers to a generic “soil survey”, which is a more general and less debatable description.
COMMENT 19: Was slash distributed over skid trails as a BMP?
RESPONSE 19: Not at the time when we conducted our soil survey. That was likely done after the operation was concluded, but we were not there to check that.
COMMENT 20: Table 7 is confusing. It provides percentages for before and after skidding, yet the measurements were not limited to skid trails, but rather the entire harvest area.
RESPONSE 20: We have revised the table caption to avoid any such confusion.
COMMENT 21: Generally, the soil component of this paper is confusing and does not fit well. It should be another paper.
RESPONSE 21: We respectfully disagree: We explicitly stated that “The goal of this study is to contribute to our knowledge of winch-assist skidding, as used in a typical plantation forestry site with moderate to steep terrain. In particular, the study aimed at determining the impact of winch-assistance on 1) productivity and 2) soil disturbance”. Therefore, soil disturbance is indeed a component of the study, and in the Introduction section we have explained why it should be included in any assessment of winch assist technology. For that reason, we believe that its inclusion in the study is fully legitimate.
COMMENT 22: When reporting the results of the GLM model, please add coefficient estimates (with the positive/negative sign) and standard errors for each variable in Tables 4 and 6. In addition, the Error DF and the SS need to be explained.
RESPONSE 22: Unfortunately, the Minitab output tables for the GLM analysis do not show those coefficients, but just the indicators we reported in Tables 4 and 6. I believe there must be a way to actually get the software to show them but learning how to do that would take more time than it is allowed by the deadline for this revision. Furthermore, what is essential to the analysis is actually the F and P values, which tell us whether the differences between the means shown in the other tables are statistically significant or not. For those reason, we ask the Reviewer to be patient and accept our apologies for not (having the time of) doing what he/she asks. While the additional information he/she asks for would be useful, it is not essential to the stated goals of this study. On the other hand, we have explained the meaning of the abbreviations DF and SS, as requested.
COMMENT 23: L219 – how was load size monitored? Did the skidder operator have discretion to increase load size with winch-assist versus without? Or was load size pre-determined by the shovel operator setting up bunches?
RESPONSE 23: In fact, loads were formed by the loader operator at the trail side, but load size was agreed between him and the skidder operator, based on perceived skidder capacity. We have introduced a hopefully better description of how loads were formed in the revised manuscript version.
COMMENT 24: L245 – using winch always resulted in larger load size; again, was this a judgement call on the part of skidder operator?
RESPONSE 24: Please see the response above.
COMMENT 25: L261 – the fine-tuning of load size needs more explanation
RESPONSE 25: Sure. We have rephrased our sentence and we hope the new version is clearer than the old one.
COMMENT 26: L267 – Figure 2 – counter-intuitive that “steep wa” would have the lowest productivity; the higher payloads should compensate for longer skid times
RESPONSE 26: It is counter-intuitive, or at least against our expectations. We have tried to produce a plausible explanation in the Discussion section. All things considered, I believe that this counter-intuitive finding makes the paper more interesting, and forces us to stretch our intellects to find an explanation. Probably, the paper would have been less interesting and the discussion less engaging, if the results would have just confirmed expectations…
COMMENT 27: L295 – I could not find figure 3. Figure 4 is not referenced in the text. The figure 4 caption needs to be more descriptive. Make it clear that the x-axis represents one hour.
RESPONSE 27: Apologies. We made an absolute mess of figure numbering…The fact is that the original version contained way too many figures, so we reduced that number. However, that created some confusion with the referencing. We have thoroughly checked the sequential numbering and restored consistency, as suggested.
COMMENT 28: L372 – this study does not assess cost-effectiveness
RESPONSE 28: Correct. The actual meaning we wanted to convey in that sentence was that by using our productivity increment figures, prospective users can balance the pros and cons of introducing winch assist technology to their operations. We acknowledge that our phrasing was ambiguous, and we have rephrased our sentence accordingly.
COMMENT 29: L388 – the role of the skidder operator is critical to results; setting tension is one variable, but also need to discuss load size;
RESPONSE 29: I think we just did when we stated ““A second explanation is a deliberate action of the driver, who after experiencing machinery problems may have held back on loading for fear of exceeding machine capacity, while he should have formed larger loads than he did, once under the winch assist treatment”. In our understanding, this sentence states that the driver had a crucial role in deciding load size and that he may have underestimated the capacity of his machine when tethered. If the Reviewer thinks this sentence is inadequate to convey the intended meaning, then I would kindly ask him/her to suggest an alternative, because I cannot come with a better version myself (but that may be a classic example of “writer’s rut”, when the writer gets stuck with that one sentence that makes the best sense to him, while being incomprehensible to others!).
COMMENT 30: L395 – perhaps the skidder operator was too conservative with load size decision with winch assist
RESPONSE 30: Yes, we agree. The Reviewer is certainly right. In fact, just few lines above we stated “A second explanation is a deliberate action of the driver, who after experiencing machinery problems may have held back on loading for fear of exceeding machine capacity, while he should have formed larger loads than he did, once under the winch assist treatment”.
Round 2
Reviewer 2 Report
The authors have done an adequate job of addressing my minor concerns throughout the paper; however, they chose to keep the soil disturbance component.
I maintain that this component does not fit well with the winch-assist technology component for skidders. The productivity of winch-assist for skidders is the primary purpose of this study and should be the focus of the paper. The soil disturbance data goes beyond the skidder, and includes other harvesting machinery. The methods for soil disturbance are not rigorous and the results do not make a significant contribution to the literature.
I accept the paper with winch-assist only.
I do not accept the paper if the soil component remains.
Author Response
COMMENT 1: The authors have done an adequate job of addressing my minor concerns throughout the paper; however, they chose to keep the soil disturbance component.
I maintain that this component does not fit well with the winch-assist technology component for skidders. The productivity of winch-assist for skidders is the primary purpose of this study and should be the focus of the paper. The soil disturbance data goes beyond the skidder, and includes other harvesting machinery. The methods for soil disturbance are not rigorous and the results do not make a significant contribution to the literature.
I accept the paper with winch-assist only.
I do not accept the paper if the soil component remains
RESPONSE 1: We are sorry that the distinguished Reviewer has such a poor opinion of our work with the soil survey. We acknowledge the fact that soil disturbance was not the primary goal of the study and that the method we adopted for gauging soil disturbance only offers a partial picture. We never intended to perform a dedicated soil disturbance study. However, given the many other studies stressing the effect of winch-assistance on soil disturbance, we wanted to offer some preliminary information on that, too. We spent time and effort on our soil survey, which we still feel was adequate to the limited goals it was meant to achieve. It would be sad to throw it all away. In our further revision, we have introduced a caveat that stresses the limits of our soil survey, so that readers can interpret its results correctly and are warned against extrapolating them beyond their limited scope. I hope this compromise solution is acceptable to the Reviewer, so that we can meet halfway.
