Carbon Pools in a 77 Year-Old Oak Forest under Conversion from Coppice to High Forest

Round 1

Reviewer 1 Report

The paper entitled as “Carbon pools in a 77 years-old oak forest under conversion 2 from coppice to high forest” estimate forest carbon and its meanings of CO2 sequestration and its trade-off between carbon stock and energy use of woods. Firstly, the contents of this study is typical and do not have new scientific view or outcomes. But, this study will fill the gap of old secondary forest’s carbon data. Considering journal’s objectives, I would give above basic comments and details comments as follows and suggest major revision before accepting.

1. Additional literatures should be reviewed and added. Following paper analyze trade-off of secondary forest management and analyze soil carbon in detail.

Hiratsuka, M., Hatakeyama, K., Ohkubo, T., & Takeuchi, D. (2020). Dynamics of secondary forest and its perspective under the Satoyama system in Saitama prefecture, Japan. Journal of Forest Research, 25(1), 51-57.

2. Equation in this paper should be revised according to specific equation tool.

3. Some parts of CO2 in this paper should be revised into CO₂. Also, other units (e.g. m2) should be revised to m².

4. According to IPCC Guidelines, the Authors should refer carbon pool of harvest wood products (HWP). If target secondary forest is under silvicultural aspect, HWP is very important.

5. Again, parts of Introduction and Discussion, I would request some kind of additional scientific view. Because this study is very typical and it is hard to have additional knowledge. In my view, it will be better to discuss according to EU forestry policy regarding the relationship between silviculture or energy demand and how to manage old secondary forest more deeply. It means to add more political aspects. 

Author Response

REVIEWER  1

Comments and Suggestions for Authors

The paper entitled as “Carbon pools in a 77 years-old oak forest under conversion from coppice to high forest” estimate forest carbon and its meanings of CO2 sequestration and its trade-off between carbon stock and energy use of woods. Firstly, the contents of this study is typical and do not have new scientific view or outcomes. But, this study will fill the gap of old secondary forest’s carbon data. Considering journal’s objectives, I would give above basic comments and details comments as follows and suggest major revision before accepting.

Authors’ responses

Authors would like to express their thanks to the Reviewer for their time spent reviewing this manuscript and for the valuable comments that greatly improved the quality of the ms. All the comments were considered in the revision of the manuscript.

As concern as the value of the scientific outcomes presented in the current study, authors would like to point out that these clearly indicate an annual C gain from the conversion of coppice forest to high forest through the long-term systematic forest management and with the application of specific silvicultural treatments (selective fellings). These outcomes are very scarce worldwide, especially for temperate deciduous oak forests, and thus they can be considered very valuable, since they show a reliable way for specific long-term forest management that is highly effective in increasing forest carbon sequestration rates.

 

Analytical authors’ responses to the Reviewer comments.

Reviewer comment

1. Additional literatures should be reviewed and added. Following paper analyze trade-off of secondary forest management and analyze soil carbon in detail.

Hiratsuka, M., Hatakeyama, K., Ohkubo, T., & Takeuchi, D. (2020). Dynamics of secondary forest and its perspective under the Satoyama system in Saitama prefecture, Japan. Journal of Forest Research, 25(1), 51-57.

Authors’ responses

Thank you for the valuable comment. Both introduction and discussion were extensively revised according to your suggestion.

 

Reviewer comment

2. Equation in this paper should be revised according to specific equation tool.

Authors’ responses

Thank you for your comment. We made the improvement in the revised text.

 

Reviewer comment

3. Some parts of CO2 in this paper should be revised into CO2. Also, other units (e.g. m2) should be revised to m2.

Authors’ responses

Thank you for your comment. We made all the corrections along the revised text.

 

Reviewer comment

4. According to IPCC Guidelines, the Authors should refer carbon pool of harvest wood products (HWP). If target secondary forest is under silvicultural aspect, HWP is very important.

Authors’ responses

Thank you for your valuable comment. We added the requested data. Please see lines 473-477 in the revised text.

 

Reviewer comment

5. Again, parts of Introduction and Discussion, I would request some kind of additional scientific view. Because this study is very typical and it is hard to have additional knowledge. In my view, it will be better to discuss according to EU forestry policy regarding the relationship between silviculture or energy demand and how to manage old secondary forest more deeply. It means to add more political aspects.

Authors’ responses

Thank you for the valuable comment. Both introduction and discussion were extensively revised in the revised manuscript, according to the suggestions of both Reviewers. Also, please see our responses to your general comment.

Reviewer 2 Report

I have read the article and recognized that it has useful for forest management and climate change mitigation contributions. However, the authors need to respond and incorporate the reviewer's comments carefully for further process of the article.

1.      The coppice conversion results in a large accumulation of carbon in all ecosystem pools. Why?

2.      The allometric equation that the author developed is only using the DBH parameter where is the Height and wood density?

3.      Did the authors use the allometric equations for estimation of the allometric equations or use the standard formula developed by Chave et al., 2014 and brown 1997?

4.      Authors need to show the use of estimating carbon pool associated with carbon trading, CDM and REDD+

5.      The destructive method is not recommended for the development of an allometric equation; it is better to use the semi-destructive method but researchers used the destructive which is opposed to the environmental principles.

6.      Figure 1 needs to modify and provide a clear location of the study area what is the need for figure 2 in this place?

7.      The authors need to clarify the sampling techniques. How sampling was taken for field measurement and how many sample plots were taken?

8.      For measurement of dead wood, four plots were established, is it real? Is it representative of the area? For all pools, the sample determination method is required!

9.      The soil sampling method must be a standard and scientific way of carbon analysis. I have questions about the sampling size of soil sampling and also the composite method required to be standard carbon analysis. The volume, bulk density and laboratory procedure of soil carbon analysis must be stated

10.  Independent variables tested were: tree diameter at breast height (DBH),  total height (H), crown base height (CBH), and crown length (CL) but the authors tested only DBH and we did not see the height and CBH including CL.

11.  How many trees were sampled? Are they representatives? Recognized latter!

12.  Lone 303-304 “According to the measurements of 1692 trees found in the four sampled plots, as well  as the analysis of the tree annual rings of 12 sampled trees, the studied forest is even-aged,  77 years old, and probably coming from the resprouting of the previous mature trees.” It seems method

13.  In table 1 the sand volume of a tree is 270.93 m³. This is out of reality. A tree having a DBH of 15.49  cm and a height of 12.97 m can not be a volume of 270.93 m³. Do the data need to see analysed again, please?

14.  The biomass prediction or allometric  equation must have come first in the result part and then followed the carbon estimation

15.  Did you compare the allometric equation you developed with the standard Internation allometric equation such as Chave, brown or any local allometric equation? If the biomass estimated using your developed allometric equation is showing a significant difference then your equation validity becomes low.  

Author Response

REVIEWER  2

Comments and Suggestions for Authors

I have read the article and recognized that it has useful for forest management and climate change mitigation contributions. However, the authors need to respond and incorporate the reviewer's comments carefully for further process of the article.

Authors’ responses

Authors would like to express their thanks to the Reviewer for their time spent reviewing this manuscript and for the valuable comments that greatly improved the quality of the ms. All the comments were considered in the revision of the manuscript.

 

Analytical authors’ responses to the Reviewer comments

Reviewer comment

1. The coppice conversion results in a large accumulation of carbon in all ecosystem pools. Why?

Authors’ responses

Indeed, the results of the study prove that. The theoretical explanation is given in the text (please, see the lines 68-81 in the revised ms).

 

Reviewer comment

2. The allometric equation that the author developed is only using the DBH parameter where is the Height and wood density?

Authors’ responses

Thank you for this reasonable question. In fact, we tested a lot of linear and non-linear equations for biomass estimation, as well as the commonly used independent variables (please, see the relevant subsection “2.4 Statistical analysis of the Method section).  After the statistical testing we selected the most scientifically correct equation and the most appropriate independent variables entered in the model equations, based on the commonly used statistical criteria.

 

Reviewer comment

3. Did the authors use the allometric equations for estimation of the allometric equations or use the standard formula developed by Chave et al., 2014 and brown 1997?

Authors’ responses

We tested a lot of linear and non-linear equations for biomass estimation (please, see the relevant subsection “2.4 Statistical analysis of the Method section) considering the existed worldwide literature. The suggested standard formula developed by Chave et al., (2014) was considered, but we did not mention it because it concerns tropical forests, while our study deals with temperate forest. However, in the Method section we cite more than 10 works presenting allometric equations for estimation of forest biomass of temperate ecosystems.  After statistical testing we selected the most scientifically correct equation and the most appropriate independent variables, based on the commonly used statistical criteria.

 

Reviewer comment

4. Authors need to show the use of estimating carbon pool associated with carbon trading, CDM and REDD+

Authors’ responses

We added some relevant text in order to connect the findings of our study to  REDD+ forum (please, see the lines 43-46, and 479-787 in the revised ms).  However, we have to note that Greece is not a member of this forum.

 

Reviewer comment

5. The destructive method is not recommended for the development of an allometric equation; it is better to use the semi-destructive method but researchers used the destructive which is opposed to the environmental principles.

Authors’ responses

Τhe authors agree with the reviewer's point of view, however, the destructive sampling is a basic necessary tool for the development of reliable scientific approaches for biomass estimation, and it should be used when it is absolutely necessary.

 

Reviewer comment

6. Figure 1 needs to modify and provide a clear location of the study area what is the need for figure 2 in this place?

Authors’ responses

Ok, the Figure 1 was modified and now provide a clear location of the study area.

Also, (the previous) Figure 2 was removed.

 

Reviewer comment

7. The authors need to clarify the sampling techniques. How sampling was taken for field measurement and how many sample plots were taken?

Authors’ responses

We added the necessary information in the analytical description of the sampling technique given in the Method section. Please, see the lines 228, 259-260,  267-268, and 293-296, in the revised text.

 

Reviewer comment

8. For measurement of dead wood, four plots were established, is it real? Is it representative of the area? For all pools, the sample determination method is required!

Authors’ responses

The dead wood was measured throughout the plot area in the same four plots established for aboveground living biomass (AGB) biomass. Litter and soil measurements were carried out according to relevant literature. However, more details were added in order to give a more analytical method’s description (please, see the lines 228, 259-260,  267-268, and 293-296, in the revised text).

 

Reviewer comment

9. The soil sampling method must be a standard and scientific way of carbon analysis. I have questions about the sampling size of soil sampling and also the composite method required to be standard carbon analysis. The volume, bulk density and laboratory procedure of soil carbon analysis must be stated.

Authors’ responses

We improved the description of soil sampling (please see the lines 259-260,  267-268, and 293-296 of the revised text), according to the suggestions.

 

Reviewer comment

10. Independent variables tested were: tree diameter at breast height (DBH),  total height (H), crown base height (CBH), and crown length (CL) but the authors tested only DBH and we did not see the height and CBH including CL.

Authors’ responses

In the Method section, and more specifically in the subsection “2.4 Statistical analysis”, we describe analytically the independent variables we used in the performed statistical analysis and the whole process for the selection of the model equation. In fact, we used all the mentioned variables, but finally the most important independent variable was DBH, which was finally entered in the model equation. The criteria used for the final model selection was the (corrected) coefficient of determination (r²), the significance value of F test and the significance level of each coefficient (p-value). Additionally, the average relative error (%) of the predicted values was estimated.

 

Reviewer comment

11. How many trees were sampled? Are they representatives? Recognized latter!

Authors’ responses

Τhank you for the comment; however, the number of the sampled trees and the whole field sampling method are clearly described in the Method section (please, see the lines 186-196 of the revised text).

 

Reviewer comment

12. Line 303-304 “According to the measurements of 1692 trees found in the four sampled plots, as well  as the analysis of the tree annual rings of 12 sampled trees, the studied forest is even-aged,  77 years old, and probably coming from the resprouting of the previous mature trees.” It seems method

Authors’ responses

Τhank you for the comment. We appropriately modified the text (lines 332-333 in the revised text).

 

Reviewer comment

13. In table 1 the sand volume of a tree is 270.93 m³. This is out of reality. A tree having a DBH of 15.49  cm and a height of 12.97 m can not be a volume of 270.93 m³. Do the data need to see analyzed again, please?

Authors’ responses

The value of 270.93 m³ concerns the stand volume per hectare and it does not concern a tree volume. We slightly modified the form of the Table 1, in order to clarify the confusion.

 

Reviewer comment

14. The biomass prediction or allometric equation must have come first in the result part and then followed the carbon estimation

Authors’ responses

Thank you for the comment. In fact, this is already done; the subsection of the Results “3.2.1. Biomass prediction allometric equations” concerns the allometric equation while the next subsection  “3.2.2. Estimation of aboveground living biomass at stand level” concerns the carbon estimation per hectare (at forest stand level).

A modification was made in the title of the subsection in order to clarify it.

 

Reviewer comment

15. Did you compare the allometric equation you developed with the standard Internation allometric equation such as Chave, brown or any local allometric equation? If the biomass estimated using your developed allometric equation is showing a significant difference then your equation validity becomes low.  

Authors’ responses

The subsection “2.4 Statistical analysis” of the Method section describes the process we followed, while the relevant theoretical background is set in the introduction (please, see the lines 109-123 of the revised text).

Round 2

Reviewer 1 Report

the current manuscripot had been improved.

Reviewer 2 Report

Accepted!