the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Allometric equations and wood density parameters for estimating aboveground and woody debris biomass in Cajander larch (Larix cajanderi) forests of Northeast Siberia
- Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
- Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
Abstract. Boreal forests are particularly vulnerable to climate warming which increases the occurrence of natural disturbances, such as fires and insect outbreaks. It is therefore essential to better understand climate-induced changes in boreal vegetation dynamics. This requires accurate estimates of variations in biomass across regions and time. This remains challenging in the extensive larch forests of Northeast Siberia because of the paucity of allometric equations and physical properties of woody debris needed for quantifying aboveground biomass pools from field surveys. Our study is the first to present values of mean squared diameter (MSD) and specific gravity that can be used to calculate fine dead and downed woody fuel loads in Cajander larch (Larix cajanderi) forests using the line-intersect sampling approach. These values were derived from field measurements collected in 25 sites in the Republic of Sakha, Russia, and compared with values reported for other prevalent boreal tree species. We developed allometric equations relating diameter at breast height (DBH) to stem wood, stem bark, branches, foliage, and aboveground biomass based on measurements of 63 trees retrieved from previous studies. Differences between our allometric models and existing equations were assessed in predicting larch aboveground biomass in 53 sites sampled in the Republic of Sakha. We found that using fine woody debris (FWD) parameters from other boreal tree species and allometric equations developed in other regions may result in significant underestimates of fuel biomass in larch-dominated forests of Northeast Siberia. The FWD parameters and allometric equations presented in our paper can be used to refine estimates of aboveground biomass in Cajander larch forests in Northeast Siberia.
Clement Jean Frédéric Delcourt and Sander Veraverbeke
Status: final response (author comments only)
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RC1: 'Comment on bg-2022-80', Anonymous Referee #1, 12 Apr 2022
Dear. Editor
The current paper aims to parameterize i) allometric questions for aboveground biomass using an existing database and ii) an equation to estimate woody debris on the forest floor using data based on field survey, for Siberian Larix cajanderi.
Authors demonstrate significant spatial variations of biomass of standing trees and woody debris estimates on the forest floor, depending on equations and parameters, comparing their estimated parameters with published ones. They come to the conclusion that the developed functions can be applicable to the species in Siberian forests.
I consider that the paper would fail to fit within the journal’s scope as well as may fail to attract a broad readership, because i) the study develops a tool, with no application of the tool, thus to fail to draw geo- or biological conclusion, ii) even the developed tools are only appliable at a relatively small scale, as no testing for the feasibility of a large scale application was made, while such tools for a large scale application already exist from national to continental scales, and iii) the estimated parameters were unjustly compared with published parameters, as to overfitting and comparing between different population distributions; for example, published equations were based on smaller and older trees, compared to the data set, based on which allometric questions were developed.
Here come specific comments.
L 15. “… at breast height (DBH)”
Depending on regions, the breast height differs. Specify the height (m).
L51. “The line-intersect…”
Authors may begin a new paragraph before “The line- …”
2.1 Fine woody debris sampling
This section may be expanded and articulated. For example, papers that have been cited here (Sackett 1980; Van Wagner 1982; Nadel et al. 1997; 1999) articulate the formulation. Because the formulation is of great importance in the paper, it has to be well explained, and readers would not want to check back those papers to understand the formulation and meanings of parameters.
L130. Volume of a sample was first dried and then estimated. Would it underestimate volume of the sample due to shrinkage during drying?
L 305. Figure 3.
I would recommend to add data points in the figures. Ranges of the independent variable (DBH) differ significantly between functions. For example, DBH in Yakutia ranges 1.9 – 18.9 cm, while DBH in Magadan ranges 3.9 – 52.8 cm. Comparing and merging two populations, each of which has a different DBH distribution, may result in a bias outcome. Moreover, it is invalid to compare it with other published studies, where the populations of size and age of sample trees were out of the current study samples’ distribution.
L325. Figure 4.
The meaning of error bars needs to be explained. And how can the estimates of aboveground biomass be 0 (lower ending of the estimates are all 0)?
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AC1: 'Reply on RC1', Clement Delcourt, 02 Jun 2022
Dear reviewers and editor,
Thank you for considering our manuscript for publication in Biogeosciences. We appreciate your valuable comments.
First, we explain which major changes we plan in the revision and respond to some of criticisms of reviewer 1. Second, we highlight the major contributions of our paper. Third, we respond point-by-point to the reviewers’ comments.
Reviewer 1 and 2 both commented that it may not be feasible to pool the data from the two different sites given the differences in stand age and structure between the sites. After considering this comment, we agree with the reviewers. We will therefore remove the site-common allometry in the revision.
Reviewer 1 asserts that our paper may not fall within the scope of Biogeosciences. We respectfully disagree with this assessment. On the webpage of Biogeosciences, the aims and scope of the journal states an interest in work on 'all aspects of the interactions between the biological, chemical, and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere, and atmosphere' (https://www.biogeosciences.net/about/aims_and_scope.html). Aboveground forest biomass and carbon storage are critical components at the interface of the biosphere and atmosphere, and further influence processes in the hydrosphere (e.g., through plant-water interactions), pedosphere (e.g., through nutrient cycling) and cryosphere (e.g., through influences on snow cover) among others.
The major contributions of our paper are (including the planned revisions):
- The first ever published wood density measurements that allow to calculate fine woody debris biomass in Cajander larch forests of Northeastern Siberia.
- A significant increase (from 3 to 5) in the number of available allometric equations to calculate tree biomass in Cajander larch forests of Northeastern Siberia. The previously published equations (Kajimoto et al., 2006; Alexander et al., 2012) do not include bark as a biomass pool. This is another important addition of our work, as quantifying bark biomass is important (e.g., bark and wood have different combustion processes; Lestander et al., 2012).
We want to stress that our contributions are focused on an extremely data-poor region, Northeastern Siberia larch forests, which encompass about 20 % of the boreal forest and are of global importance. Unfortunately, with the current political situation, it may not be easy for scientists to make measurements in Russia or exchange data with scientists from Russian institutes in the near future. Our paper provides a number of equations and parameters, in easily accessible manner, that will be of interest to anyone studying biomass and carbon stocks of Cajander larch forests in Siberia, and more broadly the boreal forest. We sincerely hope that more data on Cajander larch forests will become available in the future, so that this work can further be advanced. We have nuanced our statements with regards to the use of the data and equations in our paper and included this future perspective.
The point-by-point responses are given in the attached pdf.
Sincerely,
Clement Delcourt & Dr. Sander Veraverbeke
Lestander, T. A., Lundström, A., and Finell, M.: Assessment of biomass functions for calculating bark proportions and ash contents of refined biomass fuels derived from major boreal tree species, Can. J. Forest Res., 42, 59–66, doi:10.1139/x11-144, 2012.
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AC1: 'Reply on RC1', Clement Delcourt, 02 Jun 2022
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RC2: 'Comment on bg-2022-80', Anonymous Referee #2, 15 Apr 2022
The authors of Allometric equations and wood density parameters for estimating aboveground and woody debris biomass in Cajander larch (Larix cajanderi) forests of Northeast Siberia observed mean squared diameter and specific gravity. They developed allometric equations at 25 sites in the Republic of Sakha in Russia. They then make comparisons to allometric equations developed in other studies. Overall the methods appear rigorous. This study provides valuable information from an important yet remote region of the world from which little in-situ data is available and makes the case that further data collection efforts are needed. My major concern is that the claim that the allometric equations presented in the text are more generally applicable needs to be better supported or more nuanced. The equations and the comparison of them to other previously developed equations are not validated against in situ data or across a larger region of space. It seems that the equations from earlier work would be more applicable than those developed by the authors in some more northeastern regions or specific stand types, especially near where they were developed. This is very problematic given the manuscripts focus on providing generalized equations to improve our ability to estimate above-ground biomass in this region.
L95 introduction: I suggest highlighting some of the other roles that this data could play (previously mentioned around L35) to strengthen the introduction.
L140: Is there a citation for the two equations above. Also, some brief explanation of why the samples were dipped in paraffin could be useful.
L205-210: I suggest including a bit more information about this fitting method and selecting the exponent c, including references to other work that uses this method. It could also be useful to include these residual plots in the appendix.
Figure 3: It would be good to include the data points on this plot where possible and the standard error envelopes for the fits. These lines are also somewhat difficult to distinguish when printed in black and white.
L206: I think table A1 is important and merits inclusion in the text. It could be interesting to see this comparison done differently. For example, calculating fuel loads at one of the study sites using these different parameters and then plotting the values could better illustrate their importance in percentage terms.
L310: The Magadan site has many more samples than the Yakutian site, although the size range of the available samples varies. Given the conclusion that allometry is somewhat region-specific, it could be interesting to see the result of a fit where this imbalance of samples is corrected using weighting.
Figure 4: For this box plot of the site observations, it would be good to explain the quantiles, etc. shown in the figure caption
L315: Some additional summary information for these 53 sites could be useful (i.e., the mean, sd, and range of dbh)
L315-320, 350-365: I suggest heavily revising these sections of the paper. The claim that the other allometric equations underestimate aboveground biomass or are more generally applicable seems too strong. The actual aboveground biomass of the 53 comparison sites is not truly known. From the text or maps, it's unclear where exactly these test sites are located and how close they are to the sites from Siewert 2015. The comparison to Siewet 2015 is not emphasized in the text. This point would be much stronger if some additional non-allometry-derived data sources, more information from the literature, etc., were included as validation. It could also be interesting to see this comparison done across multiple sites. I imagine these other two equations will perform better in certain areas or stand types. Such a comparison would add more depth to the point about how generalizable each set of equations is.
L330-340: Interpreting the fitted allometric parameters (i.e., as in Niklas 1994) here and further discussing the differences in climate and other properties between the sites could strengthen the conclusions in this section.
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AC2: 'Reply on RC2', Clement Delcourt, 02 Jun 2022
Dear reviewers and editor,
Thank you for considering our manuscript for publication in Biogeosciences. We appreciate your valuable comments.
First, we explain which major changes we plan in the revision and respond to some of criticisms of reviewer 1. Second, we highlight the major contributions of our paper. Third, we respond point-by-point to the reviewers’ comments.
Reviewer 1 and 2 both commented that it may not be feasible to pool the data from the two different sites given the differences in stand age and structure between the sites. After considering this comment, we agree with the reviewers. We will therefore remove the site-common allometry in the revision.
Reviewer 1 asserts that our paper may not fall within the scope of Biogeosciences. We respectfully disagree with this assessment. On the webpage of Biogeosciences, the aims and scope of the journal states an interest in work on 'all aspects of the interactions between the biological, chemical, and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere, and atmosphere' (https://www.biogeosciences.net/about/aims_and_scope.html). Aboveground forest biomass and carbon storage are critical components at the interface of the biosphere and atmosphere, and further influence processes in the hydrosphere (e.g., through plant-water interactions), pedosphere (e.g., through nutrient cycling) and cryosphere (e.g., through influences on snow cover) among others.
The major contributions of our paper are (including the planned revisions):
- The first ever published wood density measurements that allow to calculate fine woody debris biomass in Cajander larch forests of Northeastern Siberia.
- A significant increase (from 3 to 5) in the number of available allometric equations to calculate tree biomass in Cajander larch forests of Northeastern Siberia. The previously published equations (Kajimoto et al., 2006; Alexander et al., 2012) do not include bark as a biomass pool. This is another important addition of our work, as quantifying bark biomass is important (e.g., bark and wood have different combustion processes; Lestander et al., 2012).
We want to stress that our contributions are focused on an extremely data-poor region, Northeastern Siberia larch forests, which encompass about 20 % of the boreal forest and are of global importance. Unfortunately, with the current political situation, it may not be easy for scientists to make measurements in Russia or exchange data with scientists from Russian institutes in the near future. Our paper provides a number of equations and parameters, in easily accessible manner, that will be of interest to anyone studying biomass and carbon stocks of Cajander larch forests in Siberia, and more broadly the boreal forest. We sincerely hope that more data on Cajander larch forests will become available in the future, so that this work can further be advanced. We have nuanced our statements with regards to the use of the data and equations in our paper and included this future perspective.
The point-by-point responses are given in the attached pdf.
Sincerely,
Clement Delcourt & Dr. Sander Veraverbeke
Lestander, T. A., Lundström, A., and Finell, M.: Assessment of biomass functions for calculating bark proportions and ash contents of refined biomass fuels derived from major boreal tree species, Can. J. Forest Res., 42, 59–66, doi:10.1139/x11-144, 2012.
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AC2: 'Reply on RC2', Clement Delcourt, 02 Jun 2022
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RC3: 'Comment on bg-2022-80', Anonymous Referee #3, 03 Jun 2022
This manuscript describes the size-class-dependent characteristics of fine woody debris according to their detailed field experiment, and the new allometric relationship by using literature data, for the Cajander larch forest in Northeast Siberia. Since such data in this region (central Yakutia) is limited, this manuscript will contribute a lot to future modeling and remote sensing studies in this region. I've already seen the comments from the two reviewers and the author's replies, so I'd like to add some minor comments about what I'm still unsure about.
About fine woody debris:
The authors show the MSD and specific gravity of Cajander larch for each diameter size class.
On the other hand, they compared their single factor M with other species in different regions in Table A1, but it is shown in the percentage difference by size class, not the actual values of M. I think the single factor M and the fuel load W can be the important outcomes of this study, so I suggest the authors show these results.Equation (1):
- Even though the final answer is correct, I strongly suggest you adopt the consistent units in the equation. Specifically, the unit of QMD should be [m], not [cm], and the equation should be multiplied by 104 to convert the unit from [Mg m-2] to [Mg ha-1]. This will avoid confusion by the readers and avoid careless mistakes in calculation.
- Secant (sec) should be in non-italic.
- Is Gi the arithmetic mean of G (specific gravity) within the diameter size class i?
- Is hi the arithmetic mean of h (piece tilt angle) within the diameter size class i? If yes, is it mathematically correct to calculate the secant using the arithmetic mean value of h for obtaining the fuel load?
- For example, If h takes 0 degrees and 180 degrees, the arithmetic mean of them can be 90 degrees.
- Besides, according to Fig. 2, h is always related to the diameter of each sampled piece, so I think the product of the diameter and sec h should be used for the statistical calculation.
- If N represents the (total) number of intercepts over the length of the transect line, what does Ni mean?
Equation (2):
- I suggest using a single character (e.g., α) instead of "slope" to represent the ground slope.
- (tan α)2 is generally written as tan2α.
Equation (3) and L140:
- The authors use two characters to represent the specific gravity. One is G in equation (1) and L104 (kg m-3), and another is S here (g cm-3).
L158-159, equation (5):
- Does a single factor M represent the fuel loads per intercept (sample) on the transect line? Please explain this concept concisely since the reference (Nalder et al., 1999) was not accessible from my environment.
- If you share the same units with equation (1), Gi has the unit of [Mg m-3], and MSDi might have the unit of [cm2]. However, the author specified that M has the unit of [g cm-1]. In this case, the units of the left and right sides of equation (5) are inconsistent. I suppose the unit of Gi in equation (5) would be [g cm-3], or it should be Si according to equation (3).
- As pointed out in equation (1), I still wonder whether the use of “sec hi” is mathematically correct if hi represents the arithmetic mean of h in class i.
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AC3: 'Reply on RC3', Clement Delcourt, 23 Jun 2022
Dear reviewers and editor,
Thank you for considering our manuscript for publication in Biogeosciences. We appreciate your valuable comments.
The point-by-point responses to reviewer 3 ‘s comments are given in the attached pdf.
Sincerely,
Clement Delcourt & Dr. Sander Veraverbeke
Clement Jean Frédéric Delcourt and Sander Veraverbeke
Clement Jean Frédéric Delcourt and Sander Veraverbeke
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