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: open (until 28 May 2022)
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RC1: 'Comment on bg-2022-80', Anonymous Referee #1, 12 Apr 2022
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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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RC2: 'Comment on bg-2022-80', Anonymous Referee #2, 15 Apr 2022
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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.
Clement Jean Frédéric Delcourt and Sander Veraverbeke
Clement Jean Frédéric Delcourt and Sander Veraverbeke
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