the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Aug 2026
Effect of initial pools on carbon balance calculations – a case of larch plantations in northeastern China
Abstract. Carbon dioxide (CO2) released during the decomposition of harvest residues reduces the net carbon sequestration of stands planted on clear-felled sites. All other dead organic materials (DOM) present in the stand, such as litter and dead trees, also decompose and release CO2 into the atmosphere. Carbon is also released when discarded wood products made from previously harvested wood decay. Carbon sequestration is overestimated, especially in young stands, if the CO2 released from DOM and discarded wood products is ignored in calculations. This study developed models to predict the biomass of DOM pools in the stand and the remaining biomass of products made from previously harvested wood. Initializing these biomass pools with the models and simulating DOM decomposition and product disposal helps eliminate overestimates in the carbon sink calculations for young plantations. When these models were integrated into simulation software, it showed that a young larch stand planted on a clear-felled site acts as a carbon source for about 10 years. Thinning treatments convert the stand into a carbon source for 3–7 years. Optimization with carbon subsidies and taxes indicated that higher CO2 prices extend the optimal rotation length and increase the average carbon stock of the rotation. However, carbon pricing never turned the stand into a permanent carbon sink. Carbon sequestration in Chinese plantation forests can be improved by reducing thinning and increasing rotation lengths. The positive effects last as long as it takes to adopt the revised management practices across all forests.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2026-4236', Anonymous Referee #1, 24 Sep 2026
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AC1: 'Reply on RC1', Xingji Jin, 08 Oct 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4236/egusphere-2026-4236-AC1-supplement.pdf
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AC1: 'Reply on RC1', Xingji Jin, 08 Oct 2026
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RC2: 'Comment on egusphere-2026-4236', Anonymous Referee #2, 28 Sep 2026
General comments
The paper by Jiang et al. exposes the results of a new model aiming at better taking into account the decomposition of harvest residues when calculating CO2 sequestration after planting new larch trees in clear-felled sites. It highlights that the CO2 sequestration is often overestimated, as the decomposition of the residues can generate a lot of carbon dioxide which is usually unaccounted for. Overall, it is very unlikely that managed forests act as carbon sinks in the long run.
While the work is of interest, the article is rather difficult to follow and, in my opinion, lacks clarity. Please find below some specific comments.
Specific comments
L24–28: given the huge importance it will have throughout your paper, I suggest you define C sequestration and C storage here, so the difference between both is clear.
L35–37: these two sentences are unclear.
L38: circular definition; you define carbon sequestration by the carbon balance, which you define with the carbon sequestration.
L41: yes, a carbon sink is negative – if it is positive, then it is a source and not a sink. I would thus remove ‘negative’.
L69: please define NPV.
L74: how do they define ‘optimal harvest age’ in the paper you cite? Which criterion does optimal refer to?
L100–103: please check these sentences, I may be wrong but it seems redundant to me. If there is a nuance, please make it clearer.
L115: the question may be naive, I am not an expert of wood consumption: if your model were to be used at international level, do you think it would be important to use country-specific values for these half-lives? Do consumption patterns significantly vary from one country to another, which would make the results country-dependent? Also, are all these values (half-lives and Table 1) dependent on the tree species?
L130: please indicate once that RMB is ‘yuans’ (in the Table caption at least).
L140: to me, the figure 1 is unclear: are all the points results from simulation with the same parameters? Or from different scenarios? Instead of huge ellipses, perhaps you could indicate the thinning times with a line or arrow, it would be more precise.
L146–147: I don’t understand how you ‘predict the effect of thinning’ from this.
L149: is this the equation that governs the results in figure 1? If so, it should be presented before the figure.
L201: why does foliage have a negative age in Table 2? I understand it may come from the best fit for the model, but shouldn’t this (T > 0) be one of the constraints?
L244: you should indicate the thinnings clearly on the graphs. Also, what % does a thinning correspond to (regarding the wood density)?
Technical corrections
L166: maybe a typo, but there is no r in the formula.
Citation: https://doi.org/10.5194/egusphere-2026-4236-RC2 -
AC2: 'Reply on RC2', Xingji Jin, 08 Oct 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4236/egusphere-2026-4236-AC2-supplement.pdf
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AC2: 'Reply on RC2', Xingji Jin, 08 Oct 2026
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- 1
The manuscript focuses on effectively integrating carbon sequestration as an additional objective in Larix plantations in China using a single-criterion optimisation model. While some interesting results are presented, it is recommended that the manuscript not be published in its current form. My comments are provided below:
GENERAL COMMENTS:
Some very important assumptions underlying forest planning exercises have not been adequately explained and/or justified. One of these relates to the type of management associated with the case study. The rotation period used is derived from actual plantation data, even though the objective is based on a single criterion (timber only). Furthermore, the silvicultural approach considers only this provisioning ecosystem service. Why has an approach based on silviculture and a rotation period more appropriate to the carbon sequestration objective not been included? They are implicitly assuming that carbon does not influence the optimal rotation period to be applied in these plantations.While accounting for felling residues from the previous rotation is justified, one should also consider the emissions associated with timber products derived from final felling operations in the previous rotation. It is unclear whether this has been considered in this study. Ultimately, I believe it would be more useful to start and finish the analysis when the carbon contained in the products is re-emitted into the atmosphere, rather than at the rotation stage. Various variables and parameters have not been adequately justified, in addition to the points mentioned above. In short, anyone wishing to replicate the study would encounter difficulties.
MAJOR COMMENTS:
I think there should be a reference somewhere to the possibility of accounting for the carbon sequestered within a carbon market, whether compliance or regulated. It seems strange to discuss the carbon associated with forest plantations without considering the associated transaction costs and trading requirements. These constraints may justify modifying the silvicultural practices employed when only timber production is considered.
Justification should be provided for why the Olson (1963) model was chosen.
p. 161. The objective is to maximise the NPV, not to achieve three.
The discount rate used in Eq. 4 is not justified. It is particularly striking that they use a rate of 1 per cent here, whilst in Figure 4 they refer to a discount rate of 4 per cent. Clearly, given these facts, a reader cannot replicate the analysis.
l. 174, it is unclear whether subsidies/charges are applied annually and how this is incorporated into the optimisation model.
l. 196. The carbon price is not justified.
Tables 2 and 3. Neither table is easy for the reader to understand. Furthermore, it makes little sense to include negative values for T (age of the stand, according to the legend) without providing a proper explanation.
Discussion: I do not understand why a heading (4.1) has been included when there are none in the rest of the section. Similarly, it is striking that the limitations of the study, future directions and key conclusions have not been highlighted.
The concept of 'carbon-smart forestry' has not been adequately defined.
MINOR COMMENTS:
I do not understand the purpose of the red circles in Figure 1.
Figure 4 should not span two pages. As it stands, this makes the figure difficult to understand.