Review of “Improving Permafrost Soil Representation in a Dynamic Global Vegetation Model Enhances Predictions of Boreal Forest Carbon Dynamics and Vegetation Structure” by Yang et al.

General comments

In this manuscript, the authors present a refined vertical soil structure in the LPJ-GUESS-Cryo model, which improves the simulation of aboveground biomass and NPP compared to remote sensing estimates within the study region. The paper falls within the journal's scope and addresses a relevant topic: the representation of permafrost-related processes in global vegetation models.

However, the manuscript would benefit from a more detailed discussion on the choice of development approach. While the model improvements are clearly described and shown to enhance performance, the rationale behind methodological choices remains insufficiently explored.

In addition, the analysis did not address potential impacts on soil carbon storage and permafrost carbon emissions from changes in soil hydrothermal dynamics. Providing a more thorough analysis of the methodological choices and their implications - also for belowground processes and on a regional scale - would substantially strengthen the manuscript.

Specific comments

Title: The authors could consider specifying their study region (e.g. boreal forests of Northeast China) to mark that their developments have been tested on a site scale

Figure 1. Please edit the caption, so that it is self-explanatory, e.g. Study area location in Heilongjiang Province and the Inner Mongolia Autonomous Region (left) and land use classification based on X (right).

Table B1-B2. Please add the abbreviations (e.g. MAE) in the table header.

L50: Consider elaborating on (1) why simplified representations are commonly used in DGVMs, and (2) which specific processes limit their ability to simulate cold-region soil hydrothermal dynamics realistically.

L55: Please clarify what is meant by “high climate sensitivity” and “extensive forest cover,” and explain why these characteristics make the study region particularly suitable.

L76: rephrase: the regions has high vegetation cover…

L90. Permafrost and wetland-related processes had been implemented in LPJ-GUESS based on Wania et al 2009a, 2009b (https://doi.org/10.1029/2008GB003412, https://doi.org/10.1029/2008GB003413).

L214. Please rephrase for clarity. e.g. Larger Δ value indicated larger differences between LPJ-GUESS and LPJ-GUESS-Cryo.

L217. What do you mean by “joint hydrothermal perturbations”?

L380. Regarding study limitations: In addition to their impact on soil thermohydrodynamics, it would be interesting to at least mention how these developments affect simulated carbon balance in these permafrost-underlain areas. It would be important to emphasize that although improving the vertical thermodynamics is important, models in general still lack other processes (e.g. vertical soil carbon storage) that challenge the accuracy of simulated vegetation dynamics and carbon fluxes in permafrost underlain regions.

Additionally, the developments would still need to be tested on a broad regional scale (e.g. Pan-Arctic), to ensure the robustness of improvement in soil temperature and carbon balance estimates.  

L420. While the authors correctly highlight the importance of improving soil hydrothermal processes, it would be helpful to clarify that the presented developments represent a step forward rather than a comprehensive solution.

Technical corrections

L7: rephrase: e.g. Our model evaluation shows…

L63: Materials and Methods

L64: Study area

L184. Structural changes

L187: made to the model

L241: repeated sentence

L310: “conditions(Gert”