In the manuscript “Projected changes in land carbon store over the 21st century: what contributions from land-use change and atmospheric nitrogen deposition?”, the authors evaluated the changes of CLCS projections in SSPs, focusing the uncertainties from land use change and nitrogen deposition. The authors concluded that the projection spread contributed by land use change spread is larger than from CO2 spread, and the nitrogen deposition has relatively smaller contribution. This conclusion is important and has significant implications for understanding the projections of the Earth system models. However, I think the presentation of this manuscript need to be improved and a few concerns need to be addressed before publishing.

The main concern I have is about the land use change and N deposition spread. The authors “used the selected SSP markers spread as a proxy for the inter-IAM spread”. Although the authors compared the two spreads, and showed them to have similar magnitude. There is still possibility that the differences of vegetation types are systematically different among SSP markers and IAMs. i.e. the SSP markers spread could come from the scenario differences while inter-IAM spread for the same scenario is from model differences. The same vegetation type distributed in different regions (e.g. tropical and boreal forests) may have different C source/sink. Therefore, besides the global analyses, it is necessary to check where the differences are in SSP markers spread and inter-IAM spread.

Also, I think the authors need to carefully use the term “uncertainty”. In my opinion, the forcings are from different scenarios and the differences due to the forcings are thus not something “uncertain” but some “certain” signal. The use of “spread” is also somehow inaccurate as we usually use the term for “model spread”. I prefer to explain the results as scenario difference rather than “uncertainty”.

My second concern is that this study is based on a single model ORCHIDEE-v3. Given the large differences among land surface models, I wonder how robust the results are. I am not asking to add new simulations, but discussing this uncertainty is helpful. The authors may compare ORCHIDEE-v3 and other models’ performances in the TENDY land use change experiments to estimate the robustness of this study.

Finally, I suggest the authors to divide Section 3 into subsections, so the readers can better follow and capture the key points.

Line 57: non-makers -> non-markers

I have attached my review as a PDF for the convenience of authors.