Dear authors,

many thanks for your responses. Please submit a suitably revised manuscript taking on board these responses and provide a point-to-point letter explaining how you have changed the manuscript.

Concerning my unclear remark: If the spin-up period was not included in the assimilation, then the initial state of the ecosystem corresponds - for any run in the assimilation period - always to the prior simulation. If the assimilation procedure changes amongst others the carbon influx into the ecosystem, such a scheme means that this does not affect the stocks of carbon in the ecosystem, therefore the resulting net carbon balance will not be only a result of the assimilation procedure, but also depend on the prior simulations. I was unsure from reading your manuscript, how you have dealt with this issue, and any clarification/discussion would be appreciated.

Best,
Sönke Zaehle

Dear authors,

many thanks for your revisions, which have largely addressed the reviewer comments. I still think that the discussion is not very deep, but since there is a longer review of previous work now in the introduction and the limits of the study are clearly outlined, I believe that this is still acceptable. I nevertheless have a range of minor editorial points that I would like you to address before this manuscript can finally be accepted for publication.

Best wishes,
Sönke

Minor comments:

Abstract:
- not clear what the NEE sum is. Do you mean to say annual NEE?
- sentence beginning with "Thus, the parameter estimates would". This sentence seems redundant to me with the previous sentence. In any case, I don't understand the use of would here, either the new parameters change the carbon balance, as was said before, or they do not, but given your results, there should be a clear answer.
- sentence beginning with "The increase of sigma_sum_NEE" is hard to understand. Either revise to be clear ("substantially lower than for crops") or remove.

introduction
P2 L2 NEE is the difference between soil AND PLANT respiration and photosynthetic CO2 uptake
P2 L17: use affect instead of determine (there are other factors as well)
P2 L21: Is Todd-Brown et al. 2013, which evaluates soil carbon stocks in ESMs really a good reference to suggest that the phenology of LSMs is flawed?
P4 L23: remove duplicate ','