Dear authors,

please provide a revised version with a point-by-point explanation on how you have adjusted the manuscript with respect to the reviewer comments.

Best wishes,
Sönke

Dear authors,
many thanks for your thoroughly revised manuscript, which I find now suitable for publication in Biogeosciences. I have a small range of editorial remarks, which I ask you to address before final acceptance:

- add "daily" in the LPX-Bern description: Adt is a function of DAILY radiation, ... (pge 8, ~line 27)

- in the results section, and the added text regarding the soil moisture effect on WUE, where you describe the added experiment with constant climate. Please be specific as to whether constant climate includes constant CO2 or not. (page 19, line 9)

- please remove the eq in page 24 line 16. The reference to eq 7 is sufficient.

- please cut the sentence beginning page 25 line11 (In brief,...) into smaller bits.

- page 27 l 12: There is a striking difference between the results of De Kauwe et al. 2013 and Battipaglia et al. 2013 in terms of the iWUE response under elevated
CO2 although they are based +/- on the same sites. I currently don't know why, but I think it would be good to highlight that there is a difference between the observed leaf level and tree-ring response that still deserves discussion (rather than just treating these values as independent...).

IMHO the following sentences from the conclusion are not necessary: "The implementation of 13C and isotopic discrimination during photosynthesis
in the Community Land Model (CLM4.5) and in the LPX-Bern (version 1.3) is documented. Results from isotope-enabled
simulations compared to the tree ring reconstructions as well as to a published compilation of δ13C of leaf material. "