Please address the comments of both reviewers.

The initial reviews of your manuscript suggested major revisions and both reviewers pointed to the problem that there is no time control on your samples. Do your samples represent less than one year or more than 1/2 a century? There is no way to determine this without 14C analyzes. You have not adequately addressed these concerns. I sent your ms back to the reviewer #2 and the reviewer suggested to reject your ms based on the lack of time control. I agree with this; without time constraint you don't understand what you've measured, nor what is responsible for the d13C change. I recommend to analyze at least some samples for 14C to constrain the time your samples represent and then resubmit your manuscript.

Please comment on the reviewer's critiques and add discussion to your manuscript regarding the issue of time constraint on your samples pointed out by both reviewers. How can we be certain that your samples average similar time periods? How can we know if the trees grow faster or slower in these different environments and you are merely time averaging different periods with different atmospheric CO2 d13C values and/or WUE? The ~2 per mil range you see in your samples has been recorded within the stem of a single tree in both tropical and temperate environments, so your results might be explained from time averaging different periods (See Helle & Schleser 2004 Plant Cell and Environment 27 367–380; and Verheyden et al. 2004 Plant Cell and Environment 27 1525–1536). I suggest adding an entire new section to the discussion about the issue of time constraint of your samples - one argument you could use is that one would expect growth rate to correlate with DBH (larger trees typically grow slower) and there is no correlation between d13C and DBH. But this still does not completely rule out variations in growth and thus time. I would also add a note that future studies should do high resolution analyses (see previously noted refs for example). In the ms you note that soil type was recorded, but I don't see this anywhere - could soil type play a role in WUE and influence your data?

The data are certainly interesting, but are not perfect. Overall you need to tone down the confidence of your conclusions and open the possibility of the time time averaging issue discussed above (as well as the other issues such as WUE differences or below/above canopy crowns). Without real time constraint on your samples, you cannot be certain about time averaging, and this uncertainty needs to be reflected in the ms. Discussing the limitations of your data will make this a more valuable contribution. I look forward to seeing your revised ms.

Please see the comments from both reviewers and revise your manuscript accordingly. They provide excellent comments that will improve your ms.

Thank you for your revisions- I feel the ms is now ready for publication. The manuscript is an excellent contribution to BG!