Dear Dr. Klinge,

first of all, I apologize for the delay of the review process and acknowledge the two referees for providing the reviews. After carefully reading their reports and your responses how you will address the reviewer's comments, critics and suggestions, I decided to consider bg-2017-220 for publication in Biogeosciences after a major revision. However, it would be helpful if you could provide a marked-up manuscript version (track changes in Word) converted into a pdf-file including the author's response.

Both reviewers indicated, that the term "ecozone" is not appropriate for small-scale units and should be changed throughout the manuscript. Please also consider the rewording of other terms as pointed out by both reviewers.

Furthermore, the authors should provide more information on treeline ecology and dynamics triggered by climate and anthropogenic changes.

Minor corrections indicated by reviewer 1 should be considered in the revision of bg-2017-220 (at line 85 there is no comma after "et al." in the in-text citation).

As indicated by reviewer 2 the authors should strengthen the manuscript avoiding repetitions and reorganize the sequence of figures.

A revision of the English language by a native speaker is important, as Biogeosciences does not provide this service during the editing process.

I suggest to shift figure 6 to the supplementary information.

As indicated by reviewer 2 the authors should refer to the accuracy and quality of the used climate data sets indicating the literature of peer-reviewed publications which validated these data sets. I appreciate the suggestion of the authors to present more additional information on climate data and the indicated figures in the author's response should be included in the supplementary material, however, explicitly explained in the figure legends and improving the quality of figure 3 (units and scales of axes are difficult to read). Please indicate clearly in figure 1 the periods of both precipitation datasets, PRISM and CHELSA and present both figures at the same scale. Please indicate coordinates for figures 1 and 2.

Further comments of reviewers 1 and 2 should be addressed in the revised version of bg-2017-220.

Best regards,
Jochen Schöngart
(Associated Editor of Biogeosciences)

Dear Michael Klinge,

I passed through the revision of bg-2017-220. The manuscript improved considerably after your revision and is more fluent in reading. Still some technical corrections should be performed before the manuscript can be published in Biogeosciences.
Thank you for Biogeosciences to publish this interesting study and my apologizes for the long review period.

Best regards,
Jochen Schöngart
(Associated Editor of Biogeosciences)

Affiliations:
L. 5-10: Please make consistent use of German umlauts (ä, ö, ü)

Abstract:
L. 20/21: Sentence ends and the following sentence starts with “forest distribution”, please alter this.
L. 42/43: The mean growing season temperature (MGST) of 7.9-42 8.9 °C and a minimum MGST of 6 °C are limiting parameters at the 43 upper treeline but are negligible for the lower treeline.
L. 54: Delete comma after “taiga”

Introduction:
L. 80/81: …whereas the steppes are part of the Mongolian-Chinese steppe region (please rephrase sentence)
L. 89: …2003?
L. 129: Delete “the” before “tree growth”
L. 163: Batima et al., (2005) (please delete comma after “et al.”)
L. 176: Please add a comma after “seasons”
L. 203: “was” instead of “is”

Study Area:
L. 251: Larix sibirica
L. 266: Are these several species of Populus? If yes, please indicate Populus spp.

Methods:
L. 323: please use “En dashes” for ranges (1999–2013)

Results:
L. 381: Please correct cited reference
L. 392: …Klinge et al. (2003),…
L. 408: Please add a dot at the end of the sentence
L. 448: Please initiate the sentence with the full word “Figure”
L. 476: Please insert a comma before “but”
L. 482: Does instead of do (refers to relation)
L. 487: Please use “En dashes” for ranges (0.44–0.71)
L. 505: Please insert a comma before “but”
L. 516: indicates (refers to correlation)

Discussion:
L. 587 and 592: Please use “En dashes” for ranges (6–8)
L. 600: What are “dark” taiga tree species? Conifers?

Conclusion
L. 627: differs (refer to distribution)
L. 643: Please insert a comma before “but”
L. 664: mean (refer to forest dynamics and forest development)
Acknowledgement
L. 672: Please add a comma after “Belgium”

Figure legends:
L. 706: Gunin and Vostokova (2005)
L. 713 and 725: Please use “En dashes” for ranges
L. 717-719: please also indicate the meaning of a.s.l.

Supplementary information:
L: 737: WorldClim; please use “En dashes” for ranges
L. 748: Indicate a dot at the end of the sentence
Figure S3: “Pinus sibirica” in the figure’s legend.

References:
Please sort multiple citations of Dulamsuren et al. and Klinge et al. in chronological order (see guidelines for authors)

Numbers: Please make consistent use of the formats for decimal numbers (dot as separator) and those over 1000 (comma) in text, figures and tables