Subalpine grassland productivity increased with warmer and drier conditions, but not with higher N deposition, in an altitudinal transplantation experiment

Volk, Matthias; Suter, Matthias; Wahl, Anne-Lena; Bassin, Seraina

doi:https://doi.org/10.5194/bg-18-2075-2021

Articles | Volume 18, issue 6

https://doi.org/10.5194/bg-18-2075-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-18-2075-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 6

Research article

|

23 Mar 2021

Research article |

| 23 Mar 2021

Subalpine grassland productivity increased with warmer and drier conditions, but not with higher N deposition, in an altitudinal transplantation experiment

Matthias Volk, Matthias Suter, Anne-Lena Wahl, and Seraina Bassin

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Final revised paper (published on 23 Mar 2021)
Preprint (discussion started on 03 Sep 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'MS review', Anonymous Referee #1, 13 Oct 2020
- AC1: 'Comments by referee #1', Matthias Volk, 13 Oct 2020
  - RC2: 'response', Anonymous Referee #1, 13 Oct 2020
    - SC1: 'response', Matthias Volk, 14 Oct 2020
    - AC2: 'methods', Matthias Volk, 17 Nov 2020
- AC3: 'point by point response to RC1', Matthias Volk, 17 Nov 2020
RC3: 'The rising productivity of alpine grassland under warming, drought and N-deposition treatments', Anonymous Referee #2, 20 Oct 2020
- AC4: 'point by point response to RC3', Matthias Volk, 17 Nov 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (24 Nov 2020) by Sönke Zaehle

AR by Matthias Volk on behalf of the Authors (21 Dec 2020) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (04 Jan 2021) by Sönke Zaehle

RR by Anonymous Referee #1 (15 Jan 2021)

Suggestions for revision or reasons for rejection

Thanks to the authors for thoroughly and diligently responding to my comments and those of the other reviewer. In general I am satisfied with the revisions -- nice work! Below I list out the main points I made in my previous review and whether the authors addressed them acceptably, noting what if any revisions are still needed.

- Inclusion of description of plant species composition and photographs: Thanks for including species names and photographs; this is a big improvement.
- Issues with inference: I am glad to read that the management history of the different sites does not differ. It is also better that the title and framing of the study, based on changes suggested by the other reviewer, now reflect that this is an altitudinal transplant, with all that entails, and not necessarily a warming treatment. However I strongly object to the statement: "We regard this element of heterogeneity as an advantage, as it is a factor that supports the general applicability of our results." It is at best neutral and at worst a diluting influence on the applicability of the results because it introduces unwanted confounding variation. However I think this statement was only made in the response to the reviewers and not the main text. If such a statement is in the main text I would suggest removing it.
- Reproducibility: Thank you for depositing the data on Dryad, and providing the R code. I am glad that your analysis is now reproducible.
- Broader significance of study in abstract: I think the added sentences are helpful in establshing motivation and significance of the study.
- Discussion of factorial experiments: This is improved but I do not quite follow the logic in lines 127-130: (These findings suggest that the outcome of a global change productivity-experiment depends to some degree on the chosen treatment levels and their interaction with the ambient climate during the experiment. Combining multiple treatments with many levels might thus improve interpretation of experimental outcomes and related climate change predictions.) Please clarify.
- Justification of hypotheses: Thanks for this clarification.
- Explanation of choosing southern-exposed sites: Thanks for this clarification.
- Justification for thresholds: Thanks for this clarification.
- Explanation of how fixed vs. random effects were determined: I think this was a misunderstanding on my part; thanks for clarifying.
- Details of GAM fitting: Thanks for this clarification. I would suggest including this additional detail in the appropriate place in the methods section, or alternatively include your verbal clarification that you gave in the response document in the appendix (in addition to the code). It cannot hurt to be explicit.
- Clarification of discussion paragraph: Thanks for this clarification.
- Justification of statement that subalpine grassland productivity will increase with warming: I think the final statement of the concluding paragraph is still not fully supported by the data. I think the other reviewer made a similar point. Please reword this to be more suitable to the results you found.

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ED: Publish subject to minor revisions (review by editor) (25 Jan 2021) by Sönke Zaehle

AR by Matthias Volk on behalf of the Authors (27 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (29 Jan 2021) by Sönke Zaehle

Short summary

Grassland ecosystem services like forage production and greenhouse gas storage in the soil depend on plant growth. In an experiment in the mountains with warming treatments, we found that despite dwindling soil water content, the grassland growth increased with up to +1.3 °C warming (annual mean) compared to present temperatures. Even at +2.4 °C the growth was still larger than at the reference site. This suggests that plant growth will increase due to global warming in the near future.