Identification of key parameters controlling demographically structured vegetation dynamics in a land surface model: CLM4.5(FATES)

Massoud, Elias C.; Xu, Chonggang; Fisher, Rosie A.; Knox, Ryan G.; Walker, Anthony P.; Serbin, Shawn P.; Christoffersen, Bradley O.; Holm, Jennifer A.; Kueppers, Lara M.; Ricciuto, Daniel M.; Wei, Liang; Johnson, Daniel J.; Chambers, Jeffrey Q.; Koven, Charlie D.; McDowell, Nate G.; Vrugt, Jasper A.

doi:https://doi.org/10.5194/gmd-12-4133-2019

Articles | Volume 12, issue 9

https://doi.org/10.5194/gmd-12-4133-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-12-4133-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 9

Development and technical paper

|

23 Sep 2019

Development and technical paper |

| 23 Sep 2019

Identification of key parameters controlling demographically structured vegetation dynamics in a land surface model: CLM4.5(FATES)

Elias C. Massoud, Chonggang Xu, Rosie A. Fisher, Ryan G. Knox, Anthony P. Walker, Shawn P. Serbin, Bradley O. Christoffersen, Jennifer A. Holm, Lara M. Kueppers, Daniel M. Ricciuto, Liang Wei, Daniel J. Johnson, Jeffrey Q. Chambers, Charlie D. Koven, Nate G. McDowell, and Jasper A. Vrugt

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Final revised paper (published on 23 Sep 2019)
Preprint (discussion started on 07 Feb 2019)

Interactive discussion

Status: closed

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

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- Supplement

SC1: 'Interactive Comments on Sensitivity Analyses', Vick Prasad, 13 Feb 2019
- SC2: 'Quick response Vick Prasad', Chonggang Xu, 15 Feb 2019
- AC1: 'Final response', Chonggang Xu, 28 May 2019
RC1: 'Review', Nancy Kiang, 22 Feb 2019
- AC1: 'Final response', Chonggang Xu, 28 May 2019
RC2: 'Review', Xiangtao Xu, 23 Feb 2019
- AC1: 'Final response', Chonggang Xu, 28 May 2019
RC3: 'Review', Sebastian Lienert, 04 Mar 2019
- AC1: 'Final response', Chonggang Xu, 28 May 2019
AC1: 'Final response', Chonggang Xu, 28 May 2019

Peer-review completion

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

AR by Anna Wenzel on behalf of the Authors (01 Jul 2019) Author's response

ED: Referee Nomination & Report Request started (05 Jul 2019) by Christoph Müller

RR by Xiangtao Xu (15 Jul 2019)

Suggestions for revision or reasons for rejection

I am generally happy with the revision. It helps to improve the manuscript by a lot. The correlation analysis between climate forcing and sensitivity indices are helpful and make sense. The re-organization of figures improves readability. My only suggestion is to connect such kind of computational sensitivity analysis with theoretical ecological analysis in vegetation demography in the Conclusion part. The FAST method presented here can provide a more comprehensive analysis of the parameters that control vegetation demography while simpler but more tractable theoretical ecology models (e.g. Farrior et al. 2016 and Falster et al. 2018) can provide more mechanistic understanding (e.g. why and how allometry influences demography). Such modeling exercises at different scales and complexity are complementary, especially when vegetation models are getting more and more complex nowadays.

Farrior, C.E., Bohlman, S.A., Hubbell, S. & Pacala, S.W. (2016) Dominance of the suppressed: Power-law size structure in tropical forests. Science, 351, 155–157.
Falster, D.S., Duursma, R.A. & FitzJohn, R.G. (2018) How functional traits influence plant growth and shade tolerance across the life cycle. Proceedings of the National Academy of Sciences, 115, E6789–E6798.

In addition, Page 19 Line 1-5 discussed the model-data comparison for mortality. My understanding is that the authors extracted and averaged instantaneous mortality in the model, which is calculated differently from the census-based mortality. For example, if all the trees of a given size class died within a 10-year census, the mortality from the observation would be 0.1 per year although they might have already died in the first few years (i.e. actual mortality is higher). So I am not so surprised at the modeled mortality for small trees is higher than the observed because they are at different time scales. An apple-to-apple comparison should simulate census processes in the model as well, which involves tracking cohorts in the model. This is definitely too much for this manuscript but it is worthy of mentioning in the discussion to avoid confusion.

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ED: Publish subject to minor revisions (review by editor) (30 Jul 2019) by Christoph Müller

AR by Chonggang Xu on behalf of the Authors (09 Aug 2019) Author's response Manuscript

ED: Publish as is (16 Aug 2019) by Christoph Müller

AR by Chonggang Xu on behalf of the Authors (16 Aug 2019) Author's response Manuscript

Short summary

We conducted a comprehensive sensitivity analysis to understand behaviors of a demographic vegetation model within a land surface model. By running the model 5000 times with changing input parameter values, we found that (1) the photosynthetic capacity controls carbon fluxes, (2) the allometry is important for tree growth, and (3) the targeted carbon storage is important for tree survival. These results can provide guidance on improved model parameterization for a better fit to observations.