Community-specific hydraulic conductance potential of soil water decomposed for two Alpine grasslands by small-scale lysimetry

Frenck, Georg; Leitinger, Georg; Obojes, Nikolaus; Hofmann, Magdalena; Newesely, Christian; Deutschmann, Mario; Tappeiner, Ulrike; Tasser, Erich

doi:https://doi.org/10.5194/bg-15-1065-2018

Articles | Volume 15, issue 4

https://doi.org/10.5194/bg-15-1065-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-15-1065-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 4

Research article

|

21 Feb 2018

Research article |

| 21 Feb 2018

Community-specific hydraulic conductance potential of soil water decomposed for two Alpine grasslands by small-scale lysimetry

Georg Frenck, Georg Leitinger, Nikolaus Obojes, Magdalena Hofmann, Christian Newesely, Mario Deutschmann, Ulrike Tappeiner, and Erich Tasser

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Final revised paper (published on 21 Feb 2018)
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Preprint (discussion started on 07 Jul 2017)

Interactive discussion

Status: closed

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

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RC1: 'Referee comment on bg-2017-253', Anonymous Referee #1, 01 Aug 2017
- AC1: 'Response to reviewer 1', Erich Tasser, 27 Sep 2017
RC2: 'Evapotrasnpiration in two contrasted Alpine pasture communities (wet vs mesic) under two contrasted rainfall regimes', Anonymous Referee #2, 30 Aug 2017
- AC2: 'response to reviewer 2', Erich Tasser, 27 Sep 2017

Peer-review completion

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

ED: Reconsider after major revisions (29 Sep 2017) by Paul Stoy

AR by Erich Tasser on behalf of the Authors (10 Nov 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Nov 2017) by Paul Stoy

RR by Anonymous Referee #1 (10 Dec 2017)

RR by Anonymous Referee #3 (13 Dec 2017)

Suggestions for revision or reasons for rejection

Frenck and others measure water use and biomass gain by alpine plant communities from mesic and more xeric sites. Plants from the xeric sites exhibit a ‘water savings’ strategy.

I found the technical aspects of the analysis to be interesting but the authors seem to have missed recent literature on isohydricity/anisohydricity (see e.g. http://onlinelibrary.wiley.com/doi/10.1111/gcb.13389/full). Opportunities to place observations in the context of surface and stomatal conductance were missed, and the results are therefore rather qualitative with respect to ‘more water savings vs. more water spending’. The manuscript has interesting elements, but at a minimum the following comments must be integrated and the role of surface conductance and plant strategy discussed to place the manuscript into a more modern (with respect to the literature) context.

‘merely understood’ on line 35 doesn’t make sense. Poorly understood? And if so, why?

The abstract didn’t contain a single number and was entirely qualitative. Please re-write to add quantitative vigor to the abstract.

On 65, the Jasechko et al. 2013 study has been roundly criticized by other studies. Basically it is incorrect. I recommend taking a look at the following references:

Coenders-Gerrits, A. M. J., Van der Ent, R. J., Bogaard, T. A., Wang-Erlandsson, L., Hrachowitz, M. and Savenije, H. H. G.: Uncertainties in transpiration estimates, Nature, 506(7487), E1–E2, 2014.
Fatichi, S. and Pappas, C.: Constrained variability of modeled T:ET ratio across biomes, Geophys. Res. Lett., 2017GL074041, doi:10.1002/2017GL074041, 2017.
Schlaepfer, D. R., Ewers, B. E., Shuman, B. N., Williams, D. G., Frank, J. M., Massman, W. J. and Lauenroth, W. K.: Terrestrial water fluxes dominated by transpiration: Comment, Ecosphere, 5(5), 1–9, doi:10.1890/ES13-00391.1, 2014.
Schlesinger, W. H. and Jasechko, S.: Transpiration in the global water cycle, Agric. For. Meteorol., 189, 115–117, 2014.
Wang, L., Good, S. P. and Caylor, K. K.: Global synthesis of vegetation control on evapotranspiration partitioning, Geophys. Res. Lett., 41(19), 6753–6757, doi:10.1002/2014GL061439, 2014.
Wei, Z., Yoshimura, K., Wang, L., Miralles, D. G., Jasechko, S. and Lee, X.: Revisiting the contribution of transpiration to global terrestrial evapotranspiration, Geophys. Res. Lett., 44(6), 2792–2801, doi:10.1002/2016GL072235, 2017.

On 108 please quantify what is meant by ‘past’ by van der Schrier et al., 2007. The past few millennia?

Line 126-7 should be re-worded.

I agree with previous reviews with respect to the use of “common garden” in this case (line 150). It isn’t strictly a common garden experiment.

On 160, the hypothesis is a straw man. This is how vegetation works by “spending” water when it is available and a “sudden decline” near the wilting point! The question is how (quantitatively) transpiration remains high amongst different vegetation types. That being said, does ‘continuous’ mean ‘monotonically decreasing’? There will be a point in the soil moisture continuum in which transpiration is insensitive to soil moisture.

The methods seem largely sound given the challenges of lysimeter measurements. The soil hydraulic parameter determination is exemplary, as are the uncertainty estimates.
Points representing actual measurements in Fig. 4 would help the reader understand the trends and uncertainties (as in Fig. 5).

Please don’t use the comma on line 501 and elsewhere to denote the decimal point (see Fig. 6B).

The ‘component, which defines ecosystem water flux beyond the impact of variations in total biomass’ is stomatal regulation on line 573. I found it perhaps somewhat surprising that surface or canopy conductance variations along the soil moisture trajectories weren’t estimated given its central role in plant and ecosystem physiology. Is this ‘water savings’ vs. ‘water spending’ strategy related to plant isohydricity/anisoydricity?

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ED: Publish subject to minor revisions (review by editor) (13 Dec 2017) by Paul Stoy

AR by Erich Tasser on behalf of the Authors (22 Dec 2017)

ED: Publish as is (15 Jan 2018) by Paul Stoy

AR by Erich Tasser on behalf of the Authors (16 Jan 2018)

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Short summary

For central Europe in addition to rising temperatures, an increasing variability in precipitation is predicted. In a replicated mesocosm experiment we compared evapotranspiration and the biomass productivity of two differently drought-adapted vegetation communities during two irrigation regimes (with and without drought periods). Significant differences between the different communities were found in the response to variations in the water supply and biomass production.