the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Technical note: Common ambiguities in plant hydraulics
- 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
- 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
- 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
- 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
Abstract. Plant hydraulics gains increasing interest in plant eco-physiology and vegetation modeling. However, the hydraulic properties and profiles are often improperly represented thus leading to biased results and simulations, e.g., the neglection of gravitational pressure drop results in overestimated water flux. We highlight the commonly seen ambiguities and/or misunderstandings in plant hydraulics, including (1) distinction between water potential and pressure, (2) differences among hydraulic conductance and conductivity, (3) xylem vulnerability curve formulations, (4) stomatal model representations, (5) bias from analytic estimations, (6) whole plant vulnerability, and (7) neglected temperature dependencies. We recommend careful thinking before using or modifying existing definitions, methods, and models.
Yujie Wang and Christian Frankenberg
Status: open (until 17 Jun 2022)
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RC1: 'Comment on bg-2022-96', Anonymous Referee #1, 15 May 2022
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The technical note from Yujie Wang and Christian Frankenberg focuses on still very poorly investigated area of modern plant ecology and hydrology focusing on describing and parameterizing the plant hydraulic properties as key parameters for simulation of plant or canopy transpiration and/or water uptake.
The paper is well written and can be interesting for modelers of plant hydrology to parameterize the transpiration and water transport in plant communities. The manuscript is in scope of J. Biogeoscience and can be publish in the journal after some revision.
Actually, I guess a few points have to be additionally discussed in the paper.
- All tall plant and trees are characterized by a non steady-state water transport through the soil - root- stem -branch - atmosphere system, i.e. the water fluxes at different plant segments is different e.g. root water uptake is not equal transpiration at some short time intervals. Plant tissue and leaves accumulate water which can later be used for transpiration...
- Xylems of woody plants are very heterogeneous and characterized by different hydraulic conductance (for example along radial profile). Ignoring such effect can result in biased model results.
- One of a key objectives of your study is to "highlight the commonly seen ambiguities and/or misunderstandings in plant hydraulics" including different sections and particularly the "(4) stomatal model representations". Unfortunately this section is very poorly discussed in the manuscript.
Specific comments.
"The risk of stomatal opening" is not the best term for the sentence from ecological point of view. Stomatal opening and closing are very important physiological processes in plants. It is better to use the term e.g. "stomatal response", "stomatal functioning", or any. So, I suggest to reformulate the sentence.
Yujie Wang and Christian Frankenberg
Yujie Wang and Christian Frankenberg
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