Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-643
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Technical note
13 Jan 2017
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Technical note: An experimental setup to measure latent and sensible heat fluxes from (artificial) plant leaves
Stanislaus J. Schymanski, Daniel Breitenstein, and Dani Or Department of Environmental Sciences, ETH Zurich, 8092 Zurich, Switzerland
Abstract. Leaf transpiration and energy exchange are coupled processes that operate at small scales yet exert a significant influence on terrestrial hydrological cycle and climate. Surprisingly, experimental capabilities required for quantifying the energy-transpiration coupling at the leaf scale are lacking, challenging our ability to test basic questions of importance for resolving large scale processes. The present study describes an experimental setup for the simultaneous observation of transpiration rates and all leaf energy balance components under controlled conditions, using an insulated closed-loop miniature wind tunnel and artificial leaves with pre-defined and constant diffusive conductance for water vapour. A range of tests documents the above capabilities of the experimental setup and points to potential improvements. The tests reveal a conceptual flaw in the assumption that leaf temperature can be characterised by a single value, suggesting that even for thin, planar leaves, a temperature gradient between the irradiated and shaded or transpiring and non-transpiring leaf side can lead to bias when using observed leaf temperatures and fluxes to deduce effective conductances to sensible heat or water vapour transfer. However, comparison of experimental results with an explicit leaf energy balance model revealed only minor effect on simulated leaf energy exchange rates by the neglect of cross-sectional leaf temperature gradients, lending experimental support to our current understanding of leaf gas and energy exchange processes.

Citation: Schymanski, S. J., Breitenstein, D., and Or, D.: Technical note: An experimental setup to measure latent and sensible heat fluxes from (artificial) plant leaves, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-643, in review, 2017.
Stanislaus J. Schymanski et al.
Stanislaus J. Schymanski et al.

Data sets

Data and code to reproduce computational results and plots
S. Schymanski
doi:10.5281/zenodo.241217
Stanislaus J. Schymanski et al.

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Short summary
Leaf transpiration and energy exchange are coupled processes at the small scale that have strong effects on the water cycle and climate at the large scale. In this technical note, we present a novel experimental setup that enables detailed study of these coupled processes in the laboratory under controlled conditions. Results document the capabilities of the experimental setup to confirm or challenge our understanding of these processes.
Leaf transpiration and energy exchange are coupled processes at the small scale that have strong...
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