Optimal plant water-use strategies under stochastic rainfall

Authors

  • Stefano Manzoni,

    Corresponding author
    1. Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden
    2. Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
    3. Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
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  • Giulia Vico,

    1. Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
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  • Gabriel Katul,

    1. Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
    2. Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA
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  • Sari Palmroth,

    1. Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
    2. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
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  • Amilcare Porporato

    1. Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
    2. Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA
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Abstract

Plant hydraulic traits have been conjectured to be coordinated, thereby providing plants with a balanced hydraulic system that protects them from cavitation while allowing an efficient transport of water necessary for photosynthesis. In particular, observations suggest correlations between the water potentials at which xylem cavitation impairs water movement and the one at stomatal closure, and between maximum xylem and stomatal conductances, begging the question as to whether such coordination emerges as an optimal water-use strategy under unpredictable rainfall. Here mean transpiration <E> is used as a proxy for long-term plant fitness and its variations as a function of the water potentials at 50% loss of stem conductivity due to cavitation and at 90% stomatal closure are explored. It is shown that coordination between these hydraulic traits is necessary to maximize <E>, with rainfall patterns altering the optimal range of trait values. In contrast, coordination between ecosystem-level conductances appears not necessary to maximize <E>. The optimal trait ranges are wider under drier than under mesic conditions, suggesting that in semiarid systems different water use strategies may be equally successful. Comparison with observations across species from a range of ecosystems confirms model predictions, indicating that the coordinated functioning of plant organs might indeed emerge from an optimal response to rainfall variability.

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