Using models to guide field experiments: a priori predictions for the CO2 response of a nutrient- and water-limited native Eucalypt woodland

Belinda E. Medlyn, Martin G. De Kauwe, Sönke Zaehle, Anthony P. Walker, Remko A. Duursma, Kristina Luus, Mikhail Mishurov, Bernard Pak, Benjamin Smith, Ying-Ping Wang, Xiaojuan Yang, Kristine Y. Crous, John E. Drake, Teresa E. Gimeno, Catriona A. Macdonald, Richard J. Norby, Sally A. Power, Mark G. Tjoelker, David S. Ellsworth

    Research output: Contribution to journalArticlepeer-review

    67 Citations (Scopus)


    The response of terrestrial ecosystems to rising atmospheric CO2 concentration (Ca ), particularly under nutrient-limited conditions, is a major uncertainty in Earth System models. The Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodland presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. We applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experiments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluate data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercomparison. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low-rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth; feedbacks to nutrient uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements.

    Original languageEnglish
    Pages (from-to)2834-2851
    Number of pages18
    JournalGlobal Change Biology
    Issue number8
    Publication statusPublished - Aug 2016


    • carbon dioxide
    • drought
    • ecosystem model
    • Eucalyptus tereticornis
    • phosphorus


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