Using models to guide field experiments: a priori predictions for the CO2 response of a nutrient‐ and water‐limited native Eucalypt woodland |
| |
Authors: | 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 |
| |
Affiliation: | 1. Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia;2. Department of Biological Sciences, Macquarie University, North Ryde, NSW, Australia;3. Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Jena, Germany;4. Oak Ridge National Laboratory, Environmental Sciences Division and Climate Change Science Institute, Oak Ridge, TN, USA;5. Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden;6. CSIRO Oceans and Atmosphere Flagship, Aspendale, Vic., Australia;7. ISPA, Bordeaux Science Agro, INRA, Villenave d'Ornon, France |
| |
Abstract: | 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. |
| |
Keywords: | carbon dioxide drought ecosystem model
Eucalyptus tereticornis
phosphorus |
|
|