title: Using models to guide field experiments: a priori predictions for the CO2 response of a nutrient- and water-limited native Eucalypt woodland.
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.
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.|Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia.
authors.forename: Belinda E
authors.identifier: 0000-0001-5728-9827
authors.initials: BE
authors.lastname: Medlyn
authors.affiliation: Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia.
authors.forename: Martin G
authors.initials: MG
authors.lastname: De Kauwe
authors.affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.
authors.forename: Sönke
authors.initials: S
authors.lastname: Zaehle
authors.affiliation: Oak Ridge National Laboratory, Environmental Sciences Division and Climate Change Science Institute, 1 Bethel Valley Road, Oak Ridge, TN, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Walker
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Remko A
authors.identifier: 0000-0002-8499-5580
authors.initials: RA
authors.lastname: Duursma
authors.affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Luus
authors.affiliation: Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 22362, Lund, Sweden.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Mishurov
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, Private Bag 1, Aspendale, Vic., 3195, Australia.
authors.forename: Bernard
authors.initials: B
authors.lastname: Pak
authors.affiliation: Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 22362, Lund, Sweden.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Smith
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, Private Bag 1, Aspendale, Vic., 3195, Australia.
authors.forename: Ying-Ping
authors.initials: YP
authors.lastname: Wang
authors.affiliation: Oak Ridge National Laboratory, Environmental Sciences Division and Climate Change Science Institute, 1 Bethel Valley Road, Oak Ridge, TN, USA.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Kristine Y
authors.initials: KY
authors.lastname: Crous
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: John E
authors.initials: JE
authors.lastname: Drake
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.|ISPA, Bordeaux Science Agro, INRA, 33140, Villenave d'Ornon, France.
authors.forename: Teresa E
authors.initials: TE
authors.lastname: Gimeno
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Catriona A
authors.initials: CA
authors.lastname: Macdonald
authors.affiliation: Oak Ridge National Laboratory, Environmental Sciences Division and Climate Change Science Institute, 1 Bethel Valley Road, Oak Ridge, TN, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Norby
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Sally A
authors.initials: SA
authors.lastname: Power
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Tjoelker
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: David S
authors.initials: DS
authors.lastname: Ellsworth
mesh_terms: D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000378:metabolism*; D057231:Climate Change; D017753:Ecosystem; D005052:Eucalyptus / Q000378:metabolism*; D065928:Forests; D010788:Photosynthesis; D014867:Water
chemical_list: D014867:Water; D002245:Carbon Dioxide
keywords: Eucalyptus tereticornis; carbon dioxide; drought; ecosystem model; phosphorus