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Title: Using models to guide field experiments: a priori predictions for the CO 2 response of a nutrient- and water-limited native Eucalypt woodland

One major uncertainty in Earth System models is the response of terrestrial ecosystems to rising atmospheric CO 2 concentration (Ca), particularly under nutrient-lim- ited conditions. The Eucalyptus Free-Air CO 2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodlands, presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. Moreover, we applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experi- ments, 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 intercompari- son. 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 nutri- ent uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Finally, knowledge of the causesmore » 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.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [5] ;  [3] ;  [6] ;  [7] ;  [6] ;  [8] ;  [4] ;  [5] ;  [5] ;  [9] ;  [5] ;  [4] ;  [5] ;  [5] ;  [5]
  1. Univ. of Western Sydney, NSW (Australia). Hawkesbury Inst. for the Environment; Macquarie Univ., North Ryde (Australia). Dept. of Biological Sciences
  2. Macquarie Univ., North Ryde (Australia). Dept. of Biological Sciences
  3. Max Planck Society, Jena (Germany). Max Planck Inst. for Biogeochemistry
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division and Climate Change Science Inst.
  5. Univ. of Western Sydney, NSW (Australia). Hawkesbury Inst. for the Environment
  6. Lund Univ. (Sweden). Dept. of Physical Geography and Ecosystem Science
  7. Commonwealth Scientific and Industrial Research Organization (CSIRO), Aspendale, VIC (Australia). Oceans and Atmosphere Flagship
  8. CSIRO Oceans and Atmosphere Flagship, Private Bag 1 Aspendale Vic. 3195 Australia
  9. Univ. of Western Sydney, NSW (Australia). Hawkesbury Inst. for the Environment; National School of Agricultural Engineering, Bordeaux (France). ISPA
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Global Change Biology
Additional Journal Information:
Journal Volume: 22; Journal Issue: 8; Journal ID: ISSN 1354-1013
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; carbon dioxide; drought; ecosystem model; eucalyptus tereticornis; phosphorus
OSTI Identifier: