Multimodel a priori predictions for ecosystem CO2 responses in interaction with nutrient and water limitation.
Quantitative model projections were made for the recently established Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment in Australia. Model simulations were designed to evaluate the experiment data as they are collected and to identify key measurements that should be made to discriminate among competing model assumptions.
Knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the guided experimental data collection will optimally inform future model improvements.
A major uncertainty in Earth system models is the response of terrestrial ecosystems to rising atmospheric carbon dioxide (CO2) concentration, particularly in nutrient-limited environments. The EucFACE experiment, established in a nutrient- and water-limited woodland, presents a unique opportunity to address uncertainty in Earth system models, but can best do so if key model uncertainties have been identified in advance. Researchers applied seven representative vegetation models to simulate a priori possible outcomes from EucFACE. Simulated responses to elevated CO2 of annual net primary productivity (NPP) ranged from 0.5% to 25% across models. The simulated NPP reduction during a low-rainfall year varied even more widely than the CO2 response—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.
Contacts (BER PM)
Daniel Stover and Jared DeForest
Daniel.Stover@science.doe.gov, 301-903-0289; and Jared.DeForest@science.doe.gov, 301-903-1678
Environmental Sciences Division, Climate Change Science Institute
Oak Ridge National Laboratory
The National Climate Change Adaptation Research Facility (NCCARF) and Primary Industries Adaptation Research Network (PIARN) supported this project and travel for the participants to Sydney, Australia. Support was provided via EucFACE as an initiative supported by the Australian Government through the Education Investment Fund and the Department of Industry and Science, in partnership with the University of Western Sydney. Research support came from the Australian Research Council; U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research; and European Community's Seventh Framework Programme (FP7 2007-2013) under grant agreement 238366 (Greencycles II).
Medlyn, B. E., et al. 2016. “Using Models to Guide Field Experiments: A Priori Predictions for the CO2 Response of a Nutrient- and Water-Limited Native Eucalypt Woodland,” Global Change Biology 22, 2834-51. DOI: 10.1111/gcb.13268. (Reference link)
SC-23.1 Climate and Environmental Sciences Division, BER
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