Publication Date:
2016-03-07
Description:
The response of terrestrial ecosystems to rising atmospheric CO 2 concentration (C a ), particularly under nutrient limited conditions, is a major uncertainty in Earth System models. The Eucalyptus Free-Air CO 2 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 post-experiment model intercomparison. Simulated responses of annual net primary productivity (NPP) to elevated C a 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. This article is protected by copyright. All rights reserved.
Print ISSN:
1354-1013
Electronic ISSN:
1365-2486
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Geography
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