Model predictions of the response of transpiration to elevated atmospheric CO₂ concentration (Ca) are highly variable among models. To better understand and constrain this variability among models, we conducted an intercomparison of 11 ecosystem models applied to two forest free-air CO₂ enrichment (FACE) experiments. We analysed model structures in order to identify the key underlying assumptions causing differences in model predictions of transpiration. We then benchmarked the models against data to identify model assumptions that are incorrect or are large sources of uncertainty. Key model assumptions included: whether assimilation (A) and stomatal conductance (gs) are coupled; how strongly the ratio of A/gs increases with Ca; the magnitude of the boundary layer feedback on transpiration; the relative importance of canopy interception; and thresholds and mechanisms of soil moisture stress impact on fluxes. The study yields a straightforward framework for analysing and evaluating model predictions of transpiration responses to rising Ca.
|American Geophysical Union Fall Meeting (45th : 2012)
|San Francisco, CA
|3/12/12 → 7/12/12
- Water use
- Carbon dioxide