B11C-0431
Assumption Centred Modelling of Ecosystem Responses to CO2 at Six US Atmospheric CO2 Enrichment Experiments.

Monday, 14 December 2015
Poster Hall (Moscone South)
Anthony P Walker1, Martin G De Kauwe2, Belinda E Medlyn3, Soenke Zaehle4, Kristina A Luus4, Edmund Ryan5, Jianyang Xia6, Richard J Norby1 and The FACE-MDS Team, (1)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (2)Macquarie University, Sydney, Australia, (3)Western Sydney University, Hawkesbury Institute for the Environment, Sydney, Australia, (4)Max Planck Institute for Biogeochemistry, Jena, Germany, (5)Arizona State University, Tempe, AZ, United States, (6)University of Oklahoma Norman Campus, Norman, OK, United States
Abstract:
Plant photosynthetic rates increase and stomatal apertures decrease in response to elevated atmospheric CO[2] (eCO2), increasing both plant carbon (C) availability and water use efficiency. These physiological responses to eCO2 are well characterised and understood, however the ecological effects of these responses as they cascade through a suite of plant and ecosystem processes are complex and subject to multiple interactions and feedbacks. Therefore the response of the terrestrial carbon sink to increasing atmospheric CO[2] remains the largest uncertainty in global C cycle modelling to date, and is a huge contributor to uncertainty in climate change projections.

Phase 2 of the FACE Model-Data Synthesis (FACE-MDS) project synthesises ecosystem observations from five long-term Free-Air CO[2] Enrichment (FACE) experiments and one open top chamber (OTC) experiment to evaluate the assumptions of a suite of terrestrial ecosystem models. The experiments are: The evergreen needleleaf Duke Forest FACE (NC), the deciduous broadleaf Oak Ridge FACE (TN), the prairie heating and FACE (WY), and the Nevada desert FACE, and the evergreen scrub oak OTC (FL).

An assumption centered approach is being used to analyse: the interaction between eCO2 and water limitation on plant productivity; the interaction between eCO2 and temperature on plant productivity; whether increased rates of soil decomposition observed in many eCO2 experiments can account for model deficiencies in N uptake shown during Phase 1 of the FACE-MDS; and tracing carbon through the ecosystem to identify the exact cause of changes in ecosystem C storage.

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