Abstract

Crassulacean acid metabolism (CAM) was modeled by taking a system dynamics (SD) approach. SD considers that the interplay between elements of a complex system have the capacity to explain counterintuitive non-linearities arising from ostensibly simple inputs. The model allowed measured physiological constants to be quantitatively related to CAM expression. Simulated CAM -expression for Kalanchoë daigremontiana displayed strong correlation with measured gas-exchange and malic-acid accumulation (R2=0.931, 0.852 respectively). The four-Phases of CAM -expression were further resolved into parameters that rate-limit carbon-uptake over the diel-cycle. Next, a geospatial spatial model of CAM productivity based on Nobel environmental productivity index methodology (EPI) for the bioenergy candidates A. tequilana and O. ficus-indica will be presented. Yield simulations were performed under the four representative concentration pathways (RCPs) in the IPC Cs 5th Assessment Report. Simulations for O. ficus-indica suggest that viable yields (> 5 Mg ha-1 yr-1) on low-grade lands have the capacity to meet ‘extreme’ bioenergy demand targets (>600 EJ yr-1) without using high-grade agricultural land or contributing to deforestation, and will continue to do so under the worst-case climate change scenario.