A21G-3117 – Above–Belowground Carbon Allocation in Earth System Models


Xia Song (xsong at utep dot edu)
University of Texas at El Paso
Forrest Hoffman
University of California Irvine; Oak Ridge National Laboratory
Xiaofeng Xu
University of Texas at El Paso
Colleen Iversen
Oak Ridge National Laboratory
Jitendra Kumar
Oak Ridge National Laboratory

Tuesday, December 16, 2014 08:00 AM – 12:20 PM
Moscone South Poster Hall

Above--belowground carbon allocation is a critical mechanism for vegetation growth and its adaptation to the changing environment. The model representation of carbon allocation mechanisms significantly influence the simulated carbon stock and land--atmosphere exchange in Earth System Models (ESMs). Few previous studies, however, have investigated and evaluated the above--belowground carbon allocation in ESMs. In this study, we analyzed carbon density in belowground, total vegetation (above + belowground), and belowground:vegetation ratios of eleven ESMs from the Coupled Model Inter-comparison Project Phase 5 (CMIP5), which were used for the latest IPCC Assessment Report (AR5).

Overall, results of ESMs are not consistent with observational data; both the belowground and total vegetation carbon density are underestimated in tropical/subtropical and temperate regions, while overestimated in arctic/subarctic regions. Moreover, the ratios of belowground:total vegetation carbon are underestimated in all three climate zones. The model--data discrepancies in carbon density vary substantially among biomes, while the ratios of belowground:total vegetation carbon are consistently underestimated across all major biomes expect tropical moist forests. This study indicates that the carbon allocation algorithms in current ESMs need to be improved to better simulate vegetation growth and its responses to global change.

Forrest M. Hoffman (forrest at climatemodeling dot org)