A global scale mechanistic model of the photosynthetic capacity

Thursday, 17 December 2015: 11:05
2008 (Moscone West)
Chonggang Xu1, Ashehad Ashween Ali2, Rosie Fisher3, Stan D Wullschleger4, Alistair Rogers5, Nathan G McDowell1 and Cathy Jean Wilson1, (1)Los Alamos National Laboratory, Los Alamos, NM, United States, (2)Organization Not Listed, Washington, DC, United States, (3)National Center for Atmospheric Research, Boulder, CO, United States, (4)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (5)Brookhaven National Laboratory, Upton, NY, United States
Although plant photosynthetic capacity as determined by the maximum carboxylation rate (i.e., Vc,max25) and the maximum electron transport rate (i.e., Jmax25) at a reference temperature (generally 25oC) is known to vary substantially in space and time in response to environmental conditions, it is typically parameterized in Earth system models (ESMs) with tabulated values associated to plant functional types. In this study, we developed a mechanistic model of leaf utilization of nitrogen for assimilation (LUNA V1.0) to predict the photosynthetic capacity at the global scale under different environmental conditions, based on the optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The LUNA model was able to reasonably well capture the observed patterns of photosynthetic capacity in view that it explained approximately 55% of the variation in observed Vc,max25 and 65% of the variation in observed Jmax25 across the globe. Our model simulations under current and future climate conditions indicated that Vc,max25 could be most affected in high-latitude regions under a warming climate and that ESMs using a fixed Vc,max25 or Jmax25 by plant functional types were likely to substantially overestimate future global photosynthesis.