A model-data comparison of gross primary productivity: Results from the North American Carbon Program site synthesis
Article first published online: 19 JUL 2012
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Biogeosciences (2005–2012)
Volume 117, Issue G3, September 2012
How to Cite
2012), A model-data comparison of gross primary productivity: Results from the North American Carbon Program site synthesis, J. Geophys. Res., 117, G03010, doi:10.1029/2012JG001960., et al. (
- Issue published online: 19 JUL 2012
- Article first published online: 19 JUL 2012
- Manuscript Accepted: 26 MAY 2012
- Manuscript Revised: 16 MAY 2012
- Manuscript Received: 20 JAN 2012
- NOAA. Grant Numbers: NA07OAR4310115, N9-TE09-26
- gross primary productivity;
- model performance;
 Accurately simulating gross primary productivity (GPP) in terrestrial ecosystem models is critical because errors in simulated GPP propagate through the model to introduce additional errors in simulated biomass and other fluxes. We evaluated simulated, daily average GPP from 26 models against estimated GPP at 39 eddy covariance flux tower sites across the United States and Canada. None of the models in this study match estimated GPP within observed uncertainty. On average, models overestimate GPP in winter, spring, and fall, and underestimate GPP in summer. Models overpredicted GPP under dry conditions and for temperatures below 0°C. Improvements in simulated soil moisture and ecosystem response to drought or humidity stress will improve simulated GPP under dry conditions. Adding a low-temperature response to shut down GPP for temperatures below 0°C will reduce the positive bias in winter, spring, and fall and improve simulated phenology. The negative bias in summer and poor overall performance resulted from mismatches between simulated and observed light use efficiency (LUE). Improving simulated GPP requires better leaf-to-canopy scaling and better values of model parameters that control the maximum potential GPP, such asεmax (LUE), Vcmax (unstressed Rubisco catalytic capacity) or Jmax (the maximum electron transport rate).