1. A model-data comparison of gross primary productivity: Results from the North American Carbon Program site synthesis
- Author
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Schaefer, Kevin, Schwalm, Christopher R, Williams, Chris, Arain, M Altaf, Barr, Alan, Chen, Jing M, Davis, Kenneth J, Dimitrov, Dimitre, Hilton, Timothy W, Hollinger, David Y, Humphreys, Elyn, Poulter, Benjamin, Raczka, Brett M, Richardson, Andrew D, Sahoo, Alok, Thornton, Peter, Vargas, Rodrigo, Verbeeck, Hans, Anderson, Ryan, Baker, Ian, Black, T Andrew, Bolstad, Paul, Chen, Jiquan, Curtis, Peter S, Desai, Ankur R, Dietze, Michael, Dragoni, Danilo, Gough, Christopher, Grant, Robert F, Gu, Lianhong, Jain, Atul, Kucharik, Chris, Law, Beverly, Liu, Shuguang, Lokipitiya, Erandathie, Margolis, Hank A, Matamala, Roser, McCaughey, J Harry, Monson, Russ, Munger, J William, Oechel, Walter, Peng, Changhui, Price, David T, Ricciuto, Dan, Riley, William J, Roulet, Nigel, Tian, Hanqin, Tonitto, Christina, Torn, Margaret, Weng, Ensheng, Zhou, Xiaolu, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
- Subjects
NET ECOSYSTEM PRODUCTIVITY ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,SUB-ALPINE FOREST ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,STOMATAL CONDUCTANCE ,SOIL-MOISTURE ,DIOXIDE FLUXES ,GLOBAL VEGETATION MODEL ,CO2 EXCHANGE ,Earth and Environmental Sciences ,Settore BIO/07 - ECOLOGIA ,BOREAL FORESTS ,INTERANNUAL VARIABILITY ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment ,ComputingMilieux_MISCELLANEOUS ,HIGH-ELEVATION - Abstract
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 degrees 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 degrees 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 as epsilon(max) (LUE), V-cmax (unstressed Rubisco catalytic capacity) or Jmax (the maximum electron transport rate).
- Published
- 2012