ABSTRACT
The atmospheric concentrations of the major long-lived greenhouse gases continue to increase because of human activity. Regression-based models use empirically derived relationships between climate and net primary production (NPP) to make predictions. The Terrestrial Ecosystem Model (TEM) is a processed-based ecosystem simulation model that uses spatially referenced information on climate, elevation, soils, vegetation and water availability to make monthly estimates of important carbon and nitrogen fluxes and pool sizes. The TEM generally estimates that nitrogen limitation of NPP is much weaker in tropical forests than in temperate and boreal forests. The application of TEM in this study demonstrates our ability to explore, in a mechanistic manner, the potential consequences of changes in CO2 and climate for NPP across the entire terrestrial surface of the globe. Under contemporary climate conditions in dry regions, TEM generally predicts that water availability limits productivity more than nitrogen availability.
