Abstract
Conditions for the coexistence of trees and grass are explored using a mathematical model describing plant competition for radiation, water and nutrients. The model describes growth of both species in terms of key physiological processes (radiation interception, photosynthesis, respiration, grazing, litterfall, assimilate partitioning, nutrient uptake and water use) and is used to analyse how species compete by depriving each other of resources essential for growth. Changes of growth parameters are shown to lead to shifts in species composition (e.g. through replacement of one species by another).