COMPUTER-SIMULATION OF TREE GROWTH PERIODICITY AND CLIMATIC HYDROPERIODICITY IN TROPICAL FORESTS

In most tropical trees, vegetative and reproductive development are distinctly periodic, but often poorly correlated with seasonal climatic change. Growth periodicity of individual trees is proposed here to reflect primarily an endogenous rhythm of vegetative growth resulting from periodic leaf replacement. This endogenous periodicity determines the species-specific timing of flowering and can be entrained secondarily to seasonal changes in water stress. These assumptions have been incorporated into a simple computer model which illustrates the effects of various degrees of seasonal drought on tree growth periodicity. A range of periodic growth patterns observed in individual trees and tree communities subject to increasing seasonal drought can be simulated by the model suggesting that causal interactions similar to those operating in the model are sufficient to determine growth periodicity in tropical trees and forests.