Climatic periodicity, phenology, and cambium activity in tropical dry forest trees

The seasonal time course of vegetative phenology and cambium growth is compared for tree species from Central America and Asia growing in tropical climates with a long, severe dry season. Although the inhibition of plant growth by water stress is well established, responses to seasonal drought vary widely among such trees, and their annual development is not well synchronized by climatic seasonality. In deciduous trees growing at microsites with low soil moisture storage, phenology and cambium growth are well correlated with each other and with seasonal rainfall, and most trees have distinct annual rings. Phenology and cambium growth are progressively uncoupled from climatic seasonality in brevideciduous and evergreen trees growing at microsites with large soil water reserves which buffer trees against seasonal drought and thus may prevent the formation of distinct annual rings. There is some experimental evidence concerning the control of growth initiation in apical meristems and the cambium, but little is known about the mechanisms which arrest growth and determine qualitative changes in organ development and cambium cell differentiation.