Phenology and Ecophysiology of the Tropical Tree, Tabebuia Neochrysantha (Bignoniaceae)

Abstract

Phenology and seasonal variations in water stress, as reflected in variations in stem circumference, were monitored throughout 1978 in numerous Tabebuia neochrysantha growing at several dry and wet sites in a lowland deciduous forest in Guanacaste, Costa Rica. The rate of leaf fall during the early dry season was strongly correlated with the decline in soil moisture and increasing water stress of the trees. Without exception, recovery from water strees was required for flowering and shoot emergence. At dry sites rehydration occurred only after isolated rain showers or irrigation; at wet sites it took place during continued drought, probably as a consequence of the decrease in transpiration during leaf fall. Flowering has been observed to occur at any time between the beginning (December) and end (May) of the dry season. Differences in the timing and intensity of flowering as well as in the timing of leaf fall and shoot emergence can be accounted for by site-dependent differences in the rates of desiccation and rehydration of trees in conjunction with year-to-year variation in the timing and intensity of rainfall. No evidence for the control of seasonal development by other environmental factors, such as variations in temperature of photoperiod, was obtained.