Species-specific growth resilience to drought in a mixed semi-deciduous tropical moist forest in South Asia

Abstract

The frequency and intensity of drought events have increased during the recent decades, particularly in the tropics. Yet, the growth and physiological responses of many tropical tree species to drought are still inadequately understood. We studied the drought resilience of two functionally different canopy tree species (Chukrasia tabularis and Toona ciliata) from a moist tropical forest in Bangladesh during two extreme drought events (1984 and 1999). We quantified four resilience components (resistance, recovery, resilience and relative resilience) of both species to infer drought tolerance of selected trees. Tree radial growth dropped by 44–56% in the drought years, varying with species and drought events. Two species showed no differences in their drought resistance during any of the drought events. However, C. tabularis showed higher recovery and resilience than T. ciliata after the 1999 drought event. T. ciliata showed higher resilience after the 1984 drought event. Linear mixed effect model (LMEM) revealed that growth rates in the two years before and after the drought events had a dominant role in drought responses over tree age, height, diameter, basal area increment and crown exposure, although crown exposure had significant influence on the resistance and the resilience of light demanding T. ciliata. We conclude that diffuse porous and intermediate shade tolerant C. tabularis is more drought tolerant than the ring-porous and light demanding T. ciliata. Since both study species are widely used as plantation species throughout the tropics, our results have important implications for forest managers to take decision on species suitability for plantation programs and to adopt forest management to future climate change conditions.