Hurricane disturbance and the regeneration of Lysiloma latisiliquum (Fabaceae): a tropical tree in south Florida

Abstract

Large-scale catastrophic disturbances such as hurricanes may be critical events for the regeneration of late secondary canopy tree species. The impact of Hurricane Andrew, a severe Category 4 hurricane, on the tropical tree Lysiloma latisiliquum was examined in three south Florida subtropical forests along a gradient of hurricane disturbance (high, moderate, none). The population closest to the northern eye wall of the hurricane had the highest mortality and most severe structural damage while the population near the southern eye wall of the hurricane experienced less mortality and damage. Posthurricane reproduction was least in the disturbed sites while the undisturbed site had extensive reproduction in both 1993 and 1994. Average seed production was low due to seed predation by a bruchid beetle but some populations experienced spatial and temporal escape from this seed predator. Germination from a dormant seed bank occurred only at the most severely disturbed site in 1992. Seed germination was associated with both tip-up pits and high understory light levels. In experimental trials, fluctuating heat treatments for 5 days increased seed germination. Severe hurricane disturbance is believed to have triggered germination from a dormant seed bank through strong diurnal soil temperature fluctuations resulting from extensive canopy removal. In south Florida, the temporal and spatial dynamics of both hurricane and fire disturbance are predicted jointly to influence the population dynamics of this canopy tree species.