Climate strongly affects tropical ecosystems and climate change is projected to have increasing consequences in the future. Many tropical forests regularly experience disturbance by hurricanes that create gaps in the forest canopy. These gaps increase light availability in areas where light is the most limiting resource, leading to shifts in population dynamics and species composition. Hurricanes are predicted to increase in intensity (strength) due to climate change, although their frequency is projected to remain the same. Many studies have looked at the potential influence of increasing hurricane frequency on tropical ecosystems, but few of these have looked at the potential impact of changing intensity. To predict the effect of increasing hurricane intensity on tropical ecosystems, I use the newly determined derivative of the stochastic growth rate with respect to the environmental transition matrix (δa/δP).
I apply δa/δP to Ardisia escallonioides, an understory tropical herb found in southern Florida. I find transition matrices for different hurricane intensities and use δa/δP to determine the influence of changing hurricane intensities on the stochastic growth rate a of A. escallonioides.
Results/Conclusions
Preliminary results suggest increasing hurricane intensity increases the stochastic growth rate a of A. escallonioides. Greater hurricane intensity produces a similar effect to greater hurricane frequency (effect of greater hurricane frequency studied in Tuljapurkar and Haridas 2006), with both leading to more time spent in an open canopy state. More canopy openness provides more light, the limiting resource for A. escallonioides, resulting in a higher stochastic growth rate a. However, when hurricane frequency stays the same, but intensity increases, there is a longer progression of canopy closure succession of environmental states between hurricane disturbance events.
With increasing impacts of climate change on ecosystems worldwide, it is important to understand how changes in environmental conditions affect population dynamics. Hurricanes are a prime example, intensely disturbing tropical ecosystems and shifting population dynamics by providing greater light-availability in historically low-light areas. This study provides insight into factors underlying changes in the stochastic growth rate a under changing environmental conditions and provides an empirical test of the newly derived analytical approximation for δa/δP. Validating the accuracy and utility of this new approximation demonstrates its broad applications, creating a resource for studying the effects of climate change and aiding in conservation decisions. This result can be applied across a broad range of disciplines, allowing quick qualitative interpretations of the influence of environmental changes on population dynamics.