Do Differential Responses to Desiccation, Herbivory and Light Determine the Habitat Specializations of Rainforest Trees Along a Rainfall Gradient?

University Of Utah, Salt Lake City UT

Investigators

Abstract

Ecosystems provide many services to humankind. Throughout history, forests have fulfilled many human needs. Forests provide water stores for urban areas. Wood, from temperate and tropical forests, also plays a vital role in the US and world economies. Moreover, forests also harbor astonishing biodiversity. These observations apply especially to tropical forests that, despite their evident importance, are converted at an unsustainable rate. While it is widely appreciated that tropical forests display high diversity, it also is true that sites separated by only kilometers differ considerably in tree (and animal) species. In order to protect and manage such forests, we must understand the factors that determine the distributions and abundances of trees. Although the very complex patterns of distribution of tropical trees have long been recognized, the factors that determine distribution are not understood. Many argue that rainfall and drought are important factors, but scientific demonstrations are lacking. In lowland tropical forests, the principal determinants of tree distributions probably are drought (rainfall), light availability in the dim understory and plant enemies (herbivores). In this project, investigators will evaluate experimentally the relative importance of these three factors in determining tree distributions across the Isthmus of Panama. Panama provides an excellent laboratory since the tree species on the wet, Caribbean side are largely absent on the dry, Pacific side (and vice versa) and the processes that cause this pattern are unknown. Quantifying the impact of rainfall, light and herbivores on tree distributions has broad applications for the protection and management of tropical forests worldwide.