Collaborative Research: Lightning as an agent of tropical tree mortality

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Lightning is an exceptionally powerful natural phenomenon; its destructive effects have been a source of fear and fascination for humans throughout history. Scientists have a relatively good understanding of the physics of lightning, but its ecological importance at the landscape scale--especially its role as an agent of tree death--remain unclear. Measuring the effects of lightning in tropical forests is important because lightning frequency is expected to increase by as much as 50% over the next few decades as the climate warms. This research will provide the foundation for understanding how such changes will affect forest dynamics and ecosystem processes such as carbon cycling. Specifically, it will determine how the size, location, and species identity of a tree affects the probability that it will be killed by lightning; and it will measure the amount of dead wood present in a forest due to lightning strikes. Tropical rainforests are the world's best classroom for studying biodiversity and ecosystem processes, and this project provides outstanding opportunities for students at the University of Louisville and the University of Alabama in Huntsville to gain valuable first-hand research experience in an international setting. The field site in Panama is a popular tourist destination, thus the project provides a unique opportunity for participants to interact regularly with the public. Prior studies by the researchers on rainforest canopies attracted international media attention, and this project is expected to generate similar public interest. Finally, this project includes a collaboration with the Director of Education at the Kentucky Science Center, who will produce museum displays highlighting this research, and will organize public discussions with project participants in an informal Science Café setting. The principal objective of this study is to quantify the ecological effects of lightning on trees and lianas (woody vines) in a lowland tropical forest. The research employs the latest high-tech lightning sensors in combination with digital video cameras to record and precisely locate cloud-to-ground lightning flashes over approximately 20 square km of forest canopy in real time. The central hypothesis is that lightning is a major agent of tropical tree and liana mortality, and thereby plays an important role in carbon cycling and plant-feeding insect distributions. The work will integrate information from field ecology, remote sensing, atmospheric science, and physics to answer three basic questions: 1) What factors affect the probability of lightning strikes to tropical trees?; 2) What is the amount of carbon in the form of dead wood produced by lightning on a forest-wide scale?; and 3) Does the distribution of lightning damage affect canopy insect distributions? This work will improve knowledge of tropical forest dynamics by measuring the effects on lightning on different forest components across the landscape. Specifically, it will uncover key interactions among lightning, lianas, trees, and insects. As a whole, the project will provide the first accurate measure of lightning distribution, frequency, and biological effects in a tropical forest.