Research

Lightning-tree interactions

Although lightning damages millions of trees each year, our understanding of lightning-caused mortality relies on anecdotal information.  Lightning is commonly associated with wildfires and these fires are an important consequence of lightning.  However, approximately 99% of lightning strikes do not cause fires and this percentage increases in tropical forests where lightning frequency is highest.  Our research explores the ecological effects of these strikes that do not cause fires.

How does lightning kill trees and why does it typically kill some trees but not others?  As part of a larger project coordinated by Steve Yanoviak and Phillip Bitzer, I am investigating phenomena related to this question.  This ongoing work has demonstrated that lightning typically causes group tree mortality in a neotropical forest, and our preliminary results suggest it is a major cause of large tree death.  I am interested in how the electrical properties of trees influence tree response to lightning and how lightning strikes induce post-strike invasion by deleterious invertebrates and microbes.  Using field-collected electrical data, we modeled lightning-tree interactions and are now collecting empirical evidence to test the predictions of this model in central Panama.  We are also using these field data to quantify the effects of lightning on dead wood production and carbon cycling.  This work is funded by National Science Foundation grants to myself, Dr. Steve Yanoviak, and Dr. Philip Bitzer, and a grant from the National Geographic Society to myself.

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Professor Alyssa Stark (Villanova) assists with the setup of a camera (white box) and accompanying solar panel on an observation tower.
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This image, captured using the camera system pictured above, enabled me to locate the trees killed by this lightning strike.

Carbon Cycling and Decomposition

I am investigating the distribution and decomposition of dead wood in tropical forests.  The greater biodiversity of tropical regions is well known, but faster rates of nutrient cycling make tropical forests special as well.  Nutrient cycling is of particular interest during the current pattern of climate change, as tropical forests are disproportionately important to the global carbon cycle.  The woody tissues of trees are the biggest aboveground component of the carbon cycle, yet how carbon cycles through woody debris remains poorly understood.

I am using a variety of approaches to study the roles of dead wood in tropical forests.  In a collaboration with Emma Sayer, Ed Tanner, and Ben Turner, we used a long-term litter removal and addition experiment to determine how soil nutrient availability affects decomposition over a 15 year period.  Separately, I am working with Helene Muller-Landau to quantify the stocks, fluxes, and spatiotemporal variability of dead wood on Barro Colorado Island in Panama.  Related to this project, I am investigating how decomposition rates change vertically and how these changes are associated with environmental factors (microclimate and nutrient availability) and microbial communities (bacteria, archaea, and fungi).  Finally, I am also investigating how priority effects of canopy-level microbial communities influence ground-level decomposer community assembly and function.  This work is funded by grants from the Smithsonian Tropical Research Institute and the National Science Foundation.

 

 

Swimming Behavior and Orientation

I am interested in how animals perceive and interact with their environment.  Specifically, I am exploring how ants orient and swim to escape from the surface of water.  In collaboration with Steve Yanoviak and Noah Gripshover, we test swimming behaviors of Carpenter ants (i.e., Camponotus pennsylvanicus) in an easily manipulated experimental arena.  This gives us the ability to manipulate visual cues and test how these ants use their eyes to orient.  Currently, we are embarking on a new stage of this research comparing swimming performance and the roles of specific legs between common temperate forest ant species.  Data collection and the investigation into performance was largely driven by the efforts of a student I mentored at the University of Louisville, Noah Gripshover (now a Masters student at the University of Cincinnati). This work is funded by two grants from the Carl C. Cornett Entomological Endowment Fund.