SGER: Unpredictable Events of Catastrophic Proportions in Temparate Forest Ecosystems: Developing a Baseline to Assess Cascading Effects and Coupled Interactions

Indiana University, Bloomington IN

Investigators

Abstract

Recently developed ecological theories had identified major disturbance events as crucial factors in large-scale environmental change and evolution. Punctuated equilibrium and chaos theories posit shifts in systems between alternative stable states. Inquiries into the complex dynamics of these relatively abrupt shifts generally have taken place after major disturbances have occurred, with relatively little data available to characterize conditions prior to the events because of their suddenness and unpredictability. Periodic emergence of cicadas in massive numbers are predictable, but they occur infrequently enough to constitute an excellent model of unpredictable disturbance events of catastrophic proportions. This Small Grant for Exploratory Research will establish a set of baseline measurements in central Indiana starting in the summer of 2002 in anticipation of a major cicada outbreak in mid-2004. Cicada outbreaks occur every 17 years in central Indiana, where the size of the outbreak is among the largest found anywhere in the U.S. The time period between outbreaks is so long that most elements of the forest system that the cicadas inhabit effectively have no working memory of the form and character of the outbreak. Before the outbreak, cicadas underground are massive consumption of tree root systems, while after the outbreak, they can rapidly defoliate tree canopies. They become prey to a number of species, frequently inducing "predator saturation" as wildlife gorge on the seemingly endless supply of insects, an eating pattern that can dramatically alter the survival and reproduction rates of those predators during the year of the outbreak and in following years. The laying of eggs can lead to damage or death of affected trees, and loss of tree canopy can alter the microclimatology of the understory and affect transpiration rates, which in turn affects groundwater and surface stream hydrology. In order to develop baseline information against which to evaluate the impacts of the 2004 cicada outbreak in central Indiana, this research team, which includes members drawn from geography, biology, geology, and public and environmental affairs departments, will begin taking a series of measurements in mid-2002. Among variables to be measured are nutrient dynamics, hydrology, canopy cover, tree physiology, seedling establishment, and socioeconomic factors. This award will help establish baseline measurements from which follow-up studies can be conducted in the coming years. In addition to laying the groundwork for a broad range of inquiries into interactions between natural and human systems, the project will have positive broader impacts, including the involvement and training of undergraduate and graduate students and the establishment of databases that can be used for a broad range of inquiries.