Ecosystem- and community-level effects of biological invasion

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Invasive species are at the forefront of current environmental issues. Biological invaders can disrupt ecosystems by altering fundamental ecosystem processes like competition, plant growth and decay. To manage invasions, we must first understand the consequences of invasion and weigh these against the environmental costs of control activities. Understanding how invasive species influence ecosystems and communities also provides us with insight into how communities assemble, and what determines the capacity of ecosystems to resist or recover from disturbance. These fundamental ecological issues are the focus of my research program. As a model system, I propose to examine the ecosystem effects of invasion by non-native Phragmites australis (Common Reed) in freshwater marshes. Our knowledge of the effects of this aggressive invader in freshwater is woefully out-dated and inadequate. To better understand how Common Reed invasion affects: i) wetland structure; ii) wetland ecosystem processes (e.g., plant growth and decomposition); and, iii) use of wetlands by migratory and imperiled birds, I am proposing an innovative field-based research program with two major components. 1. A comparison of basic ecosystem processes between invaded and uninvaded wetland plots. Plant growth, decay, and carbon storage will be compared between plots invaded by Common Reed and plots in cattail and marsh meadow communities. This component of the research program will include a litter transplant experiment and direct soil characterizations to tease apart whether differences in growth and decay between invaded and uninvaded plots are due to differences in litter composition or due to variability in environmental conditions. 2. A comparison of bird abundance and community composition between time periods that represent pre-invasion, new invasion, and established invasion. Limited previous work has shown that in the early stages of invasion effects on the bird community composition can be minor, and that bird abundance can actually be enhanced by Common Reed. However, it is unlikely that any positive effect of Common Reed will persist once the invasion has become established. For this first phase of my Discovery program, research will be conducted at Long Point, Ontario. The Long Point wetlands constitute 70% of all wetland habitat on the north shore of Lake Erie, and are a migratory bird staging area of continental importance. The dense, impenetrable monocultures characteristic of established Common Reed stands could imperil species at risk (e.g., Least Bittern) in this and other wetlands, and further study is urgently needed to inform management decisions and set restoration priorities. Results of this research will also contribute to addressing larger questions about invasion ecology and the resiliency of wetlands. Additionally, my proposed program will foster partnerships and knowledge transfer between the University of Waterloo, Bird Studies Canada, the Long Point National Wildlife Area, and the Long Point Research and Education Centre. This will lead to the training of highly skilled personnel: the next generation of environmental scientists and conservation biologists who will tackle ecological crises of the future.