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Monday, May 26, 2008 - 2:30 PM
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Colonization and succession of stream communities in glacier bay, Alaska; Contribution to successional theory?
Alexander M. Milner, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom and Anne Robertson, School of Human and Life Sciences, Roehampton University, Holybourne Avenue, London, United Kingdom.
How stream ecosystems fit with general successional theory has not been widely addressed due to the lack of long-term studies on stream channels at a sufficiently large enough spatial scale. Watersheds that have emerged from under the ice in the offers us an opportunity to redress this imbalance by examining their development with reference to concepts of succession and community assembly. Dispersal constraints have typically influenced succession as non-insect taxa require considerably longer to establish than non-insects. A 30-year record of site-specific temporal succession in one system suggests that both biotic and abiotic factors have influenced successional pathways, with the abiotic variables of water temperature, dispersal limitations and geomorphological habitat dominating. Although there is little support for the tolerance model in terrestrial and freshwater ecosystems, we suggest it is a major mechanism of macroinvertebrate community assembly in this stream succession. Most taxa, with the exception of the cold-tolerant first colonizers, have persisted within the community following colonization, although relative abundance has changed markedly with time. Extinctions have principally been within the chironomid and meiofauna taxa. However, biotic processes do influence colonization and succession. Redd digging by spawning salmon creates disturbed patches that facilitate the persistence of some early colonizers, and riparian vegetation facilitates colonization by caddisflies and chironomids. We suggest that both deterministic and stochastic elements influence succession and community assembly in streams.
Web Page: succession, colonization, theory