Long-term vegetation dynamics following water level stabilization in a prairie marsh

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Grosshans, Richard E.
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The objective of this study is to examine the long-term vegetation dynamics of a prairie marsh following water level stabilization. We hypothesize that disruption of the natural disturbance regime (flood-drought cycles) in prairie marshes increases the influence of competition among macrophyte species. An increase in competitive interactions results in elimination of subordinate species, while consolidating the abundance of competitive dominants. We used colour infrared aerial photography, GPS and GIS, microtopographic maps, and ground-truthing surveys to examine the role of interspecific competition in structuring wetland communities in the Marsh Ecology Research Program (MERP) experimental marshes at Delta Marsh, Manitoba, Canada. The MERP complex consists of ten sand-diked and two "control" marshes, each between ca. 5-7 ha in area. Water level fluctuations in Delta Marsh were artificially stabilized in 1961, disrupting the natural flood-drought cycle. Since 1989, water levels in the twelve marshes have been left to equilibrate with the surrounding marsh. At present, six emergent plant zones characterize the twelve marshes: salt-tolerant species, annuals, reed grass, whitetop, cattail and bulrush. (Abstract shortened by UMI.)