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Significance: The wetland habitat models are very significant, as many of the other wetland PIs are dependant on the habitat model outputs. The meadow marsh specifically represents vegetation that typically develops between the maximum long-term high water level and the long-term mean. Plant species within this community are intolerant to prolonged flooding, but occasional flooding is required to prevent woody plant species from expanding downslope into the meadow marsh community. More importantly, periodic low water-level cycles are required to arrest the expansion of aggressive emergent plants upslope into the meadow community. During the low water period, emergent plant species will die back at higher elevations where the hydrology is no longer suitable. Coincidently, the hydrology does become suitable for meadow marsh plant species, which will expand, and result in the meadow marsh habitat expanding downslope. This low water cycle is of critical importance for maintaining the area of meadow marsh within Lake Ontario coastal wetlands. As water levels fluctuate between the high and low water-level cycles, the meadow marsh will typically also contain some emergent, shrub, or upland plant species. The relative amount of these species is dictated by the years since the last high or low water-level cycle. For this reason, the meadow marsh community supports a very great diversity of plant species but occurs in a relatively narrow hydrologic range in comparison to the other wetland vegetation communities.
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