invasion of marsh islands by phragmites australis
TRANSCRIPT
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Invasion of Marsh Islands by Phragmites australis
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Morphology• Perennial Rhizomatous Grass• 1-4 m tall (North America)• 50-100 stem m-2
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Reproduction• Seeds• Rhizome fragments• Vegetative expansion
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Invasive Species• Phragmites
– Large biomass production, restricts water movement
– Reduces light levels
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Invasive Species• Phragmites
– Expanding into native Scirpus and Spartina marshin LA
– Impedes nekton movement– Alteration of
nutrient cycling
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Hypotheses• Invasion depends
on: – island perimeter– Island area
• Invasion components– Establishment– expansion
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Predictions• Large Perimeter
– Entry points
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Predictions• Large Area
– Available space– Expansion
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Methods• 18 islands• Rockefeller State Wildlife Refuge• Range of areas, perimeters
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Methods• Perimeter Hypothesis
– Island Perimeter versus Rate of New Stand Formation
Island 1998 2005 2009
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Methods• Area Hypothesis
– Island Area versus Rate of Increase in Proportion Phragmites
Island 1998 2005 2009
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Methods• Perimeter and Area Hypothesis
– Island Perimeter/Area versus Proportion Island Area Phragmites
Island 1998 2005 2009
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Problems• Invasion rate decreased 2005-2009
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Hurricanes
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• No decrease in stand formation
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• Stand Formation 1998-2009• Stand Expansion 1998-2005• Only concerned with, “If Phragmites is
increasing…”
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Limitations• Sample Size
– Expand to more islands, refuges• Time Range
– More years• Semester
– Lack of statistics
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Conclusions• Perimeter effect?
– Yes• Area effect?
– No (maybe)