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

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Invasion of Marsh Islands by Phragmites australis

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

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