ChrisMorgan_SeniorThesisPresentationWeb
- 1. Do Seed Traits Mediate Plant Community Changes in Wisconsin’s Unburned Prairies? Senior Honors Thesis by Christopher Morgan
- 2. What is a Prairie? • Largely made up of grasses, sedges, and flowering plants known as forbs • Biodiversity Hotspot • Fire-adapted communities
- 3. Background Information • Natural fires caused by lightning strikes • Species require heat to germinate • Increased fire suppression since 1950s • Consensus of fire importance – more prescribed burns need to be taking place to be ecologically effective
- 4. Current State of Prairies • WI Pre-European Settlement: 2,000,000 acres of prairie – Now: 12,000 scattered acres • Prairie remnants largely fire suppressed – potential shift in plants best suited to novel ecosystem • Non-native species up 500% since 1950 – Make up >60% total species diversity in some cases
- 5. This Study • Changes to landscape & fire regime raise questions as to how plant (& animal) communities respond to change • Studying plant traits tells much about change • Goal: quantify change in species composition and their seed traits as underlying mechanisms of that change
- 6. Hypotheses Burned Ideal sites Large or expanding patches Medium seed coats Low mass High shape index Unburned Less than ideal sites Small or shrinking patches Thick seed coats High mass Low shape index
- 10. Methods • Measure: – Seed Mass – Seed Coat Thickness – Seed Shape Index (0 being perfectly spherical) For each species found at our sites • Classify – Burned – Unburned
- 11. Carya ovata (shagbark hickory)
- 13. Community Averages • Seed trait means averaged for each site – Based on species present • Seed Mass Example: Species 1 2 u Species 2 4 u Species 3 10 u Community Average: 5.33 u
- 14. Spatial Analysis
- 15. 1 km chosen as it’s roughly the max distance seeds can disperse
- 18. Neat Groupings by Site Type 1950s 2010s Burned 2010s Unburned Site Type SeedMass Seed Mass and Fire History
- 19. Modest Correlation with Mass 1950s 2010s Burned 2010s Unburned Site Type SeedCoatThickness Seed Coat Thickness and Fire History
- 20. Results Burned Ideal sites Large or expanding patches ~ Medium seed coats ~ ✓ Low mass ~ ✓ High shape index ~ Unburned Less than ideal sites Small or shrinking patches ~ Thick seed coats ~ ✓ High mass ~ ✓ Low shape index ~ ✓ = Correlation Predicted ~ = No significant Correlation X = Correlation Opposite Predicted
- 21. Discussion • 2010s seed mass considerably higher overall – Unburned higher than burned • Shape, seed mass: strong negative correlation • Seed coat thickness, mass: somewhat proportional • No strong relationship between prairie size and seed traits – but when paired with fire there is • Fire the real driver of community composition
- 22. Land Mgmt Implications • Prescribed burns used, but not widely enough • Lack of prairie fires even since 1950s has had significant influence on make-up of prairies – Ex: larger seeds have disproportionate nutrient reserves – better at penetrating leaf litter layer • Better effort to remove stigma from burns and return them as a normalized management tool
- 23. Questions?