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Does Allelopathy Explain the Scarcity of Spruce and Fir Trees in the Beech Gaps of Great Smoky Mountains National Park? Monica Poteat Dr. David Vandermast Elon University
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Beech Gaps Great Smoky Mtns. High elevations Deciduous – American beech (Fagus grandifolia) Evergreen – Red spruce (Picea rubens) – Fraser fir (Abies fraseri)
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Other Theories Height difference (Whitaker 1956) Inadequate seed rain (Pavlovic 1981) Lack of shade tolerance (Harlow et al. 1991) Beech soil pH/chemistry (Russell 1953; Fuller 1977)
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Allelopathy The production of biomolecules by one plant species which can inhibit the germination and/or growth of other plant species (Rizvi et al. 1992)
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Hypothesis Beech allelopathy inhibits the germination and mass accumulation of red spruce and Fraser fir seeds
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Experimental Set-Up Species Used: Lettuce (Lactuca sativa) Red spruce Fraser fir Soil Treatments: Top Soil Beech forest soil Watering Treatments: Deionized Water Leachate – 1:5 ratio of beech forest leaves and deionized water
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Treatment Set-Up Top Soil/ dH 2 0 Beech soil/ dH 2 0Top soil/Leachate Beech soil/ Leachate
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RESULTS: LETTUCE Top Soil/ dH 2 0 Beech soil/ Leachate
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A AB B Average Germination of Lettuce
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Top soil- dH 2 O Beech soil- dH 2 O Top soil- Leachate Beech soil- Leachate A B A B Treatment Average ABM of Lettuce
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RESULTS: RED SPRUCE Top soil- dH 2 O Beech soil- Leachate
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A AB B Average Germination of Red Spruce
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Top soil- dH 2 O Beech soil- dH 2 O Top soil- Leachate Beech soil- Leachate Treatment A B A AB Average ABM of Red Spruce
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RESULTS: FRASER FIR Top soil- dH 2 O Beech soil- Leachate
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A B AB Average Germination of Fraser Fir
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Top soil- dH 2 O Beech soil- dH 2 O Top soil- Leachate Beech soil- Leachate Treatment A B AB C Average ABM of Fraser Fir
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Important Findings Leachate germinations all lower than deionized water (even if not statistically significant) Leachate and/or beech soil treatments significantly reduce germination and/or mass – Different species respond differently to allelogens Sickly seedlings
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What our findings mean in relation to... Other allelopathic studies – American beech leaf leachate has been shown to lower leaf area and biomass of the seedlings of sugar maple (Hane et al. 2003) Competitive Exclusion Beech Bark Disease
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Beech are a foundation species within gaps – Define community – Create stable conditions Why is this important? http://fisc.er.usgs.gov/c1258_Dodd/circ1258_8a.jpg
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Conclusion Allelopathy is an important mechanism through which beech forests competitively exclude the red spruce and Fraser fir.
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Acknowledgments Dr. Vandermast Elon University SURE program Elon College Fellows Program Great Smoky Mountains National Park (permits) – Keith Langdon, Supervisor of Science Projects – Dr. Michael Jenkins, Ecologist Judy Poteat
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