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Title:Influence of fire and habitat on the removal of invasive plant seeds by granivores in longleaf pine savannas
Author(s):Krall, Jacqueline
Advisor(s):Fraterrigo, Jennifer M.
Department / Program:Natural Resources and Environmental Sciences
Discipline:Natural Resources and Environmental Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):invasive plants
invasive tree species
invasion ecology
longleaf pine ecosystem
seed predation
wetland ecosystem
upland ecosystem
master's thesis
fire dependent ecosystem
time since fire
Fort Bragg North Carolina
US Army Corps of Engineers
Jonathan Baldwin Turner Fellowship
Abstract:Invasions of fire-dependent ecosystems by exotic woody plant species can disrupt fire cycles and alter successional trajectories. Prescribed fire is an important tool for managing such ecosystems, yet the role of top-down processes in mediating fire effects on invasion remain poorly understood. Fire may influence exotic woody plant species through its indirect effects on granivore activity. Given the importance of habitat structure for determining granivore activity, I focus on the role of fire-induced habitat variation at the between-habitat and landscape scales. I quantified seed removal for four species of woody exotic plants (Elaeagnus umbellata, Albizia julibrissin, Triadica sebifera, and Melia azedarach), in longleaf pine savanna that varied spatially in time since fire, in the Sandhills of North Carolina. I selected eight sites burnt one growing season prior, and nine sites burnt three growing seasons prior, within which I established paired plots in upland plant communities, which included Pinus palustris, Aristida stricta, legumes, grasses, and composites (hereafter “upland habitat”), and upland-wetland ecotone communities, which included P. palustris, Acer rubrum, Liriodendron tulipifera, shrubs, cane, and forbs (hereafter “ecotone habitat”). Over two 15-day periods, seeds were presented in depots that allowed either arthropod, or arthropod and small vertebrate access. Overall removal levels for the two presentation periods were 8.81% and 8.65%. For all exotic plant species, removal was highest in ecotone habitat, which had greater understory vegetation cover and litter depth than upland habitat. For three of four species, seed removal was highest in ecotone habitat three growing seasons post-fire. While granivores removed seeds of all four species of exotic plants, E. umbellata experienced significantly higher removal than other species, suggesting that granivores exhibited seed selection. Allowing vertebrate granivores access to seeds enhanced seed removal and this effect was influenced by habitat type. These findings suggest that ecotone habitats in this system experience greater seed removal than upland habitats, particularly as time since fire increases and understory vegetation recovers. Such differences in seed removal percentages, together with seed selection, may contribute to variation in the success of exotic invaders in fire-dependent longleaf pine savannas.
Issue Date:2013-02-03
Rights Information:Copyright 2012 Jacqueline Krall
Date Available in IDEALS:2013-02-03
Date Deposited:2012-12

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