Pignut hickory (Carya glabra) recruitment failure on a Georgia barrier island
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Authors
Keen, Eric
Issue Date
2008-05-01
Type
Thesis
Language
en_US
Keywords
maritime forest , herbivory , pignut hickory , St. Catherine's Island
Alternative Title
Abstract
Demographic disruption in pignut hickory (Carya glabra) populations, a major canopy species, was
observed for 10 years on St. Catherine’s Island, GA., and recruitment failure was identified as the central
mechanism of local extinction. From 1996 to 2006 there was no recruitment by hickory seedlings into the
sapling size class. Tree cores of the youngest adult trees indicate that there has been no recruitment at the
study site for over 65 years. Tree cores in 4 other pignut hickory populations indicate similar patterns
across the island. Field evidence of browse and a strong statistical relation (p<0.0001) between seedling
density distributions and microsite protection from herbivory suggest that this trend in recruitment failure
is related to the increasing abundance of deer and pigs on the island. Using a size class population
projection model, we estimate that, if such recruitment failure and mortality rates continue, these hickory
populations will be extirpated from the maritime forest within 200 years. The decline of this major
canopy species will have extensive ecological implications. This study points to the high susceptibility of
many hardwood tree species to the current biotic and abiotic conditions that are met within maritime
forests on islands with a continuing history of land use.