Studies of secondary seed dispersal by small mammals have largely been focused
on the interaction between nut-bearing tree species and sciurid rodents such as squirrels,
and on heteromyid rodents in the southwestern United States. However, there is now
evidence that wind-dispersed tree species such as pines also undergo a process of
secondary seed dispersal, where animals redistribute (cache) seeds that have already
fallen to the ground, often in microhabitats more suitable for successful seed germination.
In Florida sandhill, where fire suppression has threatened wind-dispersed longleaf pine
(
Pinus palustris) by encouraging the encroachment of hardwoods such as sand live oak
(
Quercus geminata), secondary seed dispersal may be an important factor in determining
community composition and persistence of longleaf pine systems. Using a combination
of seed depots and seed predator exclosures, I looked at both longleaf pine and sand live
oak in terms of whether small animals such as squirrels (
Sciurus carolinensis) and cotton
mice (
Peromyscus gossypinus) cache the seeds, and where the seeds of these two tree
species best germinate. Since sand live oak acorns are prone to infestation by weevils
(
Curculio spp.), I also examined whether nut condition affects acorn germination
potential. I found that longleaf pine seeds are cached by small mammals to a small
degree. While these seeds are not moved great distances from where they originate, they
are often redistributed into microhabitats that promote successful seed germination.
Caging experiments indicated that seeds were most likely to germinate when buried in
open areas between adult trees, and to some degree, under shrub cover. On the other
hand, sand live oak acorns appear to face heavy predation by large seed predators such as
raccoons (
Procyon lotor) and wild pigs (Sus scrofa). Those acorns that do escape
predation, including weevil-infested acorns, may provide an opportunity for seedling
establishment. However, it appears that sand live oak depends heavily on vegetative
sprouting for regeneration. This suggests that even in the absence of fire, longleaf pines
in Florida sandhill are able to persist through secondary seed dispersal by small animals
coupled with heavy seed predation on competing sand live oak.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-5075 |
| Date | 06 April 2006 |
| Creators | Ansley, Shannon Elizabeth |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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