Date of Award

12-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Wildlife and Fisheries Biology

Advisor

Conner, William H

Committee Member

Guynn , David

Committee Member

Song , Bo

Committee Member

Montague , Clay

Abstract

Substrate disturbance by wild pigs ( Sus scrofa L.), mainly wild pig rooting, was evaluated bi&ndashmonthly over three years in fixed 1,000 m2 plots at Congaree National Park, South Carolina, USA. The study compared hog substrate disturbance among four habitats: three mature wetland floodplain forest types (mixed bottomland hardwoods, cypress&ndashtupelo swamp, seepage floodplain forest), and successional upland pine flatwoods adjacent to the floodplain (including former pine plantation). New disturbance included fresh signs of hog substrate disturbance. Total disturbance included both new and older hog disturbance still visible on the landscape (equivalent to all disturbance that would be recorded under less frequent sampling). Hog disturbance, across all years, was more abundant in cypress&ndashtupelo (10% new disturbance; 19% total disturbance) compared to bottomland hardwoods (4% new disturbance; 9% total disturbance) and seepage forest (2% new disturbance; 9% total disturbance); all floodplain forests had greater disturbance than pine flatwoods ( Concurrent with the 1,000 m2 plot study, ground cover and understory vegetation were examined using 0.25 m2 quadrats. In the absence of recent rooting, floodplain habitats had higher vegetation cover (30&ndash43%), lower leaf litter cover (57&ndash69%), and greater species richness (5&ndash8 species) compared to pine flatwoods (4% vegetation cover, 95% leaf litter cover, 3 species). In recently rooted areas, vegetation (1&ndash14%) and leaf litter (30&ndash57%) cover were lower than in areas without recent rooting, and were similar among habitats, with high bare soil cover (42&ndash54% vs. 0% without recent rooting). Species richness was still greater for the floodplain (4&ndash8 species) versus flatwoods (2 species) with recent rooting. Low herbaceous cover values in pine flatwoods were attributed to former agricultural and pine plantation management and lack of fire, likely influencing the minimal hog disturbance levels observed in pine flatwoods. Herbaceous cover values in bottomland hardwoods (36%) and cypress&ndashtupelo (30%) were higher than expected, especially for cypress&ndashtupelo, which typically has little understory. Herbaceous cover on the floodplain may have been related to a combination of drought, draw down, forest tent caterpillar canopy defoliation, long&ndashterm pig rooting, and Hurricane Hugo. Recently rooted areas had greater association with coarse woody debris (CWD) (29% incidence) than areas without recent rooting (8%). Pig rooting in and around downed logs and snags likely relates to microhabitat selection and potential food/prey resources. Bottomland hardwoods, unexpectedly, did not have overall greater plant species richness or diversity than cypress&ndashtupelo. Also unexpectedly, recently rooted areas were not generally less diverse than areas without recent rooting. Within habitat, recently rooted bottomland hardwoods had lower species richness and diversity than areas without recent rooting; however, recently rooted cypress&ndashtupelo had greater species richness and similar diversity, and seepage forest had greater diversity, than areas without recent rooting. Seepage forest with recent rooting had the most diverse understory among all combinations of habitat and rooting. Pig rooting may act as a periodic disturbance, contributing to species richness and diversity in some habitats. Within seepage forest, these results might also relate to microhabitat selection by pigs for small wet depressions with more abundant and diverse herbaceous cover. If pig rooting creates, enhances, or maintains depressions in seepage forest, pigs may both influence the understory vegetation and respond to it as well. Habitat had a stronger influence on understory species composition than recent rooting. This may be due to differences in hydrology, landforms, and soils; as well as long&ndashterm pig rooting, which likely influences the entire floodplain over time. Within habitat, differences in species composition for areas with and without recent rooting were limited to seepage forest (with possible microhabitat selection by pigs). Recent rooting may also have a homogenizing effect on the understory, lessening cross&ndashhabitat differences. In bottomland hardwoods, pig rooting, forest maturity, closed canopy, and low seed production may limit seedling recruitment, though this could not be evaluated due to a lack of seedlings throughout the study. In cypress&ndashtupelo, dry downs are required for recruitment of bald cypress and water tupelo, as seeds from these species will not germinate when flooded. Despite long&ndashterm drought and dry down, seedlings were not recorded in the plots or quadrats over a three&ndashyear period. Similar to documentation that pigs reduce longleaf pine regeneration, and concerns that rooting may limit bottomland hardwood regeneration, rooting in cypress&ndashtupelo could potentially limit bald cypress and water tupelo recruitment, although the evidence for this is circumstantial.

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