Date of Graduation

7-2015

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Johnnie L. Gentry

Committee Member

Kimberly G. Smith

Second Committee Member

Steven L. Stephenson

Keywords

Biological sciences, Alliaria petiolata, Invasive species, Non-native earthworms, Ozark plateaus

Abstract

Invasive species are widely recognized as organisms that severely alter ecosystem processes in the habitats to which they are introduced. Alliaria petiolata is one of the most important invasive plants in forests of the northern United States. This study examined the geographic distribution of the plant in the southern Ozarks, as well as the effect that it may be having on natural processes within forests of the region by comparing plant species richness, plant cover, and soil properties in invaded and non-invaded plots. It was found that A. petiolata is not significantly altering species richness, cover, or soil properties in the region, and this may be due to the fact that infestations were only about 1% as dense as those in forests of the northern United States. Populations of A. petiolata in the Ozarks were sampled to determine survivorship, fecundity, and preferred habitat types of plants in these forests. This study found that overall mortality of A. petiolata was 93.0%, with the highest mortality occurring between seedling and rosette stage (92.3%). Winters in this region are sufficiently mild enough to allow for very low rosette mortality (0.7%) compared with forests in the northern United States, and this may point to future infestations that rival those in northern forests. Adult plants averaged 70.3 ± 20.5 cm tall and produced an average of 2.1 ± 1.7 stems, 33.5 ± 45.6 siliques and 406 ± 670.8 seeds. Populations sampled in floodplain forests had higher densities of plants at each life stage, experienced higher overall survival rates, and were more reproductively successful than populations sampled in upland forests. Plots were also sampled to determine whether or not non-native earthworms were correlated with increased A. petiolata density. Although earthworm biomass and leaf litter cover were not significantly different between invaded and non-invaded plots, overall non-native earthworm biomass comprised 95.5% of the total biomass sampled, which indicates that non-native earthworms may be displacing native earthworms in disturbed floodplain and upland hardwood forests of the southern Ozarks.

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