Master of Science (MS), Ohio University, 2015, Plant Biology (Arts and Sciences)

Since the loss of Castanea dentata (American chestnut) from eastern hardwood forests, invasive species have occupied many of the forests where chestnut once resided. Even though agencies have begun to replant hybrid chestnuts into the forests, no one has examined how invasive species might interact with American chestnut. In this study, allelopathic impacts on chestnut were mimicked by adding aqueous extracts or biomass of three allelopathic invasive species tree of heaven (Ailanthus altissima (Mill.) Swingle), garlic mustard (Alliaria petiolata (M.Bieb.) Cavara and Grande), and Amur honeysuckle (Lonicera maackii ( Rupr. ) Maxim.)) to soils supporting chestnut seedlings. In greenhouse experiments, chestnut seeds were treated weekly with aqueous extracts of biomass from the invasives. Chestnut seedlings were also planted in gardens and treated with root or shoot biomass from the invasives. Finally, chestnut seedlings were planted in a forest at sites with garlic mustard present and at sites where garlic mustard had been regularly removed for 8 yrs. Growth factors of chestnut, such as height, mass, and basal area, were measured. Chestnut seedlings treated with tree of heaven extracts had lower heights and more re-sprouts than the control groups. However, results were not consistent among the experiments. Chestnut seedlings treated with some invasive plant biomass, including tree of heaven biomass, had heights statistically similar to the control groups. When treated with roots of garlic mustard, chestnut heights were statistically lower than the negative control. Chestnut seedlings planted in garlic mustard plots in the forest were only statistically taller the first time they were measured, but were not statistically different thereafter. The results from these initial experiments suggest that the allelopathic effects from tree of heaven may negatively impact reintroduction of American chestnut; however, other invasives may be less problematic.

Committee: Brian McCarthy Dr. (Advisor); Jared Deforest Dr. (Committee Member); David Rosenthal Dr. (Committee Chair) Subjects: Ecology; Plant Biology

Master of Science (MS), Ohio University, 2012, Environmental and Plant Biology (Arts and Sciences)

Disturbance such as forest management is thought to promote invasive species spread. This study uses population demography to address the spread of the invasive species Ailanthus altissima, Alliaria petiolata, and Microstegium vimineum in forested sites in southeast Ohio. Invasive species populations were examined in the silvicultural treatments prescribed burn and timber harvest, plus control plots with no management. Seed rain, seedling establishment, and the soil seed bank was studied for each population. All invasive seeds formed a persistent seed bank and experienced seasonal dormancy, but the proportion of dormant seeds varied among species (p<0.05). Slope aspect effected seed survivorship and dormancy (p<0.05) for each species. Dormancy for each species showed no relationship or a weak relationship with time since seed burial. Invasive populations expanded at a constant rate among treatments, and invasive seeds changed dormancy conditions seasonally to allow for germination during favorable conditions, which may contribute to invasive ability.

Committee: Glenn Matlack PhD (Advisor); Stefan Gleissberg PhD (Committee Member); Harvey Ballard PhD (Committee Member) Subjects: Botany