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

Master of Science (MS), Ohio University, 2008, Environmental Studies (Arts and Sciences)

The Edge of Appalachia (EOA) Nature Conservancy preserve in Adams County, Ohio hosts many rare and sensitive species which are threatened by an invasive tree species, Ailanthus altissima. Through mapping populations of A. altissima, characterizing abiotic factors correlated with these populations, and examining land-use history, a management plan was created for A. altissima at the EOA. A survey of juvenile growth rates of A. altissima was also conducted to investigate its competitive ability to outpace the vertical growth of native hardwood saplings. In 2006, 12 20 × 50m A. altissima plots and 12 control plots were sampled. Locations of all plots were mapped and data were synthesized in a GIS database. The fastest-growing native hardwood species had much lower growth rates than A. altissima. Minor differences were found between A. altissima and control plots for soil moisture, soil pH, and soil texture. Stand structure was similar between A. altissima and control plots: vegetation area index, percent canopy openness and the percentage of understory cover. These results strongly suggest that A. altissima has the potential to invade most areas of EOA.

Committee: Kim Brown (Advisor) Subjects:

Master of Science (MS), Ohio University, 2007, Environmental Studies (Arts and Sciences)

Ailanthus altissima Miller [Swingle] (tree of heaven) is a non-indigenous invasive plant that is aggressively competing with native vegetation throughout most of the United States. Proper management of this tree is required to protect and maintain biodiversity and ecological processes in the forests. I explored several possible methods to manage the spread of this invasive species, including herbicide injection, prescribed fire, and the combination of herbicide injection and prescribed fire. Additionally, I evaluated the potential for herbicide translocation from injected trees to neighboring non-injected woody species. Herbicide injection with imazapyr not only produced 100% mortality in the targeted A. altissima, but it also translocated and produced mortality in 17.5% of neighboring trees within 3 m. Herbicide injection with glyphosate killed small and medium-size trees, but it was not effective in killing large trees. Prescribed fire alone killed the above-ground stems, but the resprouts returned the stem density to the same pre-fire levels. Accordingly, fire is not recommended as a control strategy for A. altissima.

Committee: Brian McCarthy (Advisor) Subjects: Agriculture, Forestry and Wildlife