Dissertation

Effects of experimental invasive communities on forest dynamics

Galbraith-Kent, Shannon Lee

2008

Overview

Alien invasive plant species have altered the historical descriptions of eastern U.S. forests. This dissertation used an invasive tree ( Acer platanoides) and shrub species (Berberis thunbergii ) to examine how experimental understory communities affected dynamics in a suburban deciduous forest in Central New Jersey, USA. With invasive plant removal often an unrealistic option, these community treatments (0%, 25%, 50% invasive) served as proxies for possible management outcomes to test invasive effects on native species. After only 3 growing seasons, both an A. platanoides canopy and A. platanoides saplings had strong negative impacts on native sapling and seedling growth. There was such a strong negative effect of the invasive canopy on native sapling growth that the presence of invasive saplings was less important. However, beneath a native canopy, native saplings grew significantly more in the absence of invasive saplings. Even if invasive removal in the understory were only done every 2-3 yrs, this would give native saplings release from invasive competition and time to increase in growth (Chapter 1). In two separate experiments, an invasive canopy negatively affected native seedling growth in the forest (Chapter 3), and soil collected from beneath an invasive canopy reduced native growth (greenhouse, Chapter 2). While the understory and canopy types impacted native saplings and seedlings, A. platanoides was largely unaffected (Chapters 1, 3). However, it does appear that it has the ability to shift resource allocation depending on soil type, which may give it a growth advantage over native species (Chapter 2). I did not find support of the ERH, as leaves from seedlings of A. platanoides and A. rubrum had equivalent amounts of herbivory (Chapter 3). In a litter decomposition experiment (Chapter 4), two invasive species had lower C:N ratios than the native species. Higher nitrogen content in invasive litter could alter soil nutrients and cycling and, perhaps, leave a legacy of invasive impact. Experimental studies done in the field can help us increase our understanding of invasive and native species interactions, while providing us with information to guide restoration and management decisions to retain native diversity.

• Publisher: ProQuest Dissertations & Theses
• Subject: Ecology
• ISBN: 9781109191806, 1109191804