Tree regeneration ecology and herbaceous layer dynamics of an old-growth central Appalachian forest

Date of Award

2012

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Advisor: Ryan W. McEwan

Abstract

Diversity and compositional dynamics in deciduous forests of eastern North America are subject to a suite of potentially interacting ecosystem drivers, including, but not limited to, anthropogenic and natural disturbances, fire, exotic species invasions, climate shifts, and environmental gradients. The structurally complex Eastern Deciduous Forest is one of the most diverse temperate ecosystems, and despite decades of ecological research, many fundamental questions regarding spatial and temporal dynamics are either hotly debated or remain unanswered. The body of work presented in this thesis is part of an ongoing long-term botanical analysis of Big Everidge Hollow, a watershed containing old-growth forest within the Lilley Cornett Woods Appalachian Research Station on the Cumberland Plateau of eastern Kentucky. The relatively pristine condition of this site has provided a unique opportunity to study forest dynamics in an area of minimal anthropogenic disturbance. The first chapter of this thesis describes changes in the floristic community that have occurred since the last floristic survey of the site in 2001. Twenty-three new species records are reported, some of which are invasive species that pose a threat to the biological integrity of the site. The second chapter examined baseline dynamics of woody understory over a decade, described the relationships between diversity and surrogate measures of productivity (density and cover), and investigated the reaction of shrub- and ground-layer vegetation to a recent fire in one portion of the study site. Decadal oak-maple dynamics in the woody understory of this old-growth stand did not fully support the hypothesized oak-to-maple dominance shift thought to be occurring in forests across eastern North America; changes in shrub- and ground-layer populations of maple (Acer spp.) were erratic while oak (Quercus spp.) populations appeared stable. Unimodal relationships between diversity and productivity surrogates were found in both woody understory layers and are likely driven by the range of environmental conditions found within the study site. Fire induced short-term changes in the shrub- and ground- layers and may have facilitated colonization of invasive species. The third chapter aimed to understand how spatial patterns of both alpha and beta diversity in the herbaceous layer relate to topography and how these relationships vary over time. Shannon diversity varied linearly with aspect and slope, but unimodally with elevation, indicating steep, mid-elevation, and south-facing plots tended to be most diverse. These relationships were persistent, but weakened slightly, through the growing season. Significant spatial species turnover occurred across topographic gradients; compositional dissimilarity tended to be greater between plots with greater differences in aspect, slope, and elevation. Full-season temporal species turnover (i.e. compositional change over time) was weakly related to aspect (linear fit) and elevation (quadratic fit; r2 = 0.09, P < 0.05), suggesting greater species turnover occurred on north-facing and mid-elevation plots. The results presented here fit into a larger body of work conducted at this study site, which has the potential to serve as a model system to provide the necessary baseline knowledge for advancing ecological theory and developing conservation strategies.

Keywords

Vegetation surveys Kentucky Letcher County, Forest regeneration Kentucky Letcher County, Old growth forests Kentucky Letcher County, Ecological surveys Kentucky Letcher County, Botany Kentucky Letcher County, Appalachian Region Environmental conditions

Rights Statement

Copyright © 2012, author

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