Doctoral Dissertations

Date of Award

8-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Geography

Major Professor

Henri D. Grissino-Mayer

Committee Members

Sally P. Horn, Carol P. Harden, Wayne K. Clatterbuck

Abstract

Disturbance is a natural part of any forest ecosystem. When disturbance regimes are altered, the forest stands will reflect those changes. Southern Appalachian xeric pine-oak woodlands are one forest type that has experienced such change, primarily in the form of fire suppression. The western side of Great Smoky Mountains National Park contains stands of large trees that escaped earlier intensive logging, show evidence of past fire, and provide an ideal setting for reconstructing stand histories. For three lower-elevation (ca. 500 m ASL) study sites, I used crossdated yellow pine tree-ring chronologies and records from cross-sections taken from living and dead pines to reveal historical patterns and relationships of wildfire, climate, and human activity. Cores and vegetation data collected at three 20 x 50 m plots per site provided age structure, stand structure, and stand composition. All three chronologies displayed a high degree of sensitivity to yearly environmental fluctuations and extended back through the 1700s. Yellow pine growth was strongly and positively correlated with winter temperatures, which were primarily influenced by the North Atlantic Oscillation. The tested climate variables displayed relationships that appeared to shift over time, or across an ambiguous boundary on which the park resides. Climate oscillations in both the Atlantic Ocean and Pacific Ocean modulated wildfire frequency and events. Wildfire events occurred frequently prior to park establishment in 1934 and were primarily anthropogenic in origin. Most fires burned during dormancy or early in the growing season, but widespread and more recent fires tended to occur later. Fire frequency peaked in the 1800s with an average return interval of two years. Absence of wildfire during suppression was associated with establishment of fire-sensitive species, such as red maple and eastern white pine. Yellow pine regeneration was weak and dominated by Virginia pine. Results from this study can be used by park personnel to plan and manage fires to restore ecosystem processes to a pre-suppression state. The chronologies provided three centuries of data that can be used to reconstruct climate variables and to enhance our understanding of climate dynamics.

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