Semester

Spring

Date of Graduation

2008

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wood Science and Technology

Committee Chair

David W. McGill.

Abstract

This document discusses three fire and exotic invasive plant related research studies that were conducted in an area of the Ridge and Valley dominated by xeric mixed-oak and oak-pine forest communities. The first study characterizes the timing, frequency, and magnitude of canopy disturbances in the study area by investigating demographic (age distributions), anatomical (growth increment patterns), and structural (diameter distributions) evidence. In addition to the general reconstructed disturbance history, the potential link between overstory tree-of-heaven (Ailanthus altissima (P. Mill.) Swingle) populations and prior forest management disturbances (i.e. harvesting) is investigated. This study indicates an uneven-aged structure resulting from multiple disturbances of varying intensities throughout the area. One study area-wide disturbance event was identified around the turn of the 20 th century. The majority of the areas where tree-of-heaven has ascended into the main canopy are either in harvested areas, or along roads. Native ground-layer vegetation around the main tree-of-heaven stems is in danger of being severely impacted by vegetative reproduction.;In the second study, the relationship between plot-level three-year post-fire bole scorch height, or stem-bark char, parameters (independent variables) and other fire intensity variables (litter consumption, thermocouple temperature, and sapling mortality) are investigated. This study indicates that neither overstory nor sapling bole scorch height variables are significantly related to thermocouple temperature measurements. The sum of the sapling scorch heights is significantly related to litter consumption, but only accounts for 11 % of the variation. However, all bole scorch height variables are significantly related to sapling mortality one growing season after the fire. This further illustrates the usefulness of scorch height as an estimator of relative fire intensity.;The third study examines the effects of a prescribed fire on understory exotic invasive plants. In this study, several analytical methods were employed to determine if: (1) abundance and importance increased following the fire, (2) relative fire intensity played a role, and (3) environmental variables were related to populations. The results indicated that only one species, tree-of-heaven, showed significantly higher abundance and importance following the prescribed fire. The results also implied that moister areas, where understory species richness was higher and where relative fire intensity was lower, provided a favorable microsite for the exotic invasive species. Furthermore, environmental factors played more of a role than relative fire intensity in determining the probability of presence of exotic invasive plants in the understory.

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