Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Science in Biological Sciences

Department

Biological Sciences

First Advisor

Keith T. Killingbeck

Abstract

The decline in rare plant populations and the decrease in size of their native ranges have led to escalating losses of biodiversity. A combination of shrub cutting and fire was applied to an endangered species "hot spot" in southern Rhode Island, USA to determine the effects of these treatments on a group of eight rare herbaceous plant species exposed to ever-increasing encroachment by tall shrubs. Shrub cutting and fire were also applied to a shrub-dominated area adjacent to the hot spot to determine if it was possible to promote establishment and growth of the rare plants in areas in which they were not found in abundance. My analyses focused on the three rare species that were found in greatest abundance within the rare plant area; Aletris farinosa, Platanthera ciliaris, and Polygala cruciata. Fire appeared to have a positive effect on the reproductive output of the endangered orchid Platanthera ciliaris; the mean density of inflorescences doubled from 0.70 inflorescences/m2 in 2005 to 1.41 inflorescences/m2 in 2006 in plots that were burned. However, this difference was not statistically significant. Significant differences in vegetation characteristics were observed between plots in which rare plants were present and plots in which rare plants were absent. Platanthera and Aletris had negative relationships with woody plant cover, and positive relationships with herbaceous plant cover. The density of Aletris was significantly correlated with the density of Drosera sp. (r=0.73, PCelastrus orbiculatus. The density of Celastrus was an order of magnitude higher in the cut sector than in the control. In an adjacent sector that was both cut and burned, the native shrub Rhus copallinum produced a similar rapid response to the treatment Continued management must now focus on limiting the potential harmful impacts of Celastrus while promoting growth and establishment of the rare plants at the site.

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