Long-term Demography Study of Trillium pusillum var. pusillum Following Hurricane Hugo in 1989

Abstract

ABSTRACT Hurricane Hugo was a category five storm in September of 1989 that significantly impacted natural areas along the Carolina coastal plain through wind damage and storm surge flooding. Francis Beidler Forest, an Audubon wildlife sanctuary in Four Holes Swamp, suffered severe damage to its forest canopy. In response to concerns that the rare spring ephemeral Trillium pusillum var. pusillum may be negatively impacted by the loss of the mixed hardwood canopy, we established permanent plots in the spring of 1990 with single leaf, triple leaf, and flowering individuals recorded by Ecology faculty and students at The Citadel. Disruption to the forest canopy would significantly alter forest floor microhabitat conditions negatively affecting T. pusillum var. pusillum population demography. There was no expected negative effect of Hurricane Hugo, and the loss of canopy cover on the population. Evidence suggests that the decrease in canopy cover and increased light was associated with increased flowering. The coefficient of variation, as a measure of cohort variability among years, increased from flowering, to triple leaf, to single leaf across the 29 years of population monitoring. There was a significant positive association between the number of named storms in the previous two and three years and the number of single leaf plants. There was no evidence that the population is decreasing, even though the number of flowering individuals has decreased. The results of this long-term demography suggest that even severe natural disturbances, like hurricanes and tropical storms, may have a positive effect on Trillium population dynamics.