THE EFFECT OF EXOTIC SPECIES ON RIPARIAN PLANT DIVERSITY ON CONSERVATION LANDS IN THE GREATER BOSTON AREA

摘要

As part of a long-term ecological research program instituted by the Urban Ecology Institute (UEI) in conjunction with Boston area high schools, we have conducted a research project through the Environmental Scholars Program at Boston College. We have investigated plant diversity at several conservation sites in the greater Boston area. These sites are significant to the educational programs administered by the UEI and the majority of them are also part of the Charles River watershed. At each site we investigated the effects of invasive exotic plant species on the biodiversity of the site. Our goal was to see if exotic plants were having an impact on diversity through an investigation that did not involve time series data and to create a baseline to investigate this issue over the long term. Five fifteen-meter transects were laid out at each site. The transects were spaced evenly along the length of the river defined as the "site". All plants falling within .5m of the transect line were identified and counted. Linear regressions were conducted to analyze the effects of exotic species on the overall composition of the plant communities. Although exotic species were found at all sites, including some highly invasive species such as Phragmites (Phragmites australis) and Purple Loosestrife (Lythrum salicaria), no evidence was found to suggest that exotic species significantly reduced the diversity of native plants. There was a slight (not statistically significant) inverse correlation between the number of exotic plants and the number of native plants, but not between the numbers of exotic plants and the number of native species present. Our data represent a snapshot in time that we expect will serve as the basis for the long-term studies being carried out at these sites.