Factors affecting susceptibility of urban ravine forests to invasion by non-native vegetation

grantor: University of TorontoThe relationship between ravine edge characteristics and the incidence of invasion by nonnative vegetation into local urban ravine forests was identified using plot sampling and multivariate data analysis. Survey data were collected from 41 urban ravine sites across the Greater Toronto Bioregion in 1999. Detrended Correspondence Analysis (DCA) was performed on canopy and ground vegetation for the 166 subplot dataset. DCA indicated that invasive vegetation was highly abundant in disturbed ravine versus mature stable forests. Canonical Correspondence Analysis (CCA) and Detrended Canonical Correspondence Analysis (DCCA) indicated that aspect, adjacent land use type, and edge characteristics were highly correlated with the ground and canopy species composition. Two-Way-INdicator-SPecies-ANalysis (TWINSPAN) clustered similar forest types together based on ground flora that are indicative of disturbed habitats, or exotic species. Results indicate that anthropogenic impacts to ravine forest structure is increasing the likelihood of invasion by non-native vegetation and that top-of-stable bank buffers would alleviate much of the disturbance within these ecosystems.M.Sc.F