PARENT SESSION
Poster Session #39: Disturbance Ecology.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
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Effects of a moderately severe disturbance on the composition and density of woody seedlings in eastern Ontario forests.
CONTRERAS, THOMAS1, MACKO, SAMANTHA2, FAHRIG, LENORE2, 1 2
ABSTRACT- The influence of a disturbance on plant community composition and structure can occur through a variety of mechanisms. It may produce changes in environmental conditions that influence growth and establishment of seedlings/saplings, cause changes in seed production, or influence seed dispersal. In January 1998, an ice storm struck eastern Ontario, with ice deposition ranging from 40-80 mm over a five-day period. One hundred and ninety-two forest sampling plots, surveyed in eastern Ontario in 1997, were re-surveyed in 1998 and 1999. In 1998, trees in each plot were assessed for damage related to the ice storm. Mean crown loss did not exceed 30% and we observed no tree mortality even though ice accumulation for the single event was twice that of other storms this century. Mean species richness and mean density of woody seedlings differed significantly pre- and post-storm (richness increased while density decreased) (p<0.0001). Differences were also seen between dispersal types, with mean species richness and density of animal-dispersed seedlings increasing and wind-dispersed species decreasing in both richness and density following the storm (p<0.0001). Our results suggest short-term changes in the composition and density of woody seedlings even when disturbances are of low-moderate severity. These changes are related to species life history characteristics with animal-dispersed species increasing in both richness and density following the disturbance.
KEY WORDS: ice, disturbance, dispersal, seedlings