PARENT SESSION
Poster Session #39: Disturbance Ecology.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
39
A retrospective analysis to explore the interaction between spruce budworm outbreaks and forest fire activity in Ontario.
Fleming, Richard1, Candau, Jean-Noel2, McAlpine, Rob 3, 1 2 3
ABSTRACT- The dominant natural disturbances in Canada's boreal forests are wildfire and outbreaks of spruce budworm, Choristoneura fumiferana (Clem.). Our research focuses on the spatial and temporal patterns of the interaction of these disturbance regimes at landscape scales and on some of the underlying ecological processes. As a prerequisite to developing models for forecasting, and as a baseline for future monitoring, we present early results from a retrospective analysis of Ontario's historical records over the past 60 years. These results begin to quantify the interaction between SBW outbreak and wildfire disturbance regimes. Spatiotemporal analyses suggest that fires burned less than 10 x 106 ha while SBW caused whole tree mortality within 33 x 106 ha. Within the 41 x 106 ha defoliated by SBW at least once since 1941, the proportion burnt was greatest in areas that suffered moderate frequencies (9-11 years) of SBW defoliation (P=0.00021). Randomization tests revealed that fires over 200 ha occurred 3-9 years after a SBW outbreak more often than would be expected by chance alone (P<0.05), and that SBW outbreaks generally occurred less often than expected by chance alone (P<0.05) between 1 year before and 16 years after fire. This 'time-window' of disproportionately high fire prevalence appears to have started longer after SBW outbreak and to have been wider in western than in eastern Ontario. Climatic explanations for such differences are investigated.
KEY WORDS: disturbance interactions, boreal forest fire, Choristoneura fumiferana, climatic change