PARENT SESSION
Symposium 15: Severe Insect Outbreaks in North American Forests: Recent Trends, Long-Term Recurrence, and the Role of Climate
Organized by: D Gavin and M Ayers
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Chatham Ballroom C.
Spatio-temporal dynamics & landscape ecology of spruce budworm disturbances & the implications for a changing climate.
FLEMING, RICHARD*,1, CANDAU, JEAN-NOEL2, 1 CANADIAN FOREST SERVICE, SAULT STE. MARIE, ONTARIO, CANADA2 ONTARIO FOREST RESEARCH INSTITUTE, SAULT STE. MARIE, ONTARIO, CANADA
ABSTRACT- The spruce budworm (SBW) represents a dominating disturbance factor in North America's boreal forests and during outbreaks trees are often killed over vast areas. This extensive tree mortality constitutes an important fire hazard and shifts the forest toward younger age-classes which contain less biomass (and sequester less carbon). We developed spatially explicit regression tree models from Ontario's historical records to describe how climate and forest structure have influenced defoliation patterns. When climatic predictions corresponding to the next outbreak (2003-2038) were input, the models forecast a general northward extension and intensification of defoliation, with defoliation declining in southeastern, and particularly in southwestern Ontario. To understand how climate affects post-outbreak fire hazards, we studied the fire and defoliation records for the 19,950 km2 experiencing both wildfire and SBW defoliation. Analysis of the spectra of time lags between the two disturbance types indicated that fires occurred 3-9 years after an outbreak disproportionately often. This "window of opportunity" for wildfire starts later after SBW outbreak and lasts longer in western than in eastern Ontario. In addition, 7.5% of the areas containing SBW killed trees were burnt in western compared to 4.8% in eastern Ontario. We suggest that these geographical differences result at least partly from slower decomposition of dead fuels in the drier climates of western compared to eastern Ontario.
Key words: forest fire-insect interaction, choristoneura fumiferana, climate change