PARENT SESSION
Contributed Oral Session 130: Forest Infestations and Mortality
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal

Spatiotemporal Dynamics of Insect-Fire Interactions.

Lynch, Heather^*,1, Moorcroft, Paul¹, ¹ Harvard University, Cambridge, MA, USA

ABSTRACT- Insect outbreaks and forest fires individually represent significant forest disturbances which have long-term effects on the dynamics and composition of forest ecosystems. Although it has long been speculated that forest fires and insect outbreaks may be correlated, there has been little quantitative evidence of statistically significant spatiotemporal correlations between these two contagious disturbances. To study these problems, we extended traditional methods of spatial statistics to consider space-time correlations between two different disturbance processes. We have analyzed two ecosystems, Yellowstone National Park and British Columbia, for evidence of statistically significant interactions between forest fires and insect outbreaks. Our analysis of western spruce budworm (Choristoneura occidentalis) outbreaks and forest fires in British Columbia for the period 1971-1995 indicates that areas affected by western spruce budworm infestation have a significantly decreased risk of forest fire for 9 years following recorded budworm damage. Conversely, forest fires increase the risk of budworm infestation for the first year and then decrease the risk of infestation for a 2-5 year period following fire. These temporal correlations extend over a spatial range of at least 10 km. Our study rejects the common assumption that insect infestation necessarily results in increased fire risk, and provides a new technique for studying multiple disturbance phenomena which interact in both space and time.

Key words: spatiotemporal interactions, British Columbia, western spruce budworm, fire ecology