Chapter Twelve - Insect defoliators as periodic disturbances in northern forest ecosystems

Abstract

Insect defoliators constitute a distinct class of forest disturbance because they are selective, extensive, periodic, and spatially synchronous, albeit imperfectly. This chapter discusses the nature of the mechanisms that generate cycles and synchronize these cycles across the landscape. A template is presented that could be used to structure a process-oriented insect disturbance model and a tritrophic herbivory model of cycle induction is applied to four systems: forest tent caterpillar, western spruce budworm, spruce budworm, and jack pine budworm. All four systems can be interpreted within the context of the same tritrophic regulatory structure and show that the ecological relationships between the defoliating insect, its resource, and its natural enemies are critical processes governing insect-caused disturbance.