Biotic disturbance agents in the boreal forest: considerations for vegetation change models

Disturbance regimes strongly determine vegetation patterns and succession i n the boreal landscape. One of the current challenges for boreal vegetation modellers is to represent disturbance agents as dynamic factors that can r espond to climate change. Outbreak species of insects and plant pathogens c an cause marked changes in vegetation patterns and should be incorporated i nto vegetation change models. This introduction to the ecology of boreal bi otic disturbance agents is designed as a brief overview for global change r esearchers and modellers. We discuss the importance of biotic disturbance a gents in the boreal forest, offer an overview of their ecology, and review modelling approaches. We illustrate these issues with examples from differe nt systems, drawing largely from our experience with bark beetles.