The stand level risk of defoliation and mortality due to the spruce bud-worm (Choristoneura fumiferana, SBW) is linked to the host species con-tent such that stands dominated by the primary host species, balsam fir,are considered the most vulnerable. At the landscape scale there is little information but some work suggests that risk may decrease when landscapes are dominated by secondary hosts, such as black spruce or when landscapes are fragmented. We estimated the relative risk of different landscape structure and species composition patterns on the onset and risk of mortality of an outbreak of the spruce budworm in Quebec, Eastern Canada.
Results/Conclusions
Our results show that initial defoliation risk, or onset, is reduced in non-homogeneous landscapes with a complex mosaic of species including secondary hosts and hardwood non-host species. Progression from initial defoliation to mortality is associated with associational resistance effects from non-host and dilutional effects from secondary host species, with biotic composition factors being more important than physical fragmen-tation effects. Maintaining tree diversity across forested landscapes would improve SBW related mortality outcomes.
