Interaction of disturbance agents on Norway spruce: A mechanistic model of bark beetle dynamics integrated in simulation framework WINDROT

Interaction of disturbance agents may cause cascading effects in forests. The three most important disturbance agents of Norway spruce (Picea abies) in northern Europe are Heterobasidion root rot, wind and the European spruce bark beetle (Ips typographus). In this study, we present a mechanistic individual agent based model to simulate the dynamics of the bark beetle and integrate it in the simulation framework WINDROT to further study the interactive dynamics of root rot, wind and bark beetles. We carried out model performance analysis concluding that the model is sensitive to the parameters of optimal bark thickness for reproduction. Stand level interaction between wind and bark beetle disturbances was also evaluated against field data. The stand level simulations show the interaction between the disturbance agents; the root rot increases wind disturbance and bark beetles benefit from wind fallen trees. No direct interaction was found in the simulation study between the root rot and bark beetles. Further experimental research and large scale simulation studies are needed to better understand the underlying mechanisms in the interaction between the disturbance agents.