Forest Inventory and Analysis Data Helps Inform Landscape Drivers of Insect-induced Tamarack Mortality
Tamarack trees have long been associated with Minnesota’s “Great North Woods.” Though no longer as prevalent across the landscape as before European settlement, tamarack in Minnesota has seen a slow but steady rise in abundance starting in the mid-20th century. Now, an eruption in the population of native eastern larch beetles (ELB) is causing mortality of tamarack to climb. Unlike historic outbreaks, the current ELB outbreak has been long lasting and was not preceded by disturbance events, including defoliation or flooding. Comparing the growing conditions and tree characteristics of live and dead tamarack trees, Forest Service scientists and their research collaborators found that the largest diameter trees were more often killed by ELB in the northeastern portion of Minnesota. In northwestern Minnesota, tamarack trees growing close to other conifers (as opposed to hardwoods) were more likely to be killed by ELB. Comparing tamarack trees across a vast area provides an opportunity to better understand factors that make trees more susceptible to bark beetle mortality on a landscape-scale. Knowing what types of trees or what growing conditions make tamarack trees more susceptible to mortality from ELB will help to inform land management strategies necessary to reduce the impacts of this insect.
Forest Service Partners