How will aspen respond to mountain pine beetle? A review of literature and discussion of knowledge gaps

There has been speculation that quaking aspen (Populus tremuloides) dominance of forests will increase due to mortality caused by mountain pine beetle (Dendroctonus ponderosae) (MPB). High aspen sucker densities have been observed in the years following MPB-caused pine mortality, but it remains unclear if this disturbance will result in a pulse of aspen recruitment to forest overstories. Many factors will affect aspen recruitment and overstory health. Surviving conifer overstory and advance regeneration will limit available light and other resources, potentially decreasing aspen suckering, growth, and survival. Following the creation of MPB-caused canopy openings, mortality rates of overstory aspen may increase due to exposure or damage by falling snags. Severe browsing damage may prevent suckers from successfully recruiting to the canopy where there are high domestic and/or wild ungulate densities, even where forest conditions promote aspen recruitment. Climate and weather variability will also mediate aspen response to MPB. Research that focuses specifically on effects of MPB-caused forest structure changes on aspen suckering, recruitment, and overstory health, and the potential for browsing and climate to interact with these effects, is needed to inform our understanding of how MPB-caused mortality will affect aspen in western North America.

► We review aspen recruitment dynamics and discuss how mountain pine beetle disturbance affects these dynamics.
► We synthesize the limited research addressing aspen and mountain pine beetle mortality.
► We highlight major uncertainties in our understanding of aspen response to mountain pine beetle.