Putting more fuel on the fire… or maybe not? A synthesis of spruce beetle and fire interactions in North American subalpine forests

Abstract

Disturbance interactions can create compound, novel effects across landscapes compared to individual disturbance events. However, little consensus exists regarding which mechanisms are important for controlling the interaction of two disturbances with similar climatic forcings in subalpine spruce–fir forests. We synthesized existing primary literature to categorize the potential mechanisms controlling the interactions between spruce beetles and fire. We categorized mechanisms as either substrate mediated or environmentally mediated. Most research investigating the interaction between spruce beetle outbreaks and fire focuses on substrate mediation. There is a need to expand investigations of environmental mediating mechanisms due to the importance of climate and the ability for either disturbance to alter microclimatic conditions. Environmentally mediated mechanisms may better elucidate the interactions between spruce beetles and fire than substrate mediated mechanisms because both disturbances require specific environmental conditions, and both can alter environmental conditions that favor a second disturbance. Our understanding of how these mechanisms promote or constrain interactions is limited and warrants future study. Investigating these topics and expanding the scope of research both spatially and temporally may identify additional patterns that increase the predictability of this important disturbance interaction.