Forest ecosystem responses to interacting bark beetle and fire disturbance

Document Type


Journal/Book Title/Conference

American Geophysical Union

Publication Date

Winter 12-2019


From 2003 to 2012, bark beetles accounted for 32% of observed tree mortality in the western United States. The spatial extent of this epidemic, paired with predicted climate conditions that likely lead to increases fire frequency and severity, necessitate an increased understanding of the synergistic effects of bark beetle mortality and subsequent fire on ecosystem processes. Fires in previously beetle-affected forests are typically characterized by a highly heterogeneous distribution of burn severity, thus providing a unique opportunity to understand the physical and biological processes that control the water, carbon, and nitrogen cycles within a forest ecosystem following sequential and interacting disturbances. The 2018 Badger Creek fire burned more than 21,000 acres of subalpine lodgepole pine forest in southeastern Wyoming, including parts of the AmeriFlux Chimney Park (US-CPk) flux tower site that had been collecting post-beetle ecosystem recovery data since 2008. By re-instrumenting the site with sap flow sensors, time-lapse electrical resistivity tomography geophysical imaging, and five eddy covariance stations, we quantified carbon and water fluxes in relation to post-beetle fire intensity (beetles without fire, beetles followed by understory fire, beetles followed by stand-replacing fire). We further partitioned these fluxes into contributions from understory, overstory, and soil and assessed the interactive effects between post-beetle fire and vegetation regrowth. Results show clear differences in timing and characteristics of carbon and water fluxes, as well as in belowground water dynamics between post-beetle fire intensities in the first year following the fire. A strong regeneration pulse of lodgepole pines was found in both fire-affected sites. Our results will improve predictive models of carbon and water dynamics in future disturbance scenarios in forests that will be characterized by increasingly interactive disturbance regimes.