Regeneration of quaking aspen (Populus tremuloides) after fire risk reduction treatments

Abstract

Quaking aspen (Populus tremuloides Michx.) is a keystone species in the western US, and typically requires high-severity disturbance (historically stand-replacing fire) to regenerate and maintain population health when coexisting with conifers. Aspen forests are declining due to fire suppression, herbivory, and drought, and restoration is a priority for many forest managers. Prescribed fire and harvest are currently the only fuel reduction treatments in practice, imposing limitations on land managers. A mechanical treatment method, called ‘roller-felling,’ has been developed to mimic stand-replacing fire by reducing fuel loading and resetting succession of late-seral stage, conifer-dominated, aspen communities. We examined the ecological impact of roller-felling by investigating factors contributing to post-treatment aspen regeneration, ultimately determining the feasibility of this method as an alternative, stand-replacing disturbance treatment. Specifically, I quantified aspen regeneration stem densities to determine if the result emulated stand-replacing fire. I also measured other metrics of treatment “success”, with additional factors influencing aspen regeneration, including the ratio of suckers to true seedling establishment, ungulate browsing pressure, and herbaceous understory diversity before and after treatment. Preliminary, single-growing season, results indicate densities exceed threshold-related objectives, while related ecological impacts remain less conclusive. A second year of sampling in this upcoming field season will allow for more definitive, short-term results on the comprehensive, ecological impact of roller-felling. This research could allow for widespread application in remote areas where logging is unfeasible and in Wildland Urban Interface areas, where prescribed fire can pose a risk to communities. Additionally, this will set groundwork for long-term monitoring of roller-felled areas, furthering understanding of aspen regeneration dynamics, and will apply to forest and fire management regionally, where goals are to reduce fire risk and maintain aspen communities across the western US.