Date of Award:

5-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

R. Justin DeRose

Committee

R. Justin DeRose

Committee

Larissa L. Yocom

Committee

Paul C. Rogers

Abstract

Quaking aspen (Populus tremuloides Michx.) is a keystone species that, when coexisting with conifers (i.e., seral aspen), often undergoes stand-replacing disturbances to sustain long term vigor. Historically, mixed-to-high severity fire reduced fuels and regenerated aspen, but such disturbances have become less common in recent decades. This has often led to high fuel loading, and many seral aspen stands are at now risk of an unpredictable, high-severity fire, posing a threat to development in the wildland-urban-interface. The lack of a commercial market for aspen, and the risk of conducting prescribed fire, means there are few alternate management options. This has led to the development of a novel method called roller-felling, a mechanical treatment designed specifically to reduce fuel loading and restart succession of late seral-stage, now conifer-dominated, aspen communities.

This study assessed the short-term impacts (one- and two-year) of roller-felling on aspen regeneration and understory vegetation. We compared metrics of stand composition, structure, and aspen regeneration densities to determine treatment response. Roller-felling eliminated the overstory and resulted in prolific aspen suckering; this corresponded to changes in forb and shrub composition and ground covering of biotic functional groups. Decreased slash retention and scarification of mineral soil promoted aspen regeneration and higher densities of early-successional forbs. Greater slash retention and less machinery traffic reduced aspen regeneration and influenced understory composition, resulting in greater shrub cover and forbs of mid- to late-successional status. Well-established dynamics (e.g., greater aspen prior to disturbance or lessened slash retention promoting sucker densities) of early-successional aspen regeneration were observed, suggesting roller-felling acted as a stand-replacing disturbance and restarted succession, effectively reducing the risk of high-severity fire. This study established a baseline for long-term monitoring of these areas, furthering the understanding early successional aspen ecology, which will have application to forest management regionally, where the goals are to reduce fire risk and promote aspen across western US.

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