Date of Award:

5-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Larissa L. Yocom

Committee

Larissa L. Yocom

Committee

Karen E. Mock

Committee

Owen Burney

Abstract

Quaking aspen (Populus tremuloides Michx.) is an ecologically important forest species in the western U.S. Aspen forests host a variety of understory species, are critical wildlife habitat, and are considered a "natural fuel break" since they are less likely to support crown fires than conifers. Because of climate change and altered disturbance regimes, populations are declining, and innovative strategies are needed to restore aspen. Planting aspen seedlings is a solution, though not a common practice in the West and has been met with high mortality in past experiments. For aspen planting to be more broadly implemented, managers need guidance to increase probability of seedling success. We developed a planting experiment to determine whether specific types of planting sites and conditions in the field could increase the survival and growth of nursery-grown aspen seedlings. The increasing occurrence and severity of wildfire presented an opportunity to plant seedlings in high severity fire footprints. Aspen trees thrive in severely burned landscapes, where conifer regeneration may be limited. We planted 1,140 seedlings, using remnant standing dead trees, snags, and downed logs as nurse structure treatments. We also tested individual tree shelters on half of the seedlings to determine if this is an effective tool to prevent herbivory. After one growing season we assessed seedling survival, causes of mortality, growth, and local competition. In a separate field experiment we also installed soil moisture-sensing probes to monitor soil moisture content at each type of planting site (snag, log, open). My results show high survival overall compared to past experiments, notably in seedlings next to snags. This could be because soil moisture content was high near snags during dry periods. Tree shelters increased the probability of seedling survival but had mixed effects on growth within the one season. The results from this research will contribute to the development of best practices in future aspen seedling restoration projects and suggest a need for snag retention on the landscape after fire.

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