Date of Award:

8-2023

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 forests are important communities in the western United States where they provide preferential food and habitat for animals, limit wildfires from spreading, and have favorable aesthetics, among other things. Their putative decline is an issue for ecology and management. We remeasured the aspen population on Cedar Mountain, Utah, to assess changes to its condition since it was originally surveyed in 2008. We found that the area comprised of stable aspen (>80% aspen) decreased from 84.3% to 69.7%. The amount of mortality has increased slightly over the last decade, but crown dieback has stayed virtually identical. Additionally, the intensity and frequency of insect and pathogen damage have increased significantly. The amount of aspen in the understory has increased, resulting in more of the landscape exhibiting levels of regeneration sufficient for aspen to be self-replacing. While the ratio of overstory to understory aspen was identical between sampling periods, the amount of sapling-sized trees recruiting to the overstory increased. The extent of browsing of understory aspen has also decreased. Extant aspen forests are increasing in age, and relative density indicates the landscape is further senescing. If the amount of aspen mortality is not matched or surpassed by the amount of regeneration and recruitment, the aspen forest type will likely continue to reduce in area and/or be converted to conifer forest or non-forested land. Measuring and assessing changes to the structure, composition, crown condition, mortality, damage presence, regeneration and recruitment level, and browsing pressure of this aspen population improves our understanding of potential causes and factors involved in reductions to aspen forests in southern Utah. This understanding can inform aspen forest management and provide insight into aspen forest dynamics, generally.

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