Undergraduate Honors Thesis


Long-term Composition of Herbaceous Understory Species in Persistent Piñon-Juniper Woodlands in Response to Fuel Reduction Treatments Public Deposited

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  • Piñon-juniper (“P-J”) woodland cover has increased over 150 percent across the western United States since 1860. The expansion of P-J woodlands results in encroachment onto bordering vegetation types, commonly sagebrush steppe, reducing regional biodiversity and habitat function. Infilling of P-J woodlands has stifled the flow of resources to the understory, resulting in little to no herbaceous cover. Rather, P-J understory is primarily connected patches of woody debris, that have accumulated over decades of alterations to land use and management. Dense fuel beds increase the risk of a crown fire, which pose significantly greater threats to wildlife habitat, infrastructure, and fire fighter safety, than surface fires. To reduce the risk of catastrophic wildfire and restore ecological function, P-J woodlands are common targets for fuel reduction treatments and restoration. If ecosystem responses following fuel reduction treatments can be predicted, then restoration may be achieved simultaneously. In this study, we examine the long-term impacts (10 years) of two common fuel reduction treatments: 1) mechanical mastication (“mastication”), and 2) hand thinning followed by piling and burning debris (“hand-pile”) at two persistent P-J woodlands in southeastern Utah, with and without seeding prior to treatment. We determine the success of restoration following treatments through quantifying the cover of desirable (native status) and non-desirable (introduced status that were not seeded) herbaceous understory. Our results indicate hand-pile paired with seeding achieves restoration goals (increase in desirable species cover) more effectively than mastication paired with seeding. Our assessment of seeding and no seeding in mastication plots indicate that regional weather variation following initial seed deposition has a greater effect on desirable species colonization than the act of seeding itself.

Date Awarded
  • 2022-11-1
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Last Modified
  • 2022-11-03
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