Dissertation/Thesis Abstract

Effects of Recreation and Natural Disturbances on Invasive Exotic Plant Abundance in Rocky Mountain National Park
by Downing, Rosemary, M.S., University of Colorado at Denver, 2020, 110; 28086786
Abstract (Summary)

Invasive exotic plants can cause significant ecological changes that span large spatial and temporal scales. Invasive exotic plants have been increasing in number and extent in Rocky Mountain National Park and such proliferation is a primary resource management concern. Two of the most important factors regulating invasive exotic plant establishment and spread are resource availability and propagule pressure. Natural disturbances can cause changes to available resources which create opportunities for invasive exotic plant colonization and proliferation. Outdoor recreation can enhance propagule pressure by transporting and depositing invasive exotic plant seeds along trails. This study examines the effects of enhanced propagule pressure from recreation in areas affected by two important disturbances in the Rocky Mountain region, bark beetle outbreaks and fire. Native plant community, invasive exotic plant abundance, tree mortality, and disturbance agent were measured in 227 plots along thirteen trails in Rocky Mountain National Park. Linear models were used to determine the effects of vegetation type, bark beetle mortality, burning, and visitation on invasive exotic plant abundance. Overall, vegetation type was an important factor controlling IEP abundance (adjusted R2 = .7227, p < .0001) which modulated the effects of visitation and disturbance. Visitation (adjusted R2 = 0.6841, p < .0001) and tree mortality (adjusted R2 = 0.7926, p < .0001) from mountain pine beetle (Dendroctonus ponderosae) had significant effects on invasive exotic plant abundance in lodgepole pine stands. Linear models which include both explanatory factors were best fit to IEP abundance (Akaike weight = 1, adjusted R2 = .8645), indicating coregulation between these two invasion components. This study also shows that fire has severe and long-lasting effects on IEP abundance (Adjusted R2 = .7663, p < .0001). Lastly, this study examined which variables are most important for IEPs to proliferate beyond foothold populations which result from direct trail effects. Disturbance was found to create important pathways for IEPs to proliferate beyond the trail periphery and into backcountry areas (fire: adjusted R2 = .692, p < .0001; bark beetle: adjusted R2 = .5966, p < .0001). This study provides novel evidence that mortality from mountain pine beetle can support IEP establishment and spread. Additionally, findings are interpreted to demonstrate coregulation between resource availability and propagule pressure and important pathways for IEP spread. Finally, the findings of this study are considered through a management lens and placed within an invasion framework that acknowledges the interplay between vegetation type, propagule pressure, and resource availability. Incorporating these variables into a single, hierarchal framework provides direction for IEP prediction, monitoring, and management in backcountry areas of Rocky Mountain National Park.

Indexing (document details)
Advisor: Briles, Christy E.
Commitee: Kelsey, Kathy, Simon, Gregory
School: University of Colorado at Denver
Department: Environmental Sciences
School Location: United States -- Colorado
Source: MAI 82/4(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Ecology, Environmental science, Natural Resource Management
Keywords: Biological invasion, Disturbance, Invasive exotic plants, Recreation ecology
Publication Number: 28086786
ISBN: 9798684638411
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