Date of Award:

5-1998

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Department name when degree awarded

Forest Resources

Committee Chair(s)

David W. Roberts

Committee

David W. Roberts

Committee

James N. Long

Committee

Dale L. Bartos

Abstract

The history of Populus tremuloides regeneration in the Intermountain West, particularly western Wyoming, is one of prolific vegetative reproduction following wildland fire. The reproductive physiology of aspen and its disturbance-response characteristics are explored through a review of previous studies. The combination of fire suppression and increased herbivory on aspen by wild and domestic ungulates is likely facilitating conifer invasion of areas historically dominated by aspen as has been observed in parts of Wyoming, Utah, and Colorado over the past 100 years. A case study of the regenerative response of aspen to wildland fire in western Wyoming demonstrates how physiology, life history characteristics, and disturbance regimes affect the presence and distribution of aspen across the western landscape.

The regenerative response of aspen, Populus tremuloides, was monitored following two spatially overlapping wildland fire events on Shadow Mountain that occurred 6 years apart. The fires left a landscape mosaic of unburned, once-burned, and twice-burned sites ranging in size from approximately 0.1 to 12.0 hectares. Aspen suckering response in burned areas was significantly greater than that observed in unburned areas. Less regeneration occurred on plots that reburned than on those that burned only once; however, by the second year post-fire sucker numbers on the reburned plots were not statistically significantly lower than they were on the plots that burned only once. Self-thinning of suckers observed on the plots burned only in the first fire suggests that sucker numbers on once-burned and twice-burned plots will converge over a 6- to 10-year period. Sucker numbers on burned plots appear sufficient for stand replacement, while those on unburned plots are very low, potentially consistent with seral aspen stands that may be subject to conifer encroachment.

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