Undergraduate Honors Theses

Thesis Defended

Spring 2013

Document Type

Thesis

Department

Ecology and Evolutionary Biology

First Advisor

Carol Wessman

Abstract

Mortality caused by mountain pine beetle and spruce beetle have together affected vast areas of forest in Northwestern Colorado throughout the last 15 years. In the midst of such a widespread bark beetle epidemic, it is crucial that land management agencies such as the USDA Forest Service understand how different forest types are responding to these natural disturbance events that have historically played an ecologically important role, in order to foster the future resilience of these forests. Particularly, it is practical and important to develop an understanding of how the bark beetle disturbances are interacting with management strategies such as timber harvest. The purpose of the present study was to investigate the influences of multiple disturbances on soil physical and chemical properties, as well as the successional trajectory of a mixed subalpine forest. Thirty plots were established with 10 in each of three treatments, consisting of forests of bark beetle induced mortality (beetle kill), logged beetle kill forests, and intact/green (control) forests. In each plot, soil samples were collected and number/species of seedlings, fractional cover of forest understory, coarse woody debris, and canopy trees were measured and recorded. While forest conditions do not differ substantially between forests subject to beetle kill and intact/green forests, in many instances, harvesting of beetle kill stands is altering soil properties and forest understory conditions such that the dominance of subalpine fir establishment/accelerated growth associated with forests of high beetle mortality is suppressed, and no alternative successional trajectory is favored as of now.

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