Year of Award

2019

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Forest and Conservation Science

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Andrew J. Larson

Commitee Members

Jon Graham, Kelsey Jencso, Cara Nelson, Carl Seielstad

Keywords

competition, Forest structural complexity, gap dynamics, snow dynamics, spatial patterns

Abstract

Ecological pattern-process linkages have been called the Rosetta’s stone of ecology. The pattern-process linkage is a feedback whereby ecosystem processes drive structural patterns, and vegetation patterns also strongly influence vital ecosystem processes. The role of competition and gap dynamics in creating spatial heterogeneity was assessed in Sitka-spruce western hemlock forests. Results indicated that despite low species richness, these forests are structurally diverse with the spatial imprint of competition obscured by gap dynamics through stand development. The influence of forest structural and spatial heterogeneity on snow accumulation and persistence was examined in a mixed-conifer forest. Tree neighborhood type (open, clump, individual) and winter leaf habit (deciduousness) had a significant effect on snow processes, likely driven by interception and the spatial variation of longwave radiation. Random forest models relied on forest canopy metrics associated with the amount, location, and type of forest vegetation to predicting peak snow water equivalent (SWE) and snow disappearance. Variation of peak snow density was not explained with canopy or terrain metrics. Models parameterized with ground and LiDAR based canopy metrics performed equally well for SWE and snow disappearance. The results of this research provide managers with new tools for objectively quantifying forest heterogeneity, informing treatments that seek to create structural and spatial complexity, and a method for estimating the distribution of snow accumulation and melt in complex forests. These studies provide a clear links between forest spatial patterns and important ecosystem processes including competition, gap dynamics, and snow accumulation and disappearance.

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© Copyright 2019 Eryn Elizabeth Schneider