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Date Permissions Signed

8-8-2020

Date of Award

Summer 2020

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Studies

Degree Name

Master of Arts (MA)

Department

Environmental Studies

First Advisor

Flower, Aquila

Second Advisor

Bach, Andrew J.

Third Advisor

Medler, Michael J.

Abstract

The subalpine ecotone is experiencing significant change in habitat availability and connectivity as a result of climate change and climate variability. To understand how these changes vary temporally and spatially in the Pacific Northwest, we collected cross-sections and counted whorls of conifers along four transects around Mt. Baker, Washington in the North Cascades. In addition to the samples collected, we also gathered data on microsite conditions that impact seedling establishment. Using partial correlation analyses, we compared establishment dates to climate variables in five-year bins, and used normal correlation analyses along with other statistical tests to determine the effect of various microsite variables on establishment. Our results show that establishment has occurred in pulses throughout the 20th century, with greater establishment on drier sites during periods of greater precipitation, and greater establishment on wetter sites during periods of higher temperatures. We found that April precipitation and September temperature are particularly strongly correlated with establishment rates, suggesting that the best conditions for conifer seedling establishment occur in years with the warmth and soil moisture needed for the growing season to last longer into late summer. Within individual meadows, conifer seedling establishment was greater on convex surfaces and in areas with a higher percentage of vaccinium cover. The tree species present in each meadow also play a role in determine the timing of establishment pulses, and the distribution of encroaching seedlings, with silver fir only being able to establish close to its seed source and yellow cedar establishing on drier microsites. Our findings at Mt. Baker show that periods of conifer establishment have occurred somewhat synchronously across multiple mountains in the region, but we also identified distinct spatial and temporal differences linked to local site conditions.

Type

Text

Keywords

Biogeography, Landscape ecology, Subalpine ecotone, Mountain environments, Conifer encroachment, Dendrochronology, Mount Baker, Washington Cascades, Pacific Northwest

Publisher

Western Washington University

OCLC Number

1190720596

Subject – LCSH

Biogeography--Climatic factors--Washington (State)--Baker, Mount; Conifers--Washington (State)--Baker, Mount--Growth; Mountain meadows--Washington (State)--Baker, Mount; Dendrochronology--Washington (State)--Baker, Mount

Geographic Coverage

Baker, Mount (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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