Year of Award

2009

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Geography

Department or School/College

Department of Geography

Committee Chair

Anna Klene

Commitee Members

Eric Edlund, Sam Cushman, Susan Rinehart, Ulrich Kamp

Keywords

CCA, climate change, environmental gradients, GIS, gradient analysis, landscape trajectories, NMDS, ordination statistics, Paleobiogeography, pollen analysis, statistics, trajectory analysis, vegetation change

Abstract

The goal of this study was to quantitatively analyze and map the vegetation composition of forest, grassland, and steppe ecosystems in the northwestern United States in the present and through the last 9,000 years. The modern analysis used canonical correspondence analysis (CCA) on pollen percentages from recent sediment cores reflecting modern vegetation assemblages and climates to evaluate the amount of influence of selected environmental variables on present species distributions. The fossil analysis used non-metric multi-dimensional scaling (NMDS) on a merged database containing relative pollen percentages from the last 9000 years. A predefined list of environmental parameters and floristically and ecologically important pollen percentages were used to measure the dissimilarity between modern and fossil pollen regimes over the region at specific time periods. The numeric values obtained from both statistical analyses were interpolated and mapped via Geographic Information Systems (GIS) to display major vegetation types throughout the northwestern United States through time, allowing visual assessment of changing environmental gradients.

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© Copyright 2009 Christopher Caleb Stump