Title page for ETD etd-05072012-142254


Type of Document Master's Thesis
Author Slyder, Jacob Brake
Author's Email Address slyder@vt.edu
URN etd-05072012-142254
Title Population Structure and Biophysical Density Correlates of Whitebark Pine (Pinus albicaulis) at Two Treelines in the Northern Rocky Mountains
Degree Master of Science
Department Geography
Advisory Committee
Advisor Name Title
Resler, Lynn M. Committee Chair
Kennedy, Lisa M. Committee Member
Thomas, Valerie A. Committee Member
Keywords
  • regeneration
  • alpine treeline ecotone
  • Pinus albicaulis
  • white pine blister rust
  • population structure
Date of Defense 2012-04-27
Availability restricted
Abstract
This study analyzes the structure and biophysical correlates of density of two whitebark pine

(Pinus albicaulis) populations in the northern Rocky Mountains. Whitebark pine is a keystone

species and an important component of treeline ecosystem dynamics; however, subalpine populations

have declined nearly rangewide in recent decades. Though declines in subalpine forests have been

well documented in the literature, few studies have assessed population structure and habitat

requirements at treeline. Various disturbances have combined to impact whitebark pine populations

across its range, but the primary threat at treeline sites in the northern Rocky Mountains is white pine

blister rust, caused by the exotic fungal pathogen Cronartium ribicola. In this study, I aim to: 1)

assess population structure and regeneration within two geographically different treelines

experiencing contrasting levels of infection, and 2) examine associations among several biophysical

variables and whitebark pine density to better understand treeline habitat variability and regeneration

patterns. I used density-diameter curves and non-parametric Kruskal-Wallis tests to compare

population structure between sites, and developed generalized linear mixed models to assess

correlations between whitebark pine density and biophysical site variables. The results demonstrate

that despite very different ecosystems and blister rust infection rates, our two study sites have similar

population structure. Our model results highlight marked differences between populations in terms

of biophysical correlates of density. While correlations are similar within site, seedlings and saplings

have stronger correlations with biophysical variables than established trees.

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