Year of Award

2018

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Forestry

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Edwin Burke

Commitee Members

David L.R. Affleck, Ray Callaway

Keywords

whitebark pine, Rocky Mountains, Pinus albicaulis, dendrochronology

Subject Categories

Forest Sciences

Abstract

Along with fluctuating precipitation and temperatures in the form of climate change, whitebark pine (Pinus albicaulis) has seen a territory wide increase in mortality leading to a decline in population. While the most direct influences on whitebark pine health and mortality are mountain pine beetle (Dendroctonus ponderosae) outbreaks, fire exclusion policies, and the spread of white pine blister rust (Cronartium ribicola), climate change can impact the intervals and severity of such beetle, rust, and fire disturbances, and may affect the growth and health of whitebark pine directly. The objectives of this study were to identify whitebark pine stands within the northern US Rocky Mountains exhibiting low or no impacts of beetle attack and blister rust, to document the regeneration levels and structural components of these stands, and to examine the climatic controls on radial growth of the mature whitebark pine over the last 100 years. Across the high elevation forests of Montana, Idaho, and Wyoming, 92 minimally disturbed stands were identified. While free of blister rust and pine beetle damage, these stands still contained a high proportion of standing dead trees (24% of standing mature trees (>4.5” DBH) were dead on average). These stands also contained a high proportion of subalpine fir (on average, 14.4% of the mature tree density), but nonetheless exhibited high levels of whitebark pine regeneration (on average 1,195/acre below 4.5” DBH and 1,044/acre <4.5’ in height). Tree ring growth analyses of the mature whitebark pine did not show any long-term trends, but inter-annual variations were positively correlated with growing season precipitation and negatively correlated with growing season temperatures. Tree ring indices also show that more recent radial growth rates are still within the range of variability for the 100 years sampled and do not appear to be decreasing with the increasing stress predicted by ongoing climate change. Over the same 100 years, yearly mean climate averages calculated using PRISM data attributed to the individual sites showed a range of 30.7° F for maximum temperatures, 40.2° F for minimum temperatures, and 97.03” for total precipitation.

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© Copyright 2018 Sarah Flanary