Year of Award
2025
Document Type
Thesis
Degree Type
Master of Science (MS)
Degree Name
Systems Ecology
Department or School/College
Ecosystem and Conservation Sciences
Committee Chair
Diana L. Six
Commitee Members
David Affleck, Philip E. Higuera
Keywords
Whitebark pine, Idaho, mountain pine beetle, climate change
Subject Categories
Other Ecology and Evolutionary Biology
Abstract
Recent climate-driven outbreaks of mountain pine beetles (Dendroctonus ponderosae) in whitebark pine (Pinus albicaulis) have raised fears of increasing whitebark pine mortality with increased warming and drought due to climate change. However, little is known about how whitebark pine responds to climate, what characteristics may predict whitebark pine susceptibility to mountain pine beetle outbreaks, or how these may interact. This information is critical in understanding how whitebark pine might persist in a changing climate. My research investigated how whitebark pine growth responds to various climate variables and how these responses may be predictive of attack by mountain pine beetle. I studied growth-climate interactions in whitebark pine at three arid and two mesic sites in Idaho. There were recent beetle outbreaks at the arid sites, but not at the mesic sites. I also researched if whitebark pine is more energy- or water-limited and whether warming over the last decades has resulted in a shift from one limitation type to the other. I found that growth rate was predictive of beetle host-tree selection at the stand level, but not at larger scales. At two sites, trees that were eventually killed by mountain pine beetle grew faster than survivors prior to 1940 but then grew slower than survivors from 1940 up to the beetle outbreak in the early 2000s. At the third arid site, beetle-killed trees grew faster than survivors until 2000, then growth rates converged in the early 2000s prior to the beetle outbreak. I also found significant differences in growth rates between older and younger trees at the study sites. I found that some groups and cohorts (survivor, beetle-killed, older, younger) experienced a release from energy-limitation around 1940, but that there were also shifts from energy- to water-limitation for a subset of trees at the mesic sites. The results from my study are encouraging as they show whitebark pine responds to climate in a variety of ways that indicates high genetic diversity within and among populations. These findings should serve as a cautionary tale for managers on the importance of considering local adaptation and maintaining extant genetic diversity.
Recommended Citation
Alverson, Hannah Rose, "MOUNTAIN PINE BEETLE HOST TREE SELECTION AND CLIMATE-GROWTH DYNAMICS IN WHITEBARK PINE" (2025). Graduate Student Theses, Dissertations, & Professional Papers. 12437.
https://scholarworks.umt.edu/etd/12437
© Copyright 2025 Hannah Rose Alverson
