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Geomorphic Controls of Spatial Pattern and Process at Alpine Treeline

Authors


  • *Funding for this research was provided by the AAG Geomorphology Specialty Group, the Hodges-Padilla Dissertation Research Scholarship, and the Ray and Marian Butler Scholarship in Environmental Geography, from Texas State University to the author. The National Park Service provided additional support through a GIP grant to the author. A large portion of this work was conducted with the U.S. Geological Survey through cooperative agreement #99CRAG0032 with David R. Butler. I sincerely appreciate the help of Dan Fagre from the U.S. Geological Survey for coordinating my research. Dianna Gielstra, Lynn Smollin, Evan Hammer, Dave Selkowitz, Paul Resler, Adam Krutchinsky, and George Malanson made important contributions in the field. I thank Michael McGahee for his assistance with the final manuscript, and four anonymous reviewers and Fred Shelley for their helpful comments on previous drafts of this manuscript. Finally, I thank my advisor, David Butler, and committee members George Malanson, Mark Fonstad, Deborah Bryan, and Richard Dixon for their helpful insights into this project.

Abstract

This study examines the role of surface geomorphic features in tree establishment at the alpine treeline in Glacier National Park, Montana, through the presentation of a multiscale, conceptual model of biogeomorphic relationships at alpine treeline. Empirical observations gathered through a multiscale field methodology over three summers serve as a base for the model. The model highlights the importance of surface geomorphic features, specifically boulders and terrace risers, in creating favorable local site conditions, largely by protecting seedlings from wind. The sheltering effect of surface features enables initial seedling establishment, and in some cases survival, above current treeline locations, thereby initiating a positive feedback effect that encourages subsequent tree establishment. Geomorphic features are therefore important in linking scales of pattern and process at the alpine treeline ecotone.

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