Controls on high elevation treelines in the Canadian Rocky Mountains

Authors: Ze'ev Gedalof*, University of Guelph, Emma Davis, University of Guelph, Robert Brown, University of Guelph, Heather Hager, University of Guelph
Topics: Biogeography, Mountain Environments, Climatology and Meteorology
Keywords: dendroecology, mountains, climate change, treeline ecotones
Session Type: Paper
Day: 4/6/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Marshall East, Marriott, Mezzanine Level
Presentation File: No File Uploaded


The distributions of many subalpine tree species have shifted as a result of recent climate change; however, there has been substantial variability in the movement of alpine treelines at local- to regional-scales. Here we report on a mixed-methods approach to understanding how and why some treelines are responding to climatic warming while others are not. Dendroecological reconstructions were used to document the rates and mechanisms of treeline advance at nine sites in the Canadian Rocky Mountains. At a subset of these sites seed addition and hervbivore exclosures were installed. Soils were also collected for a common garden experiment. Our results show that treeline advance is episodic, and occurs mainly through the establishment of “outpost” trees followed by infilling. Soil legacy effects appear to also be an important limit to seedling establishment, both in the field and in the greenhouse. Climatic effects include both temperature and precipitation, with apparently opposite effects on seedling establishment versus radial growth of mature trees. Conditions that inhibit the growth of mature trees are often associated with higher germination rates of seedlings. Surprisingly, seed predation by animals was relatively unimportant.

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