Conifer Invasion: A Multivariate Analysis of Seedling Establishment and Encroachment around Mt. Baker, WA

Authors: Benjamin Hagedorn*, Western Washington University, Aquila Flower, Western Washington University
Topics: Biogeography, Mountain Environments, Physical Geography
Keywords: Dendrochronology, Subalpine Ecotone, Mountain, Forests
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

Conifers are invading many subalpine meadow areas and converting the meadows to subalpine forest. Subalpine meadows are critical habitat for numerous species and serve an important role in the hydrologic cycle. The conversion to a more forested landscape is fragmenting meadow habitat and reducing their ecosystem services. Mt. Baker is further north than existing Cascade sites and it is unknown whether similar patterns and processes occur here. In the summer of 2018, we led groups of volunteers to collect cross-section disks from 90 mountain hemlock, 27 Pacific silver fir and 18 Alaska yellow cedar along four transects at Mt. Baker. Our preliminary analysis of the data indicates a relationship between encroachment density and the microtopography of the meadows we sampled, with more dense encroachment occurring on convex surfaces. Differing relationships exist between encroachment density and types of vegetation cover, and there is no relationship between distance from seed source and encroachment density of mountain hemlock or yellow cedar. However, silver fir does tend to establish closer to a seed source. We intend to determine the significance of these spatial patterns as well as the relationship between climate variables and temporal establishment patterns. Our research goal is to understand the complex interplay of spatial and temporal variables on conifer encroachment, and to see how the patterns observed at Mt. Baker compare to the patterns observed throughout the region. A detailed understanding of these patterns will help determine the variability of climate change impacts at the subalpine ecotone in the Washington Cascade

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