Describing the Alpine-Treeline Ecotone on Mount Arrowsmith and its response to climate change over 20 years
Date
2026
Authors
Grogan, Erin
Journal Title
Journal ISSN
Volume Title
Publisher
University of Victoria
Abstract
The Alpine-Treeline Ecotone (ATE) is a temperature-sensitive transitional plant community, which has had various responses to climate change across the world. On Vancouver Island, it is predicted that the extent of alpine-tundra plant communities will be reduced and replaced with mountain hemlock forests as warming increases the ranges of lower elevation species. This study aims to describe the plant community composition within the ATE at Mount Arrowsmith, on Vancouver Island, and investigate directional changes in community composition over the last 20 years, using the GLORIA protocol. At Mt. Arrowsmith, the ATE is dominated by rock cover with low vascular plant cover and most closely resembles Rhizocarpon geographicum plant communities found elsewhere in the southern Coast Mountains. Microsites result in two vegetation associations being present: Penstemon – Juniperus on xeric sites and Phyllodoce – Abies on more developed soils. No significant changes in plant community composition over the last 20 years were detected, with vascular plant cover remaining stable and rock remaining the dominant cover. Species richness also remained stable over the study period; however, turnover occurred with species gained and lost with each survey and one new invasive species in 2025. The plant community within the ATE at Mt. Arrowsmith has not exhibited directional change over the last 20 years. Continued monitoring will be needed to assess plant community responses to ongoing climate change.
Supervisor: Dr. Terri Lacourse
Co:Supervisor: Dr. Noémie Boulanger-Lapointe