Item: Snow avalanche path ecology: examples from the san juan mountains, colorado
Title: Snow avalanche path ecology: examples from the san juan mountains, colorado
Proceedings: Proceedings Whistler 2008 International Snow Science Workshop September 21-27, 2008
Authors: Sara Simonson, Thomas Stohlgren, Chris Landry, Steven Fassnacht.
Abstract: We evaluated landscape ecology approaches to characterize snow avalanche paths based on patterns of plant species composition and evidence of disturbance. Historical records of avalanche incidents, patterns in the annual growth layers of woody plants, and distributions of plant species can be used to quantify and map the frequency and magnitude of snow slide events. Near Silverton, Colorado, a series of snow storms in January of 2005 resulted in many avalanche paths running full track at 30 and 100 year return frequency. Many avalanches cut fresh trimlines, widening their tracks by uprooting, stripping, and breaking mature trees. Powerful avalanches deposited massive piles of snow, rocks, and woody debris in their runout zones. We used cross-section discs and cores of representative downed trees to detect dendro-ecological signals of past snow avalanche disturbance. Avalanche signals included impact scars from the moving snow and associated wind blast, relative width of annual growth rings, and development of reaction wood in response to tilting. Initial measurements of plant diversity and disturbance along the elevation gradient of an avalanche path near Silverton indicate that avalanche activity influences patterns of forest cover, contributes to the high local plant species diversity, and provides opportunities for new seedling establishment.
Presenters: Sara Simonson.
Keywords: snow avalanche path vegetation, plant species diversity, tree-ring analyses, disturbance ecology