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Monday, April 9 • 11:30am - 11:45am
SYMPOSIA-05: A Comparative Analysis of Structural Characteristics in Old-Growth Coastal Temperate Floodplain Forests

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AUTHORS: Amanda Girard*, Simon Fraser University, School of Resource and Environmental Management; Sari Saunders, BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development; Paul Alaback, University of Montana; Ken Lertzman, Simon Fraser University, School of Resource and Environmental Management; Brian Buma, University of Alaska; Heather Klassen, BC Ministry of Forests, Lands, and Natural Resource Operations

ABSTRACT: Old-growth riparian forests are structurally complex and some of the most diverse ecosystems in the North Pacific Coastal Temperate Rainforest (NPCTR); however, regional variation in the structure and composition of these ecosystems is poorly understood. Having a strong understanding of this variability and its drivers is critical for refining landscape-level theory and models of old-growth development to inform conservation of riparian forests. We examined tree, snag, and coarse woody debris data from permanent, stand-mapped, Sitka spruce (Picea sitchensis) floodplain sample plots across 11° of latitude, from Southeast Alaska, along the British Columbia Coast, to Washington State. A combination of univariate, graphical, and multivariate analyses were used to assess variability in characteristics among these plots and against previously published data, and to evaluate the relative roles of climate, disturbance regime, biophysical site features, and their interactions in driving riparian structure. Two principal components explained 74% of variation in stand characteristics. The first component was associated with mean tree diameter at breast height (DBH), standard deviation (SD) of tree DBH, and number of large stems/ha (>100cm). The second component was strongly correlated with Sitka spruce density and total number of medium stems/ha (50cm 7.5cm (mean = 280 ± 161 SD), was higher in northern latitudes, and there were greater numbers of large trees in the south (mean = 25.98 ± 16.99 SD). Sub-regional climate was the primary driver of differences in plot characteristics, separating perhumid and seasonal rainforest riparian ecosystems. Levels of structural variation were consistent with our review of previous work on Sitka spruce floodplain forests in the NPCTR, suggesting consistent approaches to management and conservation of riparian systems may be effective across this latitudinal extent.

Monday April 9, 2018 11:30am - 11:45am CDT
Water Tower Parlor