PARENT SESSION
Poster Session #8: Riparian Ecology.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Dendroecological study of black cottonwood dynamics along regulated and unregulated rivers in British Columbia.

Mast, Joy¹, Stevens, Lawrence¹, ¹

ABSTRACT- Dendrochronological data can be modeled to develop a longer-term understanding of riparian tree responses over pre-impoundment and post-impoundment time. Flow regulation can strongly affect riparian tree growth and seedling establishment, as has been detected on the regulated Missouri, in the Grand Canyon, in southern Alberta, and in the Pacific Northwest. In this study, we used tree ring data to model black cottonwood (Populus trichocarpa) growth in relation to flow regimes on eight regulated and unregulated rivers in southern British Columbia. Black cottonwood cores were analyzed to determine both the magnitude and timing of tree growth responses to past flow regimes in both types of river systems. Overall, the trees sampled along the regulated rivers established as a cohort following a high flow event, with moderately fast growth and strong releases after subsequent high flow events. In contrast, the black cottonwoods along the unregulated rivers were slower growing, older, and more sensitive to suppression events. Such analysis enhances the understanding of the role of the timing and frequency of past flows and floods across a landscape, which are important determinants of riparian vegetation. Understanding patterns of change and the potential to alter future riparian tree growth requires a sound understanding of existing conditions and past growth patterns. Development of a descriptive model of tree growth under various flow regimes will provide managers with a means of evaluating the options for riparian management.

KEY WORDS: Populus trichocarpa, flow regime, dendroecology, British Columbia