Gregory, S. V.. Oregon State University, Stanley.Gregory@orst.edu
, . V.. ,
ANALYSIS OF ECOLOGICAL PATTERNS AND HISTORICAL CHANGE IN MANAGEMENT AND RESTORATION OF LARGE RIVERS
Large rivers present complex challenges for management and restoration. Historical changes in physical and biological processes of river ecosystems are difficult to reconstruct, and large spatial scales limit sampling and integration. Recent concepts such as the River Continuum, Flood Pulse, and Seral Discontinuity provide important ecological frameworks for large rivers. We present an analysis of historical changes in 290 km of the mainstem Willamette River, which flows through a 30,000 km2 basin in Oregon. Based on river surveys from 1850 to 1995, we determined amount of channel change and associated changes in floodplain forests. In upstream reaches with anastomosed channels, more than 50% of secondary channels and islands have been eliminated. In downstream sections with simple meandering channels, secondary channel change has been slight but area in islands has decreased. Floodplain forest originally occupied 85% of the river margin, but now are reduced to less than 15%. Tributary junctions and multiple channel reaches now represent areas of high diversity. Fish species richness in these complex reaches is 25% higher than straight reaches. Complex reaches also are more geomorphically dynamic. We have identified restoration goals based on a framework for screening processes for physical disturbance history, ecological potential, and socioeconomic opportunities and constraints.
Day: Monday, Feb. 1
Time: 02:00 - 02:30pm
Location: Hilton of Santa Fe