| |
Communication at the NABS Annual meeting, Keystone, 2000
(139) LONG-TERM DYNAMICS OF LARGE WOOD IN A THIRD ORDER MOUNTAIN STREAM OF THE WESTERN CASCADES, OREGON.
L.R. Ashkenas, S.V. Gregory, R.C. Wildman, and M.A. Meleason. Dept. of Fisheries & Wildlife, Oregon State University, Corvallis, Oregon 97331
Since 1985, we have been studying large wood in 750 m of 400 year old-growth forest and 300 m of 30 year clearcut in Mack Creek, Oregon. Within this 1.1 km section of stream, all pieces of large wood >1 m long, >10 cm diameter) are tagged and inventoried annually. Data collected include dimension, location, geomorphic position, and decay. Densities of large wood in the old-growth reach are 0.24 pieces/m2, with volumes of 0.08 m3/m2. Densities and volumes in the clear-cut were significantly lower. Most of the wood was found in accumulations of three or more pieces; in the old-growth 29% were in channel-spanning jams. The long-term nature of the study has allowed us to measure rates of input, fragmentation and movement. Recruitment of wood to both channel and floodplain was highly variable, and more closely related to climatic events (windstorms, snowfall) than to discharge events. Rates of in-channel movement were generally low (<1%) in any given year, but during a 35-year flood (1996) 11% of the logs in the old-growth and 25% of those in the clearcut moved >10m. The interaction between channel geomorphology, hydrology and wood dimension determines overall dynamics of large wood in riverine ecosystems.
Presented at 2:30 PM on Tuesday, May 30, 2000 in Flood Disturbance
|
|
