REVELATIONS FROM A MILAN PROJECT: MEASURED CHANNEL WOOD PRODUCTION RATES IN SMALL, STEEP STREAM CHANNELS, COLUMBIA RIVER BASIN, USA

Long term ecological monitoring (now at year eight of three hundred, far shy of three centuries for building the Milan Cathedral), is underway to describe the functional roles of wood in small, steep stream channels, and to document the relationship between channel corridor vegetation, tree fall, channel wood, and sediment storage. Results from repeat measurements of 5800 trees, 2500 pieces of channel wood, and 300 sediment wedges are presented for three ecological processes: 1) rates of tree fall, and production rates of fallen trees making 2) fluvial (channel) wood or 3) terrestrial wood. After eight years of monitoring (2000-2008) at eighteen sites, one-third of fallen trees became fluvial (channel) wood, and two-thirds of fallen trees became terrestrial (down) wood. Over a third of fluvial wood was hydraulically active (within the channel bankful perimeter). The tree fall rate is about 0.6% per year. Most channel wood was above and near the channel, and not hydraulically active channel wood. The conversion rate (over 8 years) of fluvial wood into hydraulically and habi-tactically active forms (zones 1 and 2) is about 0.048% per year (<<1%/yr). Of the trees creating fluvial wood in channel zones 1 and 2 (within the wetted perimeter of the channel), over three-quarters fell in a band 0-15m away from the channel edge, and the rest fell in a band 15-23m away from the channel edge. The implications of terrestrial wood inputs, wood storage, fluvial import and export, and quantification of the ‘multiplier effect’, are discussed for wood budgets, forecasts, designs, and modeling.