Characterization of particulate organic matter transported by some Cascade mountain streams

Field and laboratory studies were conducted to characterize concentrations, factorsdetermining concentrations, particle size composition, and presumed food quality ofparticulate organic matter (POM) transported by streams of four different orders inOregon's Cascade Mountains. Devils Club Creek (first order) and Mack Creek (thirdorder) as high gradient, heavily shaded headwater streams receive large amounts of forestdebris. Lookout Creek (fifth order) and the McKenzie River (seventh order) have lowergradients and more organic inputs from in situ aquatic primary producers and organicmatter drifting from upstream areas than from the adjacent forest. Concentration of par-ticulate organic matter is low during periods of nonstorm discharge, and not significantlyrelated to stream power or type of organic input. All streams transport a mean POMparticle size 1 mm) to fine (0.45 pm-1 mm) organic matter (CPOM:FPOM) is near zero, butremains elevated for the McKenzie River during all seasons. As determined by the amountof chlorophyll, carbon to nitrogen (C:N) ratio, percentage of organic matter and respira-tion rate, the presumed food quality of drifting organic matter is potentially better in down-stream reaches.
Key words: food quality, detritus, organic matter, streams, rivers, watershed, drift, transport