Lamberti, Gary A.; Gregory, Stan V.; Ashkenas, Linda R.; Wildman, Randall C.; Steinman, Alan D. 1989. Influence of channel geomorphology on retention of dissolved and particulate matter in a Cascade Mountain stream. In: Abell, Dana L., tech. coord. Proceedings of the California Riparian Systems conference: protection, management, and restoration for the 1990s; 1988 September 22-24; Davis, CA. Gen. Tech. Rep. PSW-110. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station: 33-39.
Retention of particulate and dissolved nutri-ents in streams is a major determinant of food avail-ability to stream biota. Retention of particulate matter(leaves) and dissolved nutrients (nitrogen) was studiedexperimentally during summer 1987 in four 300-500 mreaches of Lookout Creek, a fifth-order stream in theCascade Mountains of Oregon. Constrained (narrow val-ley floor) and unconstrained (broad valley floor) reacheswere selected within old-growth and second-growth ri-parian zones. Gingko leaves and ammonium were re-leased into the channel and retention rates were mea-sured. Retention of leaves and nutrients was 2-4 timeshigher in unconstrained reaches than in constrainedreaches, in both old-growth and second-growth riparianzones. Retention was enhanced by increased geomor-phic complexity of channels, diversity of riparian vege-tation, presence of woody debris, and heterogeneity instream hydraulics, sediments, and lateral habitats. Un-constrained reaches express these qualities and thus arecritical areas for retention of particulate and dissolvednutrients in stream ecosystems.