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Publication Title: Disturbance of aquatic and riparian systems in a mountain river network [Abstract]
Year: 2001 Publication Type: Abstract
H. J. Andrews Publication Number: 2949
Citation: Swanson, Frederick J.; Johnson, Sherri L.; Snyder, Kai U.; Acker, Steven A. 2001. Disturbance of aquatic and riparian systems in a mountain river network [Abstract]. In: Proceedings, 16th annual symposium of the International Association of Landscape Ecology--U.S. chapter: pattern, process, scale, and hierarchy: interactions in human-dominated and natural landscapes; 2001 April 25-29; Tempe, AZ. [Place of publication unknown]: International Association of Landscape Ecology: 204.
Online PDF: http://andrewsforest.oregonstate.edu/pubs/pdf/pub2949.pdf
Abstract: Patterns of disturbance in aquatic and riparian systems in mountain landscapes can be strongly influenced by the structure of stream networks. Network structure determines, in part, the distribution of geomorphic processes and their effectiveness as disturbance agents within stream systems. A 50-year record of debris flows in a Cascade Mountain landscape reveals a concentration of events in a limited set of the first-through third-order channels and a shifting mosaic of linear disturbance patches within the stream and riparian network across that part of the landscape. Channel segments not subjected to recent debris flows may serve as refuges in debris-flow producing floods, and sources of organisms to recolonize severely disturbed patches. Study of a major flood in 1996 on fourth- and fifth-order channels suggests that the widespread, 30-year-old, riparian alderstands experienced highest severity disturbance (removal) where floated wood was moving in a congested manner. These batches of wood were commonly delivered to the larger channel by debris flows from tributaries. Uncongested wood movement (floating individual pieces) tended to topple trees without removing them. Analysis of stem-map data from before and after the flood in a wide valley floor area with extensive alder stands shows a fine-grained pattern of disturbance patches of toppled and removed stems. These patterns reflect changes in channel position, impacts of floated wood, and other processes influenced by channel position. Aquatic habitat was altered directly by channel change and bed turnover, as well as indirectly by alteration of the riparian zone and its influences on the aquatic system. These observations form a basis for defining both deterministic and more stochastic properties of the disturbance regime over this mountain stream network.
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