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Stream succession: channel changes after wildfire disturbance

Author(s): Nicholas E. Schiedt
Year Published: 2005

One concept in geomorphology is that vegetation is a fundamental control on sediment and water supplies to streams and, therefore, on downstream fluvial processes and channel morphology. Within this paradigm, wildfire has been implicated as a major driving force behind landscape erosion and changes to stream channels, periodically yielding pulses of sediment from uplands that may drive changes to stream channels. However, channel response to wildfire has not been well studied over long periods (>10 years), and the occurrence and nature of long-term changes in channel characteristics remain to be documented. The long-term effects of wildfire disturbance on channel characteristics were examined in moderate-gradient (2-4% slope), unconfined, mountain streams in the Idaho batholith. The study was designed using a space-for-time substitution, and three different times since wildfire were considered: recent (15-20 yrs.), mid (80-110 yrs.), and old (>150 yrs.). Characteristics of interest included measures of channel morphology (e.g., channel geometry, pool spacing, residual depth, substrate size) and wood (e.g., amount, location, function, size). Multi-response permutation procedures were used to measure between treatment variability. Results show that none of the 17 morphologic characteristics varied between treatments, and only 3 out of 25 wood characteristics varied between treatments (proportionality = 0.10). The lack of morphologic variability between treatments implies that wildfire disturbance does not have a long-term effect on channels of this stream type, suggesting that moderate-gradient, unconfined channels may act as relatively stable, potentially productive, refugia for aquatic organisms in areas prone to wildfire.

Citation: Scheidt, Nicholas E. 2005. Stream succession: channel changes after wildfire disturbance. Moscow, ID: University of Idaho. 60 p. Thesis.
Topic(s): Fire Effects, Ecological - Second Order, Water, Fire History
Ecosystem(s): Riparian woodland/shrubland
Document Type: Dissertation or Thesis
NRFSN number: 11414
FRAMES RCS number: 6514
Record updated: Apr 1, 2015