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Long-term impacts of fire and mass wasting on solar loading and stream heating in mountain streams of central Idaho

Author(s): C. W. Welcker, John M. Buffington, Bruce E. Rieman, Charles H. Luce, J. A. McKean
Year Published: 2005

The immediate impacts of watershed disturbances such as forest fires, debris flows, and hyperconcentrated flows to lotic systems can include the local decimation of fish, amphibian, and insect populations, but the long-term impacts to biota may have more to do with the trajectory of stream habitat recovery from disturbance. This highlights the importance of understanding the mechanisms of disturbance and the timing of recovery to evaluate the full implications of disturbance to streams. Our work in the Idaho Batholith focuses on stream temperature because the distribution of cold water habitat is a key determinant of the presence of salmonids and because previous work has shown that recently disturbed streams are significantly warmer than undisturbed streams. The present study builds upon this work by looking at the effects of fire and mass wasting separately and in combination, as compared to undisturbed reference streams. We also studied different ages of disturbance from recent (1995-2003) to older (1964). Solar radiation is expected to dominate the heat budgets of these stream reaches, so the key variables of solar loading, stream width and depth, shading (measured with hemispherical photo analysis), and estimated velocity, were compared to the reach-scale stream heating to understand the mechanisms of thermal disturbance and recovery. Preliminary results indicate that mass-wasting has a stronger impact on stream heating than fires, and that while streams return to pre-disturbance conditions after 40 years, there is little sign of recovery 10 years after fires or fires and mass wasting. These results can be used to assess the long term risks to salmonid habitat due to watershed disturbances.

Citation: Welcker, C.W.; Buffington, J.M.; Rieman, Bruce E.; Luce, Charles H.; McKean, J. 2005. Long-term impacts of fire and mass wasting on solar loading and stream heating in mountain streams of central Idaho, abstract. American Geophysical Union. Fall Meeting.
Topic(s): Fire Effects, Ecological - Second Order, Aquatic Life, Water
Ecosystem(s): Riparian woodland/shrubland
Document Type: Conference Proceedings
NRFSN number: 11433
FRAMES RCS number: 8235
Record updated: Feb 4, 2014