Change isn't always bad: trout in headwater streams show increased growth following wildfire.
Heck, Michael*,1, Gresswell, Robert2, 1 Oregon State University, Corvallis, OR2 USGS Northern Rocky Mountain Science Center, Bozeman, MT
ABSTRACT- Wildfire, a largely terrestrial perturbation, is broadly recognized as an agent of disturbance and ecological change in forested biomes. Effects of postfire conditions on biotic components of aquatic systems have been less well-documented, although hypothetically the two are strongly connected. In fact, the influence of wildfire may be most profound in headwater streams because of the tight linkage between aquatic and terrestrial ecosystems. By observing growth of a tertiary consumer (coastal cutthroat trout, Oncorhynchus clarkii clarkia), we sought to investigate how postfire conditions influence fish growth in headwater streams. During the summer of 2002, wildfire burned portions of three headwater catchments in western Oregon. Burn severities ranged from moderate to severe. An unburned catchment was selected as a control. For three years following the wildfire, all fish-bearing portions of the stream network in the four catchments were surveyed, and scale samples were collected for age and growth analysis. Despite considerable alterations in the physical stream environment following the wildfire, growth of coastal cutthroat trout appeared to be positively related to wildfire severity. It appears that increased solar radiation and water temperatures triggered a bottom-up ecosystem response resulting in greater growth of fish in the burned catchments. Contrary to the commonly held perception that wildfire is detrimental, these results suggest that over short time scales, the effects of wildfire on stream ecosystems may benefit some members of the aquatic community.
Key words: wildfire, growth, coastal cutthroat trout
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