Divergent patterns of abundance and age-class structure of headwater stream tadpoles in burned and unburned watersheds

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Wildfire is a potential threat to many species with narrow environmental tolerances like the Rocky Mountain tailed frog (Ascaphus montanus Mittleman and Myers, 1949), which inhabits a region where the frequency and intensity of wildfires are expected to increase. The authors compared pre- and post-fire counts of tadpoles in eight streams in northwestern Montana to determine the effects of wildfire on A. montanus. All streams were initially sampled in 2001, two years before four of them burned in a large wildfire, and were resampled during the two years following the fire. Counts of tadpoles were similar in the two groups of streams before the fire. After the fire, tadpoles were almost twice as abundant in unburned streams than in burned streams. The fire seemed to have the greatest negative effect on abundance of age-1 tadpoles and was reflected in the greater variation in same-stream age-class structure compared with those in unburned streams. Despite the apparent effect on tadpoles, the authors do not expect the wildfire to be an extirpation threat to populations in the streams that they sampled. Studies spanning a chronosequence of fires, as well as in other areas, are needed to assess the effects of fires on streams with A. montanus and to determine the severity and persistence of these effects.

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ELECTRONIC FILE - Zoology