Changes in a reach of a northern California stream following wildfire |
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Authors: | Kenneth B Roby David L Azuma |
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Institution: | (1) Pacific Southwest Research Station, 94701-0245 Albany, California, USA |
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Abstract: | One reach of a northern California stream, burned by intense wildfire in 1979, was studied to monitor changes and recovery
from the fire. Benthic macroinvertebrates collected three weeks and one to four, six, eight, and 11 years following the wildfire
were used to assess stream condition and compared to samples from a reach of a nearby unburned stream. Transportable sediment
was measured 11 years following the fire. The fire was also used as a worst case example to compare results with a standard
cumulative watershed effects assessment methodology.
Benthic invertebrate density and taxa richness of the burned reach were both low compared to the unburned reach three weeks
after the fire. Mean density was significantly higher in the burned reach in the three years following the fire, while taxa
richness was significantly lower in the burned reach over the same time period. Higher density and lower richness in the burned
reaches persisted throughout the study period but were not significant after three years. Mean Shannon diversity of the burned
reach was significantly lower than that of the unburned reach for each year of the study, although absolute differences diminished
throughout the 11-year study period.
Transportable sediment was significantly higher in the burned reach than the unburned comparison. Pearson correlations between
sediment and biological metrics were weak. Although the correlation between invertebrate diversity and a measure of watershed
disturbance (equivalent roaded acres) was high (r=0.95) for the burned watershed, the measure appeared to be a poor indicator of cumulative effects on stream condition. The
measure (ERA) was poorly correlated with invertebrate diversity in the unburned reach and, while the ERA calculations indicated
substantial recovery, biological and physical measures indicated recovery of the burned stream reach was incomplete. |
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Keywords: | Stream Wildfire Macroinvertebrates Diversity |
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