| Summary: | The temperatures of stream water and the stream bed influence biogeochemical processes and the
growth and distribution of fish and macro-invertebrate species in streams. While numerous
studies have examined the effects of various harvesting practices on stream temperature, none has
estimated the effects on bed temperature, or conducted heat budget analysis before and after
harvest to assess the mechanisms that control the magnitude of post-harvest stream heating.
In this study, we analyzed data from a paired-catchment experiment involving both
control and treatment streams and pre- and post-harvest monitoring. The partial retention
harvesting resulted in removal of 50% of the basal area along 300 m of the channel in the
treatment catchment. Stream temperature, bed temperature, riparian microclimate and stream
hydrology were monitored in the treatment stream both before and after harvest. Daily maximum
stream temperatures increased by up to over 7 °C during summer. Effects on winter temperatures
were relatively small. Summer bed temperatures increased by as much as 6 °C, with greatest
warming in areas of down-welling flow into the stream bed. Heat budgets were estimated for two
reaches of a headwater stream before and after partial retention harvesting. Heat budget
components responded in variable ways to the logging treatment depending on the reach, date,
and weather. Incoming solar radiation was the largest input of energy into the stream following
harvesting, while latent heat, hyporheic heat, groundwater heat, and bed heat exchanges tended to
reduce the amount of daytime stream heating after harvest. These results will assist in
understanding and predicting the spatial and temporal variability in stream temperature response
to forest harvesting. === Arts, Faculty of === Geography, Department of === Graduate
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