The role of fine sediment in phosphorus dynamics and stream productivity in Rocky Mountain headwater streams: Possible long-term effects of extensive logging

Headwater streams in Alberta's Rocky Mountains are important in regulating aquatic ecosystem function and a range of downstream water resources but are vulnerable to stresses imposed by disturbances including those exerted by logging. The objectives of this research were to determine if the legacy of past forest harvesting impacts could be detected in altered sediment-nutrient dynamics and primary productivity in headwaters in the Rocky Mountains of southwestern Alberta. A descriptive, process-based case study was conducted in an undisturbed-disturbed watershed pair where one watershed had undergone extensive harvesting ending in 1990. The disturbed watershed was found to have higher concentrations of suspended solids and fine streambed material, and considerably greater levels of aqueous and particulate phosphorus (P). Primary productivity was much higher in the disturbed system, likely caused by elevated P levels. This study illustrates the potential for logging disturbance to produce long-lived impacts on stream ecology in critical headwater regions.