Citation | Hudson, R and Tolland, L. 2002. Roberts Creek Study Forest: effects of partial retention harvesting on nitrate concentration in two S6 creeks three years after harvesting. Forest Research Technical Report TR-019. Vancouver Forest Region. |
---|---|
Organization | FLNRO |
URL | https://www.for.gov.bc.ca/rco/research/projects/rcsf/TR019.pdf |
Abstract/Description or Keywords | The Flume Creek Paired Watershed Experiment (Roberts Creek Study Forest, Sunshine Coast, BC) was implemented in the early 1990s to provide information on the effects of forest harvesting on drinking water quality. Three study creeks were identified: F4 (39 ha catchment area), F5 (61 ha) and F6 (16 ha). The study creeks have been monitored for streamflow more or less continuously, using high frequency event based automatic sampling to obtain detailed water quality data. Variable retention (VR) and strip shelterwood treatments were applied to F4 and F5 respectively, in two stages. In the summer of 1998, about half of the target volume on each creek was harvested; the remainder of the cut was taken in summer 1999, leaving F4 and F5 at 39% and 17% harvested. F6 was kept as the control creek. This divided the data into four periods: prelogging, year 1 (the logging phase following the first entry) and years 2 and 3 (one and two years after logging). Prior to treatment, nitrate concentration exhibited pulse behavior with the highest concentrations occurring just after fall freshet. Subsequent storms produced nitrate pulses of diminishing concentration as the season progressed. Several parameters were used to assess the changes in nitrate status following logging, including arithmetic and flow-weighted mean concentration, seasonal nitrate flux, and change in peak concentration of paired nitrate pulses relative to the control. Ratios of each parameter for treatment periods relative to control periods were calculated. Overall, nitrate levels at F5 were about 4, 30 and 60 times that of its unlogged state in years 1, 2 and 3 respectively, while at F4 the nitrate levels changed by factors of 12 and 18 times in years 2 and 3, and were unchanged in year 1. These results are somewhat unexpected. It had been thought that F4 would experience a larger change in nitrate concentration than F5, proportional to harvesting intensity. Instead, the change in nitrate levels at F5 were 3 times the changes at F4. Therefore, the response is likely due in part to differences between the watersheds as opposed to purely a treatment effect. It is speculated that the riparian zone of F5 stores more nitrate than that of F4, and that the large response in water chemistry is due to riparian disturbance. |
Information Type | report |
Regional Watershed | sunshine coast |
Sub-watershed if known | Flume Creek |
Aquifer # | |
Comments | |
Project status | complete |
Contact Name | |
Contact Email |