The effects of cumulative forest disturbance on streamflow in a large watershed in the central interior of British Columbia, Canada

摘要

The Baker Creek watershed (1570 km2), situated in the central interiorof British Columbia, Canada, has been severely disturbed by both logging andnatural disturbance, particularly by a recent large-scale mountain pinebeetle (MPB) infestation (up to 2009, 70.2% of the watershed area hadbeen attacked by MPB) and subsequent salvage logging. The concept of equivalentclear-cut area (ECA) was used to indicate the magnitude of forestdisturbance, with consideration of hydrological recovery following varioustypes of disturbance (wildfire, logging and MPB infestation), cumulated overspace and time in the watershed. The cumulative ECA peaked at 62.2% in2009. A combined approach of statistical analysis (i.e. time seriesanalysis) and graphic method (modified double mass curve) was employed toevaluate the impacts of forest disturbance on hydrology. Our results showedthat severe forest disturbance significantly increased annual mean flow. Theaverage increment in annual mean flow caused by forest disturbance was 48.4 mm yr?1,while the average decrease in annual mean flow caused by climaticvariability during the same disturbance period was 35.5 mm yr?1. The oppositechanges in directions and magnitudes clearly suggest an offsetting effectbetween forest disturbance and climatic variability, with the absoluteinfluential strength of forest disturbance (57.7%) overriding that fromclimate variability (42.3%). Forest disturbance also producedsignificant positive effects on low flow and dry season (fall and winter)mean flow. Implications of our findings for future forest and waterresources management are discussed in the context of long-term watershedsustainability.