| Abstract/Description or Keywords |
The hydrological and chemical characteristics of four small subalpine watersheds in the southern interior of British Columbia were investigated. The watersheds have different forest cover types including mature spruce-fir, lodgepole pine stands 80-140 years of age, and regenerating clear-cut areas with about 15 years of mixed pine, spruce and fir regeneration. Water chemistry of the creeks was found to be typical of gneissic catchments reported in the literature. Concentrations of cations, bicarbonate and silica were controlled by processes occurring in the mineral soil, and were found to decrease with increasing streamflow according to well defined log-normal relationships. Concentrations of hydrogen ion and organic anions were controlled primarily by processes occurring in the forest floor (nitrification, organic matter breakdown), and were found to increase with increasing streamflow. Nitrate was produced within the forest floor. Its concentration was not related to stream discharge, but exhibited pulse behaviour consistent with the 'nitrogen flushing hypothesis.' Sulphate was controlled by a combination of forest floor and mineral soil processes. Water chemistry in the study area is controlled primarily by mineral weathering and forest cover. Differences between the creek containing the regenerating clear-cut and the creeks containing mature timber were consistent with incomplete chemical recovery following forest harvesting, whereas differences in water chemistry between mature timber types could be attributable entirely to air temperature. Analysis of data from 28 watershed studies world-wide showed the effect of forest harvesting on cation budgets to be similar to the short term effect of acid precipitation, although more intense and short-lived. water quality, forest harvest, chemical water quality |
