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Ionic Composition of Sagehen Creek, California, Following an Adjacent Fire

Johnson, C. M., Needham, P. R.
Ecology 1966 v.47 no.4 pp. 636-639
basins, bicarbonates, calcium, cations, forest fires, forest soils, magnesium, pH, potassium, rain, runoff, seasonal variation, snow, sodium, springs (water), stream flow, streams, summer, California
Samples of water from Sagehen Creek, California, were collected at 2—week intervals for 2 years following the Donner Ridge forest fire which burned over the lower part of Sagehen Basin in 1960. Sampling sites included a spring which feeds the stream above the burned area and two sites in the stream, one above the burned area below the spring, the other within the burned area. Analyses included pH, bicarbonate, calcium, magnesium, sodium, and potassium. Seasonal variation in ionic composition was observed at both stream sampling sites. In contrast to the constant composition of the spring water for the 2—year period, the summer, streamflow was low and stream ionic concentrations equalled or exceeded those of the spring water. During periods of runoff snow, March to June streamflow increased greatly and ionic concentrations decreased. There was no specific effect of the fire on the ionic composition of the stream. It is postulated that ash constituents were dissolved by light rainfall and leached into the permeable forest soil before the first snow. Because of the acidic nature of the soil the dissolved cations were absorbed on the exchange complex rather than washed directly into the stream.