Water Chemistry Profiles under Four Tree Species at Gisburn, NW England

A study was made of the changes and variation in the chemistryof rainwater passing through the different strata of separateecosystems of four tree species (oak, alder, spruce and pine)on the same site at Gisburn (Bowland Forest), north-west England.Waters were sampled as rain, throughfall, forest-floor leachateand soil waters from both the A and B/C horizons; and analysedfor NH₄-N, NO₃-N, PO₄-P, K, Ca, Mg, Na, Al, SO₄-S, Cl, totalorganic carbon and pH. Species differences — often markedones — appear to exist in the concentrations of most solutesin most strata. The between-species differences in throughfallchemistry provide little guide to the chemistry of waters lowerdown the profile: the forest floor is a particularly importantsource of further species differences, e.g. variation in NO₃production and the resulting effects on acidity and other ions. The chemistry of the soil waters provides some indication ofpossible drainage losses, although the question of which horizonacts as the source of drainage waters on this site remains unanswered.The levels of H and Al, in particular, are very different betweenthe upper mineral soil (A horizon) and the lower B/C horizon.In general, and based on these concentration data only, oakis associated with smallest potential solute losses, pine thegreatest. Received 13 February 1990.