Contrasting Stream Water NO super(-) sub(3) and Ca super(2+) in Two Nearly Adjacent Catchments: The Role of Soil Ca and Forest Vegetation

To elucidate factors affecting the variability in stream water concentrations, soil and forest floor samples from each subcatchment for total elemental cations and extractable N species were analyzed. Mineral soil samples were also analyzed for exchangeable cations. Tree species composition was characterized in each subcatchment and potential differences in land use history and hydrology were also assessed. The soils in S14 had significant higher total elemental Ca super(2+) in the forest floor, Bs horizon and C horizon. The exchangeable Ca super(2+) was also significantly higher in the mineral soil. The total basal area of base-rich indicator tree species was significantly greater in S14 compared with S15, which had species characteristic of sites with lower base concentrations. The marked difference in soil Ca super(2+) concentrations in S14 vs. S15 corresponded to the higher stream water Ca super(2+) and the larger contribution of base-rich tree species to the overstory biomass in S14.