Acid precipitation and soil solution chemistry within a maple-birch forest in Canada

Ion concentrations in water collected within a hardwood forest at Turkey Lakes Watershed, Ont. (Lat. 47° 03′N, Long. 84° 15′W) were examined in relation to those in precipitation at the watershed and at other places in eastern Canada. The mean annual concentration of Ca 2+, Mg 2+, K +, Na +, H +, NH 4 +, NO 3 −, SO 4 2−, Cl − and HCO 3 − in precipitation, throughfall, forest floor percolate and mineral soil solution were evaluated, and the annual flux of H +, NO 3 −, SO 4 2− and base cations was calculated. The annual input of cations by bulk precipitation was only a small proportion (17%) of the flux collected below the forest floor. The deposition of SO 4 2− and NO 3 − in bulk precipitation accounted for 85 and 45%, respectively, of the forest floor fluxes of these ions. The annual flux of H + in throughfall was less than that in precipitation. Calcium and Mg 2+ concentrations in soil solution were highly correlated ( P = 0.05) with NO 3 − during the dormant season and Ca 2+ was highly correlated with SO 4 2− during the growing season. Both SO 4 2− and NO 3 − were largely unreactive with minerals in the Turkey Lakes soil and therefore play a dominant role in cation movement through the soil.