ACID-RAIN AND SOILS OF THE ADIRONDACKS .1. CHANGES IN PH AND AVAILABLE CALCIUM, 1930-1984

Interest in acid rain effects led us to resample 48 Adirondack soil profiles that had been sampled by Carl C. Heimburger in 1930-1932. Changes in pH and dilute-acid-extractable Ca were detected in 1984, which differed by horizon and were dependent on initial conditions. Moderately acidic organic horizons (pH >4.0) showed substantial decreases in pH and extractable Ca, while strongly acidic organic horizons (pH <4.0) showed a significant reduction in extractable Ca without a reduction in pH. The E horizons appeared to lose extractable Ca, while the B and C horizons showed no evidence of acidification. A partial Ca budget for the greater-than-or-equal-to 50-year interval for 16 sites in a mixed hardwood-softwood forest showed that Ca uptake was approximately equal to the loss of Ca from the soil, suggesting that this was a major cause of acidification. Acid-consuming processes apparently balanced acid additions in B and C horizons as no acidification was observed. While acid rain has increased hydrogen-ion loading and base-cation leaching, we did not find evidence of serious impacts on bulk soil chemistry in the Adirondacks through the mid-1980s.