SOIL ACIDIFICATION - COMPARISON OF ACID DEPOSITION FROM THE ATMOSPHERE WITH INPUTS FROM THE LITTER SOIL ORGANIC LAYER

At three relatively unpolluted sites in beech (Fagus sylvatica) woodla nds on the Chiltern Hills of southern England, measurements were made over one year of the amount and composition of precipitation, throughf all, stemflow, and drainage below the soil organic layer. At two sites the soils were acidic and at the third the soil contained calcium car bonate. Comparison was made between the soil acidification potential ( A.P.) of throughfall calculated as (H+ + 2NH(4)(+)) and the A.P. of th e drainage water from the soil organic layer calculated as the differe nce between the sum of cations and the sum of Cl-, SO42- and N-3(-), t hat is, as HCO3- + organic anions. In the two woodlands with acidic so il the A.P. of throughfall was 198 mmol(c) m(-2) a(-1) and that of the drainage water was 224 mmol(c) m(-2) a(-1); the corresponding figures for the woodland with calcareous soil were 176 and 511 mmol(c) m(-2) a(-1). The increases in the drainage water are attributed mainly to or ganic anions in the acidic soils and bicarbonate in the calcareous soi l. The relative importance of the components in throughfall and the or ganic anions in drainage from the soil organic layer is discussed in r elation to soil acidification.