RESPONSE OF SOIL SOLUTION CHEMISTRY TO RECENT DECLINES IN ATMOSPHERICDEPOSITION IN 2 FOREST ECOSYSTEMS IN BERLIN, GERMANY

As part of a long-term monitoring program to study the effects of acid deposition on forest ecosystems, throughfall and soil solutions from 50 and 200 cm depth have been collected and analyzed from 1986 to 1995 in a young pine stand and a mixed pine-oak forest in Berlin. Before 1 990, atmospheric SO4 inputs of 1.5-2.1 kmol ha(-1) a(-1) were among th e highest reported for Western Europe. Between 1990 and 1992 they decl ined sharply to below 0.7 kmol ha(-1) a(-1) and continued to decrease until 1995. Most other elements followed a similar time trend, except for mineral-N compounds that decreased by only 30%. The assessment of soil solution reactions to these changes was complicated by high tempo ral fluctuations of solute concentrations in response to soil water co ntent changes. This problem was overcome with a regression model, wher e time-trend corrected Cl concentrations were introduced to account fo r these fluctuations. The data then show that in both stands soil solu tion composition reacts similarly to the changed input situation. Due to the concentration reductions of the major anion SO42- in the soil s olutions, concentrations of most major cations decreased and alkalinit y increased. Still, acidity is transferred to the subsoil, indicating that soil acidification is continuing despite the strongly decreased a cid deposition rates. (C) 1998 Elsevier Science B.V.