LONG-TERM TRENDS IN ATMOSPHERIC DEPOSITION AND SEEPAGE OUTPUT IN NORTHWEST GERMAN FOREST ECOSYSTEMS

Long term trends of element fluxes in atmospheric deposition and of co ncentrations in seepage output of seven coniferous and deciduous fores t stands in northwestern Germany have been evaluated for the period 19 81 - 1994. Decreasing deposition rates of SO4 (50 - 70%) and H+ (60 - 80%) occured al all sites concomitant with the decline of SO2 emission rates in the former Federal Republic of Germany. Deposition of Ca, Mg , and K decreased at the Selling and Gottinger Wald stands. During thi s period no consistent trends in the flux rates of NH4 and NO3 were ap parent. Sulfate concentrations in soil solution decreased at the Selli ng and Gottinger Wald stands, whereas an increase occured at Lange Bra mke south slope. As a consequence of reduced deposition and mobile ani on concentrations a decrease of Ca, Mg, K, Al, and Mn in soil solution has been observed at the Selling stands. At the other stands trends o f cations in soil solution are not consistent. Nitrate concentrations in soil solution decreased at the Gottinger Wald. A rising tendency wi th great fluctuations of NO3 concentrations occured at the Selling spr uce stand.