LONG-TERM DEVELOPMENT OF ELEMENT BUDGETS IN A NORWAY SPRUCE (PICEA-ABIES (L) KARST) FOREST OF THE GERMAN SOLLING AREA

To evaluate ecosystem response to changing atmospheric deposition, element budgets were established over the period from 1973 to 1991 for a Norway Spruce (Picea abies (L.) Karst.) site. Budgets for Na+, Cl-, Ca2+, Mg2+, N, S and H+ were based on total deposition and seepage water fluxes. The deposition of Ca2+, Mg2+, particularly, of S and H+ decreased with time, while calculated N deposition remained constant at a high level. The decrease in Ca2+ deposition led to a reduction of Ca2+ fluxes with seepage water. The decrease of Mg2+ deposition did not have an effect on the output fluxes of Mg2+. The reversibility of soil and seepage water acidification by reduced S deposition was delayed by the release of previously accumulated soil SO42-. The highest NO3- fluxes were observed during the period of 1986 to 1988; NO3- fluxes in general demonstrated a considerable annual and periodic variation. Total N accumulation in the ecosystem amounted to nearly 590 kg ha(-1) yr(-1) during the observation period, The major sink of N in the spruce site is the aggrading humus layer. The results emphasize the need for measurements over several years to make conclusions regarding the function of ecosystems in response to atmospheric deposition.