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, ele ment budgets were established over the period from 1973 to 1991 for a Norway Spruce (Picea abies (L.) Karst.) site. Budgets for Na+, Cl-, Ca 2+, Mg2+, N, S and H+ were based on total deposition and seepage water fluxes. The deposition of Ca2+, Mg2+, particularly, of S and H+ decre ased with time, while calculated N deposition remained constant at a h igh level. The decrease in Ca2+ deposition led to a reduction of Ca2fluxes with seepage water. The decrease of Mg2+ deposition did not hav e an effect on the output fluxes of Mg2+. The reversibility of soil an d seepage water acidification by reduced S deposition was delayed by t he release of previously accumulated soil SO42-. The highest NO3- flux es were observed during the period of 1986 to 1988; NO3- fluxes in gen eral 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 sit e is the aggrading humus layer. The results emphasize the need for mea surements over several years to make conclusions regarding the functio n of ecosystems in response to atmospheric deposition.