Between the first and second national forest soil inventory in the northeastern German lowlands a significant soil acidification took place with regionally varying intensity. It manifests itself in a reduced base saturation in the whole rooting zone. This applies to the base cations magnesium and calcium. For potassium, however, no significant changes were detected. The acidification dynamic is the strongest in the southern part of Brandenburg. The specific immission situation in this region during the past four decades explains this. Particularly in southern Brandenburg high dust depositions (fly ashes from brown coal-fired power stations) buffered the acid components and enriched the soil with base cations in the 1970s and 1980s. Since the reduction of these atmospheric depositions, the bases were obviously totally incorporated in the biomass or leached out with seepage water. Currently, the majority of the forest sites in Mecklenburg-Vorpommern and Brandenburg are poor in basic nutrient elements (Ca, Mg, K). Especially the element magnesium is assumed to be lacking. This paper presents an assessment of the long-term availability of the nutrients Ca, Mg und K on the basis of calculated nutrient balances for various forest management scenarios (e.g. full-tree harvest). The results show that the sustainable supply is critical especially for intensive forest use on numerous sites.