THE IMPACT OF HISTORIC LAND-USE AND MODERN FORESTRY ON NUTRIENT RELATIONS OF CENTRAL-EUROPEAN FOREST ECOSYSTEMS

In the past forests in Central Europe were not only sources of timber and fuelwood but also sources of nutrients to sustain the human population. The use of forests as pastures is still common in some areas while other formerly widespread practices such as litter raking or pollarding have been abandoned. Harvesting of wood, a material of extremely low mineral nutrient content and of wide C/N-ratio depletes nutrients and acid neutralizing capacity at only moderates rates, harvesting of other biomass fractions has a much more severe impact on forest ecosystems. Soil acidification from intensive biomass harvesting of historic land use equaled or exceeded present soil acidification due to the deposition of air pollutants. As a result of historic land use the majority of Central European forest ecosystems was severely depleted of nutrients and acid neutralizing capacity when modern long-rotation forestry became the dominant form of forest land use. At present high deposition rates of acidifying air pollutants prevent the recovery of forest ecosystems in Central Europe. It has to be noted that ecosystem degradation due to excessive biomass harvesting led to systems which were depleted both in nitrogen and acid neutralizing capacity, while high nitrogen deposition rates from Central European air pollution cause a novel combination of progressive soil acidification and concurrent nitrogen saturation. This combination has a high potential for aggravating mineral nutrient deficiencies and nutritional disorders in forest ecosystems.