Soil Acidity and its Relations to Acid Deposition

Abstract

The nature of soil acidity as well as measures of the capacity and the intensity terms are discussed. According to the proton buffer reactions occuring in soils, buffer ranges are distinguished. They are defined by pH values. Forest soils on limestones which should be in the calcium carbonate buffer range, acidify under the influence of acid deposition as soon as the fine earth is free of calcium carbonate. The same may be true for soils staying in the silicate buffer range if the rate of acid load exceeds the rate of acid buffering by base cation release during silicate weathering. From existing data on the rate of acid deposition in Central Europe, it is concluded that soils staying in the cation exchange buffer range should have lost considerable amounts of exchangeable Ca due to acid deposition since beginning of industrialization. The resilience of the ecosystem becomes very limited if the soil stays with all major horizons in the aluminium or even in the iron buffer range. The iron buffer range is characterized by podzolization.