Browsing by Author "Ulrich, B."

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    A concept of forest ecosystem stability and of acid deposition as driving force for destabilization
    (2007) Ulrich, B.
    A theory is proposed which explains the acidification and alcalinization of soils, respectively, as consequence of the discoupling of the ion cycle in the ecosystem. Under the assumption that the ecosystem tends to minimize net proton production or consumption in order to keep the chemical soil state in optimal conditions for growth, the characteristic features of stable forest ecosystems showing high resilience are deduced. A sequence of ecosystem states is described; aggradation phase, stability range I (high resilience), destabilization phase I (humus disintegration), stability range II (low resilience), destabilization phase II (build up of decomposer refuge, podzoli-zation). A continuous input of acidity exceeding the rate of base cation release by silicate weathering within the root zone forces forest ecosystems from the stability ranges into the transition states (destabilization phases). The concept of stress and strain is used to deduce how acid deposition superimposes natural stress factors and may trigger forest damages connected with climatical extremes and pests.
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    Soil Acidity and its Relations to Acid Deposition
    (1983) Ulrich, B.
    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.