Acidification of Forest Soils: Model Development and Application for Analyzing Impacts of Acidic Deposition in Europe

Kauppi, P., Posch, M. ORCID: https://orcid.org/0000-0001-8649-9129, Matzner, E., Kauppi, L., & Kaemaeri, J. (1984). Acidification of Forest Soils: Model Development and Application for Analyzing Impacts of Acidic Deposition in Europe. IIASA Collaborative Paper. IIASA, Laxenburg, Austria: CP-84-016

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Abstract

Acidification is considered as an unfavorable process in forest soils. Timber logging, natural accumulation of biomass in the ecosystem, and acidic deposition are known as sources of acidification. Acidification causes the risk of damage to plant roots and subsequent risk of a decline in ecosystem productivity.

A dynamic model is introduced for describing the acidification of forest soils. In one-year time steps the model calculates the soil pH as function of the acid stress and the buffer mechanisms of the soil. Acid stress is defined as the hydrogen ion input into the top soil. The buffer mechanisms counteract acidification by providing a sink for hydrogen ions. The concepts 'buffer rate' and 'buffer capacity' are used to quantify the buffer mechanisms. The model compares (i) the rate of the acid stress (annual amount) to the buffer rate, and (ii) the accumulated acid stress (over several years) to the buffer capacity. These two types of comparisons produce an estimate of the soil pH as the output.

The model was incorporated into a model system for analyzing the acidic deposition problem in Europe. The data on acid stress, entering the soils, was obtained from other submodels which link information on energy production, pollutant emission, pollutant transport, and pollutant deposition. Data on buffer rate and buffer capacity were collected from soil maps and geological maps.

The model system as a whole is now available for analyzing different emission scenarios. The soil acidification model assumes sulfur deposition estimates from the other submodels as the input, and as the output it produces estimates of the pH of European forest soils in a map format. Additionally it computes the total area of forests in Europe with the estimated soil pH lower than any selected threshold value. Sources of uncertainty of the soil acidification model are listed and briefly evaluated.

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