Gert Jan Reinds, Maximilian Posch, Wim de Vries
To evaluate the combined effects of reductions in acid deposition (through abatement strategies for the emissions of SO2 , NOx and NH3) and climate change, an extended version of the dynamic acidification model SMART was applied to Europe. Originally, SMART was developed to evaluate effects of changing acid deposition on the acidification status of the soil. To evaluate effects of climate change scenarios, effects of changes in temperature on geochemical processes such as aluminium dissolution, CaCO3 dissolution and on bio-chemical and biological processes such as mineralisation of organic matter and forest growth, were included. Furthermore, changes in temperature and precipitation affect the results of the hydrological part of the model through a change in computed precipitation excess. Effects of changes in CO2 concentration on e.g. growth and nutrient cycling were not included.
As a basis for the simulations, an overlay was made of 5 different maps: ·
The maps with climate zones and altitude zones are used in the procedure to estimate forest growth. The resulting map contains about 80,000 different units for which computations were made with the model SMART.
Because SMART is a relatively simple one-layer model that does not need long periods of initialisation, the base saturation for poorly buffered soils was initialised using an assumed equilibrium between the base saturation and the steady state soil solution chemistry resulting from atmospheric deposition in 1960. The initial base saturation for well-buffered soils was estimated from the soil type alone because in these soils equilibrium between base saturation and acid deposition is not a realistic assumption. This initialisation procedure has the advantage that, opposite to the "standard procedure" for initialising dynamic acidification models where initialisation is started in pre-industrial times, one does not need to "invent" deposition and uptake scenario's from pre-industrial times onwards (Posch 1998). Accurate historic time series might be available for certain regions, but not for the whole of Europe and not for all compounds. Simulations were made for the period 1960 to 2060; the period between 1960 and 1990 is used 'equilibrate' the model.