APPLICATION OF THE SAFE MODEL TO A NORWAY SPRUCE STAND AT BALLYHOOLY,IRELAND

Acid rain results in qualitative and quantitative changes in terrestri al ecosystem boundary conditions. Typically these changes exceed the r ange of variation observed or inferred from past states. Methods of pr edicting future states are required, such as process-based models or e xperimental treatments that mimic future scenarios. The dynamic biogeo chemical model SAFE was applied to Ballyhooly intensive forest monitor ing plot located in southern Ireland. SAFE is a dynamic, process-orien ted soil chemistry model developed with the objective of studying the effects of acid deposition on soils and groundwaters. It calculates th e values of different chemical state variables as a function of time. The model requires input data on soil mineralogy, soil texture, CEC an d base saturation, together with time-series data for atmospheric depo sition, nutrient uptake and cycling, and hydrology. Model results indi cate that the basic principles in the model are capable of describing the present soil-solution chemistry at Ballyhooly without extensive ca libration. However, the gibbsite equilibrium model does not describe t he observed concentrations of aluminium at Ballyhooly, and the assumpt ion that sulphur adsorption is insignificant appears also to be incorr ect. Inclusion of processes such as sulphur adsorption, aluminium comp lexation with organic matter, or a kinetic-based aluminium model may i mprove model results. (C) 1998 Elsevier Science B.V.