A very simple dynamic soil acidification model for scenario analyses and target load calculations

A very simple dynamic soil acidification model, VSD, is described, which has been developed as the simplest extension of steady-state models for critical load calculations and with an eye on regional applications. The model requires only a minimum set of inputs (compared to more detailed models) and execution time is minimised by reducing the set of model equations to a single non-linear equation. To facilitate the exploration of model behaviour at individual sites, the model is linked to a graphical user interface (GUI). This GUI allows easy (Bayesian) calibration, forward simulation (scenario analyses) and can also be used to compute target loads and delay times between deposition reductions and ecosystem recovery. VSD compares well to other widely used more complex models and is currently used in several European countries in the support of effects-based emission reduction policies.