Terrestrial ecosystem recovery - Modelling the effects of reduced acidic inputs and increased inputs of sea-salts induced by global change

The reduced emissions of acidifying sulfur and nitrogen in Europe since the late 1970s will be further reduced when the Gothenburg protocol is fully implemented by 2010. Here we address the consequences for the recovery of acidified terrestrial ecosystems using the acidification model MAGIC applied to 3 large-scale "clean rain" experiments, the so-called roof experiments at Risdalsheia, Norway; Gardsjon, Sweden, and Klosterhede, Denmark. Implementation of the Gothenburg protocol will initiate recovery of the soils at all 3 sites by rebuilding base saturation. The rate of recovery is small and base saturation increases less than 5% over the next 30 years. A climate-induced increase in storm severity will increase the sea-salt input to the ecosystems. This will provide additional base cations to the soils and more than double the rate of the recovery, but also lead to strong acid pulses following high sea-salt inputs as the deposited base cations exchange with the acidity stored in the soil. Future recovery of soils and runoff at acidified catchments will thus depend on the amount and rate of reduction of acid deposition, and in the case of systems near the coast, the frequency and intensity of sea-salt episodes as well.