Modelling Al-solubility controls in an acid forest soil, Solling, Germany

Hypotheses for controls of the Al solubility in acid forest soils were tested, using the large data set of soil- and solution chemistry of the Solling Spruce site (Germany). The observed low Al3+-H+ reaction stoichiometries (±0.3) as well as the measured increase of CEC in the surface soil with time, support the hypothesis of Al solubility control by complexation to soil organic matter (SOM). Incorporation of SOM-Al equilibrium in a comprehensive soil acidification model improves simulations of seasonal and long-term pH changes in soil solutions at Solling.