Recovery of soil pH, cation-exchange capacity and the saturation of exchange sites from stemflow-induced soil acidification in three Swedish beech (Fagus sylvatica L.) forests

Stemflow water acidifies the soil in beech stands impacted by atmospheric deposition. To investigate whether the soil recovers from acidification, stemflow was experimentally removed. A horizon material was sampled at a distance of 10-250 cm From the stems. Before the onset of the experiment, there were stemflow-induced gradients in the saturation of exchange sites with K+, H+ and Na+ that were larger near the stems, while the pH(KCl), the cation-exchange capacity, and the saturation with Ca2+, Mg2+ and Mn2+ were smaller. After 8 yrs of recovery, the pH(KCl) and the saturation with Ca2+ and Mg2+ had increased close to the stems, while the saturation with Na+, H+, Mn2+ and Fe2+ and the C/N ratio had decreased. With some exceptions, e.g. base saturation, the recovery was not complete after 8 yrs. Soil far from stems had also changed similarly, probably because of the ongoing decrease in overall deposition in southern Sweden.