Ion leakage after liming or acidifying fertilization of Swedish forests — a study of lysimeters with and without active tree roots

Abstract

Forests in southern Sweden are exposed to acidic deposition, which may ultimately become detrimental to the vitality and growth of the forests. The aim of the present work was to study the leaching of a range of physiologically important ions after different treatments representing high loads of N and other acidifying substances, as well as the effects of treatments aimed to counteract soil acidification (additions of lime, ash and vitality fertilizer). We compared the leaching from two types of lysimeters (“ingrowth” with, and “trenched” without, active tree roots) at two sites in the south and two sites in the north of Sweden. Generally, considerably larger amounts of ions were leached from trenched than ingrowth cores, and from the southern as compared to the northern sites. Additions of N caused, in the presence of tree roots, increased leaching of inorganic N in the north, and in the south of not just N, but also Ca, Mg, Mn and Al. Liming caused increased NO 3 − leaching only in the absence of roots at an N-rich site. Indications of soil Mg depletion were found after limestone addition. Vitality fertilizer caused no change in the leaching of ions in ingrowth cores. The study emphasizes the importance of tree root uptake, i.e. of healthy forest stands, to counteract the acidifying leaching of base cations, as well as Al and NO 3 − from mineral soils.