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

Forests in southern Sweden are exposed to acidic deposition, which may ulti mately become detrimental to the vitality and growth of the forests. The ai m of the present work was to study the leaching of a range of physiological ly important ions after different treatments representing high loads of N a nd other acidifying substances, as well as the effects of treatments aimed to counteract soil acidification (additions of lime, ash and vitality ferti lizer). We compared the leaching from two types of lysimeters ("ingrowth" w ith, and "trenched" without, active tree roots) at two sites in the south a nd two sites in the north of Sweden. Generally, considerably larger amounts of ions were leached from trenched than ingrowth cores, and from the south ern as compared to the northern sites. Additions of N caused, in the presen ce of tree roots, increased leaching of inorganic N in the north, and in th e south of not just N, but also Ca, Mg, Mn and Al. Liming caused increased NO3- leaching only in the absence of roots at an N-rich site. Indications o f soil Mg depletion were found after limestone addition. Vitality fertilize r caused no change in the leaching of ions in ingrowth cores. The study emp hasizes 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. (C) 2001 Elsevier Science B.V. All rights reserved.