A joint multidisciplinary investigation was undertaken to study the effects of lime and wood ash applications on two Norway spruce forest Spodosolic soils. The two sites, typical for southern Sweden, were treated in 1994 with either 3.25 t ha-1 dolomite or 4.28 t ha-1 wood ash (Horröd site) or in 1984 with either 3.45 or 8.75 t ha-1 dolomite (Hasslöv site). Both sites show signs of acidification by atmospheric anthropogenic deposition and possessed low soil pH (4.3) and high concentrations of inorganic Al (35 μM) in the upper illuvial soil solution. The prevailing soil conditions indicated perturbed soil processes. Following treatment with lime or wood ash, the soil conditions were amatically altered. Cation exchange capacity (CEC) and base saturation (BS) was considerable increased after addition. Four years after application most of the added Ca and Mg was still present in the more layer. Fifteen years after application, Mg in particular, became integrated deeper in the soil profile with a greater proportion lost by leaching in comparison to Ca. The concentrations of these ions were greatest in the mor layer soil solutions and Mg had higher mobility giving higher concentrations also deeper in the profile. Four years after treatment, the application ofwood ash and lime resulted in lower pH values and higher inorganic Al in mineral subsoil solutions compared to the untreated soil. We hypothesize that this was probably due to an increased flow of hydrogen ions from the upper soil as a result of displacement by Ca and Mg ions in the enlarged exchangeable pool. In contrast, fifteen years after lime and wood ash application, the mineral subsoil horizons possessed a higher pH and lower soil solution Al content than the untreated plots. Liming promoted soil microbial activity increasing soil respiration 10 to 36%. This is in the same range as net carbon exchange for forests in northern Sweden and could potentially have a climatological impact. The turnover of low molecular weight organic acids (LMWOA) by the soil microbial biomass were calculated to contribute 6 to 20% to this CO2 evolution. At Horröd, citrate and fumarate were the predominant LMWOAs with lowest concentrations found in the treated areas. In contrast, at the Hasslöv site, propionate and malonate were the most abundant LMWOAs. Higher microial activity in the upper soil horizons was also the probable cause of the considerably higher DOC concentrations observed in the soil solution of ash and lime treated areas. The lime-induced increase in DOC levels at Hasslöv could be attributed to increases in the 3-10 kDa hydrophobic size fraction. Liming also promoted nitrification with high liming doses leading to extreme concentrations of NO3- (1 mM) in soil solution. At Hasslöv the community of mycorrhizal fungi was dramatically changed by the addition of lime, with only four of 24 species recorded being common to both control and treated areas. Many of the observed effects of lime and ash treatment can be viewed as negative in terms of forest sustainability. After four years of treatment, there was a decrease in the pH of the soil solution and higher concentrations of inorganic Al and DOC. Increased organic matter turnover, nitrification and NO3- leakage were found at Hasslöv. Considering that the weathering rate and the mineral nutrient uptake by trees is most probably governed by mycorrhizal hyphae etching mineral grains in the soil, it is important to maintain this ability of the mycorrhizal fungi. The lime and ash-induced changed mycorrhizal community structure may significantly affect this capability. In light of this investigation and others, as reviewed by Lundström et al. (2003), the implications of liming on forest health are multifaceted with complex relationships occurring over both space and time.