To determine the importance of Al-availability for soil micro-organisms 95 forest soils from Tyrol/Austria with comparable topography, vegetation, climatic conditions, soil type and with low soil pH (median = 3.9) were investigated for their physical (percentage of stable aggregates, water holding capacity), chemical (pH, electrical conductivity, contents of organic matter, concentrations of easily extractable aluminium, calcium, potassium, magnesium and phosphorus) and microbiological characteristics (microbial biomass and respiration, metabolic quotient, content of ATP, activities of protease and CM-cellulase, cfu-values of total and Al-tolerant bacteria and fungi). A highly significant negative correlation was detected between concentrations of KCl-extractable aluminium and soil pH. By the application of multivariate statistical methods, the effect of the concentration of KCl-extractable aluminium on abundance and activities of soil micro-organisms could be revealed. Al turned out to be of great importance for micro-organisms and often outmatched the significance of other well known soil properties like organic matter, pH or water holding capacity. However, due to very healthy trees at the sites under investigation no effect of Al or soil acidification on forest decline could be detected.

More than 600 arable soils from Flanders (Northern-Belgium) were analysed for their total acid extractable contents of As, B, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in order to determine any increase in the natural background values. Samples were taken at random in several municipalities throughout Flanders. Areas with known historical or actual sources of trace element emissions were omitted although in some cases the distance between those sources and the sampling locations was not more than 20 km. The main soil types were, ranging from north to south: sand, loamy sand, light sandy-loam, sandy-loam and loam. In the coastal area, clay soils (sea polders) were sampled. In addition to the analysis of trace elements, the soil texture class, the pH and the carbon content were determined. Macro- or mesonutrients, Ca, K, P, Mg and Na, were determined from a weak acid extract of the soil samples. Correlations between trace elements and macronutrients provide some information about fertilisation practices and heavy metal sources.A limited number of soils showed slightly enhanced levels for As, Be, Cu, Co, Cr Mn, Ni Pb and Zn. In most cases, this could be linked to the regional industrial activities. However, a clear increase for Cu and Zn, above the natural background could be distinguished in areas with low atmospheric heavy metal deposits. In these cases, the excessive use of animal manure in the past may be the reason for this enrichment. However there was no indication that the Cd content of the soil was raised by the use of large amounts of pig slurry and/or by other common agricultural activities.