Forest damages by the storm 'Lothar' in permanent observation plots in Switzerland:: The significance of soil acidification and nitrogen deposition

In a network of permanent observation plots in Switzerland, the storm 'Lothar' uprooted 18.7% of Fagus sylvatica and 14.8% of Picea abies. The percentage of uprooting was significantly inversely correlated with actual soil base saturation (NH4Cl-extract). At a base saturation of less than or equal to40% (calculated as an average over 0-40cm depth) uprooting was increased by a factor of 4.8 in beech and by a factor of 3.6 in Norway spruce compared to less acidic soils. In beech, the percentage of uprooted trees was also significantly correlated with nitrogen concentration in the leaves (positively) and with coarse pore volume in the soil (negatively). There was neither a relation with seasonal ozone dose nor a relation with crown transparency, stem diameter, crown. size, slenderness, social position and position within the stand. The results suggest that anthropogenic stress factors play an important role in the extent of the 'Lothar' damages in Switzerland.