On the niche breadth of Fagus sylvatica:: soil nutrient status in 50 Central European beech stands on a broad range of bedrock types

The soil nutrient status of 50 Central European stands of Fagus sylvatica on 13 acidic to basic bedrock types was investigated with the aim ( i) to define the extremes of important soil chemical and nutrient status parameters tolerated by beech forests, ( ii) to investigate the dependency of these parameters on bedrock type and soil acidity, and ( iii) to analyse the importance of the organic layer for the nutrient status of beech forests. Based on the parameters exchangeable cation pool ( Ca + Mg + K-ex), N/P ratio of the organic layer and C/N ratio of the mineral soil, three nutrient supply classes were identified: ( 1) limestone and claystone soils ( C/N 15-18 mol mol(-1), N/P 20-26 mol mol(-1), ( Ca + Mg + K) ex 5-38 mol m(-2) per 10 cm soil), ( 2) silicate-rich sandstone, tertiary sand, loamy loess and moraine soils ( C/N 20-26 mol mol(-1), N/P 24-45 mol mol(-1), ( Ca + Mg + K) ex 2-3 mol m(-2) 10 cm(-1)), and ( 3) soils derived from silicate-poor sandy deposits ( C/N 28-34 mol mol(-1), N/P 47-59 mol mol(-1), ( Ca + Mg + K) ex 1-3 mol m(-2) 10 cm(-1)). Soil chemical extremes tolerated by beech were 3-99% base saturation, 3.2-7.3 of pH ( H2O), and minima of resin-exchangeable P of 11 mol m(-2), and of ( Ca + Mg + K) ex of 0.4 mol m-2 in the topsoil ( 0-10 cm). A highly variable amount of exchangeable Al in the mineral soil was identified as the key factor controlling the accumulation of C in the organic layer ( OL, OF, OH). Increasing organic layer N/P ratios ( 19 to 59 mol mol(-1)) from basic to acidic soils point at a growing importance of P limitation over N limitation with increasing acidity in beech forest soils.