Canopy closure was quantified for each plot by taking a hemispherical photograph 1 m above ground in the centre of each plot with a fish-eye lens (Nikon, Fisheye Converter FC-E8 0.21x, Japan). The photos were analysed using Gap Light Analyzer 2.0 (Cary Institute of Ecosystem Studies, 1999). Five samples of the upper mineral horizon were randomly taken in each plot and pooled to determine pH (H2O) value, base saturation and the C/N ratio using standard procedures (see Steubing and Fangmeier, 1992). Soil nitrogen and carbon content were determined with a CN-analyser (Elementaranalysator Vario El Cube, Hanau, Germany).
Observation (Field)
Experiment (Laboratory)