Carbon and nitrogen concentrations in leaves, fine roots, and soil

Roots were washed in hand-hot water to remove attached soil particles and other material, rinsed with deionised water and transferred into paper bags. Leave, fine root, and soil samples were dried at 60°C for 72 h. First- and second-order roots of each root sample were cut off with scissors and used for analyses (after Pregitzer et al., 2002). Fine roots were ground manually, leaves (without petiole and rachis) and soil were ground with a ball mill (Cornelissen et al., 2003), subsequently dried for another 24 h, and transferred into tin capsules for C and N analyses. Analyses were performed using an elemental analyser (Vario EL II, Elementar Analysensysteme GmbH, Hanau, Germany). C and N concentration is given as relative mass proportion of the element (in %) per sample mass. C:N ratio was calculated from C and N mass proportions.