Optima 3000 icp spectrometer

One important functional trait, i.e. leaf tensile strength, was measured from green leaves of the respective species. We always collected fresh, mature, non-senescent sun leaves without significant herbivory symptoms to measure leaf tensile strength for all species [40 (link)]. The leaf tensile strength, termed as leaf toughness in our study, was measured as the force needed to break the leaf, expressed by per unit of width of a leaf sample rather than per cross-sectional area, thus incorporating leaf thickness as a component of tensile strength (unit: N cm^-1). The measurements were taken following [41 (link)]. Moreover, litter chemical traits were measured on the initial litters and decomposed litters respectively. These included C, N, P, S, K, Ca, Mg, Mn, Fe and Zn. The C and N concentrations were determined by oven drying the litter at 75°C overnight with subsequent grinding using a modified ball mill [42 (link)]. The ground plant materials were analyzed on an automated elemental analyzer. The other element concentrations were analyzed by inductively coupled plasma emission spectroscopy (Perkin Elmer Optima 3000 ICP Spectrometer, Waltham, MA).

We measured water nutrient concentrations both before and after litter submergence. For nutrient analysis, we used a Smart-Chem spectrophotometer (WESTCO Scientific Instruments, Brookfield, CT, USA) to measure the concentrations of total nitrogen (TN), total phosphorus (TP), nitrite nitrogen (NO₃-N) and ammonium nitrogen (NH₄-N). Moreover, the total carbon and total nitrogen concentrations of the litter were analyzed by an automated elemental analyzer. P concentrations in litter were analyzed by inductively coupled plasma emission spectroscopy (Perkin Elmer Optima 3000 ICP Spectrometer, Waltham, MA). In addition, we used a multi-parametric probe (YSI 6820, YSI Environmental Inc., USA) to measure water temperature, dissolved oxygen, electrical conductivity and total dissolved solids during litter submergence.