d13C and d18O isotopes were measured from the leaves of shrubs in TSQs. The leaves were collected, dried, milled into a powder, weighed and sent for stable isotope analyses in Jena (Max Planck Institute, Germany).

Leaves were sampled from all shrubs in TSQs. The leaves were dried and milled into a powder. Before weighing the powder for isotope analyses, these vials were placed in an oven at 70°C overnight (without lid) and finally transferred (with lids on) into a desiccator to cool down. A Mettler Toledo XP5 precision scale was used to weigh 0.8-1.1 mg and 0.5-0.6 mg of each sample into tin and silver capsules for δ¹³C and δ¹⁸O, respectively. The capsules were folded and pressed into a cube, using tweezers, and put in the respective position in a plastic trays. The materials were cleaned with 70% ethanol between each sample.

BEF-China experiment, located near Xingangshang, Dexing City of Jianxi Province - Site A and B

Plants (shrubs): Distylium buxifolium (DiBu), Viburnum setigerum (ViSe), Camellia Chemikiangoleosa (CaCh) and Distylium myricoides (DiMy)

The powder was retrieved from another project, using it for many trait measurements, some. For some samples (i.e. TSQs) there was no leaf material left for isotope measurements. These samples, therefore, were excluded: Site B; G26 (0606), N27 (0804), M11 (1613). In addition, during the transportation of the samples 3 labels came off, therefor, the identity of another 3 samples were unknown (Q3, 0117; P22, 1811; J25, 0009).

Cleaning (fixing typos, incorrect label of species etc.). Finding outliers for d13C and d18O and reweighing and measuring, and calculating averages. Combining d13C and d18O data for each species.