Figure 2. δ¹⁸O and δ²H values of xylem water before and after the labeling.

δ¹⁸O (top) and δ²H (bottom) values are given for the background samples and the samples taken after the labeling at three different times (April, June, September 2011) in each case pooled for all species richness levels. Outliers (at δ¹⁸O = 141.7 ‰ and δ²H = 101.3 ‰ in June and at δ¹⁸O = 187.3 ‰ in September) were removed for reasons of clarity. Results of the corresponding mixed-effects models are given in the running text. Significant differences among the background samples and the samples taken after labeling are indicated with asterisks (with *** referring to P < 0.001).