Fig. 2.

Histograms and box-and-whisker plots for ɛ_SOM/31 from published δ¹³C_SOM and δ¹³C₃₁ values from subtropical and tropical regions (SI Appendix). Published data are binned at 0.5‰ intervals (counts) based on site averages. Values for δ¹³C_SOM (dark gray) and δ¹³C₃₁ (light gray) are plotted relative to δ¹³C_leaf. Values of ɛ_SOM/31 equal about 9‰ in both C₃ and C₄ ecosystems. Individual boxes contain interquartile ranges (IQRs). Bold vertical lines within boxes mark median values. ○, mean values. Horizontal whiskers mark minimum and maximum values, except values outside of 1.5 IQR (●). Notch half-width values indicate confidence in differentiating median values.