Fig. 2.

(a) Gross N mineralization rates and (b) gross nitrification rates measured in bulk soil (open bars) and rhizosphere soil (black bars) of control plots and girdling plots. Significant differences between rhizosphere and bulk soil are indicated by different letters (p < 0.05; letters in brackets indicate significance level of p < 0.1). Significance of differences between control plots and girdling plots for bulk soil and rhizosphere soil, respectively, is indicated by ∗ (p < 0.05) or n.s. (not significant). Error bars represent standard errors (n = 6). n.d. means ‘not determined’.