Fig. 2

Abundance of ammonia oxidizers in tea field soil. Abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (β-AOB and γ-AOB) estimated from ammonia monooxygenase subunit A (amoA) gene copies in tea field soil samples from (a) site 1, (b) site 2, and (c) site 3 at Kanaya Tea Research Station, Shizuoka. Error bars represent the SD for triplicate samples. Different letters above bars indicate significant differences among nitrifiers in each soil layer according to Tukey’s HSD test (P < 0.05, n = 3). No statistically significant differences were observed among soil layers for AOA in site 1 (F(5,12) = 0.76, p = 0.60), site 2 (F(5,12) = 0.17, p = 0.97), and site 3 (F(5,12) = 1.38, p = 0.30). Similarly, no significant differences were detected among soil layers for γ-AOB in site 1 (F(5,12) = 2.41, p = 0.10) and site 2 (F(5,12) = 1.95, p = 0.16), as determined by one-way ANOVA.