Showing Shannon’s diversity indices of the metabolically active and total diazotrophic bacteria and the total bacterial communities derived from the DGGE analyses.

The nifH mRNA transcripts are represented by the top, the nifH gene by the middle and the 16S mRNA transcript by the bottom panels respectively. Bars labelled with the same letter in the same year are not different (P = 0.05). Bars are standard errors (n = 16).