3.4 Factors driving the distribution of bacterial community structure
We focused on the edaphic factors shaping bacterial community structure between different land uses (Figure 6A) and different seasons (Figures 6B and 6C) with CCA analysis. For different land uses, SOM (R2 = 0.74, P = 0.001), C/N (R2 = 0.70, P = 0.001), NO3--N (R2 = 0.63, P = 0.001), soil pH (R2= 0.57, P = 0.001) and moisture (R2 = 0.53, P = 0.001) were strongly and significantly linked to the variance of bacterial community between different land uses (Figure 6A). All the tested factors except DOC and DON were highly correlated with the seasonal variance of bacterial community structure in maize field (Figure 6B), with SOM (R2=0.81, P=0.001), soil pH (R2=0.61, P = 0.001), NO3--N (R2 = 0.49, P = 0.001) and ammonium (R2 = 0.44, P = 0.001) as the major factors.
In order to reveal phylogenetic community composition, standardized effect sizes of NMTD (ses.MNTD) was calculated. All of the ses.MNTD values obtained using the null model in both land uses were significantly negative (Figure 7), indicating that bacterial assemblages were phylogenetically clustered for all the soils along the depth. Furthermore, the ses.MNTD values showed an increased trend along the depth, indicating that bacterial phylogenetic clustering in the top soil is stronger than those in the deeper soils.