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.