The correlation between bacterial communities and physicochemical
characteristics
PCoA showed that the PC 1 axis and PC
2 axis explained 70.19% and 15.96% the difference of bacterial
communities in the samples, respectively (Fig. 3A). The bacterial
communities in the S1, S2, S3, and S4 were clearly separated from those
in the S5, S6, S7 and S8 at PC 1 axis.
ANOSIM analysis also supported the
PCoA result, suggesting that the bacterial communities in the S1, S2, S3
and S4 were significant (p <0.05) different from those
in the S5, S6, S7 and S8 (Fig. 3B).
The same result was obtained from Bray Curtis analysis, which showed
that the distance of bacterial communities in the S1, S2, S3 and S4
sites were wider than those in the S5, S6, S7 and S8 sites.
RDA analysis showed that the sand physiochemical properties explained
80.25% (RDA1 explained 70.78% and
RDA2 explained 9.47%) the variances of bacterial community at the
phylum level (Fig. 4). The sand pH (RDA1 = 96.5%, r2= 0.38, p = 0.01)
and
P (RDA1 = 99.8 %, r2 = 0.38, p =0.019)
significantly positively correlated with RDA1, and altitude (RDA1 =
100%, r2 = 0.50, p = 0.001) and
Ca2+ (RDA1 = 97.2 %, r2 = 0.44,p =0.006) significantly negatively correlated with RDA1,
indicating that these factors were vital to explain the variations of
bacterial community structure. At the OTU level, CCA analysis showed
that the similar correlation between the factors and the bacterial
communities, namely, pH (r2 = 0.49, p =0.002)
and P (r2 = 0.37, p =0.035) significantly
positively correlated with CCA1, and altitude (r2 =
0.55, p = 0.001) and Ca2+ (r2= 0.48, p =0.003) significantly negatively correlated with CCA1,
suggesting that these factors had a similar important effects on
bacterial communities.
VPA analysis showed that both
altitude and pH explained 42.7% of the variations bacterial community.
Ca2+, altitude and pH explained 50.3% of the
variations of the bacterial community. TOC, altitude, and pH explained
46.4% of the variations. EC, altitude, and pH explained 40.4% of the
variations (Fig. S2).
The Spearman correlation analysis was evaluated the correlation between
different phyla and each of the sand physiochemical properties (Fig. 5).
The sand physiochemical properties were divided into two groups. Group 1
included EC, altitude and Ca2+. Group 2 included
Cl-, WC, TOC, Cl, TC, Mg2+, TN,
Na+, V, Zn, Zr, Y, Ti, Mn, pH, and P. Besides, the
bacterial phyla were grouped into three clusters. Cluster 1 was
significantly positively correlated with altitude and
Ca2+ but negatively correlated with V, Zn, Zr, Y, Ti,
Mn, pH, and P. Cluster 2 was significantly positively correlated with
Ca2+, TOC, Cl, Mg2+,
Na+, V, Zr, Y, Ti, Mn, and P, but negatively
correlated with Cl-. Cluster 3 was significantly
negatively correlated with EC, altitude, and Ca2+, but
positively correlated with TC, TN, V, Zn, Zr, Y, Ti, Mn, pH, and P.