Results
Physicochemical characteristics
of sand samples
In the surface sand samples, the physicochemical parameters displayed
significant differences (P < 0.05), except Zn and TC,
(Table 1 and Table S2). The pH, altitude, Ca2+, P and
Y showed highly significant differences (P < 0.001).
In the subsurface sand samples, the
physicochemical parameters exhibited significant differences (P< 0.05) except WC, EC, TN, TOC, Cl-,
Mg2+ and Cl, (Table 1 and Table S2). The altitude, P,
Ti, Mn, V and Y showed highly significant differences (P< 0.001). Overall, the soil pH and altitude significantly
decreased from north to south (P < 0.05). Furthermore,
the physicochemical parameters of surface sand were similar to that of
the subsurface sand, except the WC and Y levels which exhibited
significant differences between the surface and subsurface samples.
Variations of bacterial
communities in the samples
16S rRNA gene sequencing generated a total of 2160932 sequences after
quality control. The sequences were classified into 5,195 OTUs at the
97% similarity level. In the surface samples, the Shannon index, Chao
index, Simpson index, Sobs index and Ace index of the samples ranged
from 0.807 to 3.044, from 151 to 312, from 0.133 to 0.807, from 138 to
278, and from 151 to 319, respectively (Table 2). Shannon and Simpson
indices showed significant differences in the surface samples. In the
subsurface samples, the Shannon index, Chao index, Simpson index, Sobs
index and Ace index of the samples ranged from 0.790 to 4.111, from 158
to 431, from 0.058 to 0.816, from 137 to 335, and from 149 to 427,
respectively. All of these indices showed significant differences in the
subsurface samples. No significant differences were observed between the
surface alpha diversity and that of the subsurface.