FIGURE 3 Bacterial communities in the core rhizosphere of
different samples. The inner (various colors) and outer (yellow)
pie charts represent the core
bacterial phyla and genera, respectively. The size of each phylum and
genus in the pie chart represents their contribution to the overall
abundance. The box plots show the relative abundance of the
corresponding genus in the different samples. Some genera appeared in
the taxonomy database with no corresponding scientific name and are
labeled ‘norank’.
3.6 | Relationships between the rhizosphere
microbial community and soil environmental factors
The RDA results show that for bacteria, the first axis explained 53.97%
of the variation in the data, and the second axis explained 14.06%,
representing a cumulative explanatory power of 68.03% (Figure 4A). The
first two axes reflected the relationships between the genera and their
influencing factors well. As shown in Figure 4A, norank_Subgroup
2 had the strongest correlation with environmental factors, whilenorank_Gemmataceae had the weakest correlation. On the other
hand, Acidothermus was greatly affected by the total organic
carbon, total nitrogen content and C/N but was less affected by pH and
soil moisture. Norank_Xanthobacteraceae andnorank_Acidobacteriales had strong positive correlations with pH
and soil moisture and weak correlations with altitude,
total organic carbon, total nitrogen
and C/N. For the fungi, Figure 4B shows that the first axis explained
35.27% of the variation, and the second axis explained 27.06%,
representing a cumulative explanatory power of 62.87%. Of the top 10
fungal genera, unclassified_Basidiomycota andunclassified_Fungi showed strong positive correlations with
total organic carbon, total nitrogen, moisture, C/N and pH, as didSebacina .
The heatmap results show that, for the bacteria, there was a very
significant positive correlation between norank_Subgroup2 and
soil moisture (P<0.01). There was a significant negative
correlation between norank_Elsterales and pH (Figure 4C). OfAcidibacter , Acidothermus and Bryobacter , the three
confirmed genera, Bryobacter had a significant negative
correlation with pH and moisture (P<0.05), andAcidothermus showed a significant positive correlation with total
organic carbon and total nitrogen. For the fungi, there was a
significant positive correlation between Sebacina and total
organic carbon and total nitrogen (P<0.05). There was a
significant negative correlation between Saitozyma and soil pH
(Figure 4D). The other microorganisms showed different degrees of
positive and negative correlation with environmental factors, but none
of these correlations were significant. The analysis results shown in
the heatmap are consistent with the RDA.