3.3 Soil bacterial community composition
Bacterial phylum with a relative abundance over 8.0% was considered as the dominant phylum in this study. As shown in Figure S2, the dominant bacterial phyla in maize field are Proteobacteria (mean 31.8%),Chloroflexi (mean 14.4%), Actinobacteria (mean 12.1%),Acidobacteria (mean 11.4%), Bacteroidetes (mean 9.2%) and Gemmatimonadetes (mean 5.5%). The relative abundance of bacterial phyla varied significantly in maize field from spring to autumn except Chloroflexi and Patescibacteria (Table S2). For example, Proteobacteria in the maize field along the depth in spring and autumn ranged from 57.1- 22.2% and 47.6% - 15.0%, respectively. Actinobacteria and Bacteroidetes were in the range of 14.6 - 5.2% and 25.8 - 9.7%, 27.6- 2.8% and 11.3 - 1.0%, respectively. Additionally, the relative abundance of the dominant bacterial phyla in the woodland along the depth areProteobacteria (mean 23.2%), Actinobacteria (mean 18.2%), Acidobacteria (mean 17.9%) and Chloroflexi (mean 12.2 %) (Figure S2). Only Actinobacteria, Acidobacteriaand Nitrospirae in the woodland responded significantly to seasonal change (Table S2). For example, Actinobacteria in the woodland along the depth in spring and autumn ranged from 22.2 - 10.9% and 31.8 - 14.1%, respectively. Within the same season, it is quite clear that most of the dominant phyla except Chloroflex andFirmicutes showed significant differences (P < 0.05) between these two land uses in spring, while onlyActinobacteria and Bacteroidetes showed significant difference in autumn. The relative abundance of Bacteroidetesshowed significant differences between different land uses for each season and seasonal difference in the maize field (P < 0.05), but no seasonal difference in the woodlands (P> 0.05).
We further compared the relative abundance of bacterial group (relative abundance > 0.1%) at order level, and found that more bacterial groups showed significant variance between the two land uses in spring than in autumn (Figure 5), indicating that manure addition had a strong impact at the beginning. For example, the relative abundance of Flavobacteriales, Sphingobacteriales and Bacteroidales affiliated withBacteroidetes, Methylococales affiliated withGammaproteobacteria are significantly higher in the maize field than in the woodland in spring (P < 0.05), while no difference was found in autumn. While some bacterial groups showed lower abundance in the maize field than that in the woodland. For example, the relative abundance of Pyrinomonadales affiliated withAcidobacteria , Gaiellales affiliated withActinobacteria , Gemmatimonadales affiliated with Gemmatimonadetes, and Rokubacteriales affiliated withRokubacteria , are significantly lower in the maize field than in the woodland in spring, while there was no difference in autumn.