2.6 | Data processing
The similarities and differences between the samples were based on operational taxonomic unit (OTU) clustering, and representative sequences in the OTU clusters were obtained. The most abundant sequences were selected as representative OTUs and used in various OTU analyses. The soil bacteria alpha diversity was calculated after randomly subsampling sequences to an equal number. Four metrics were used for alpha diversity analysis, namely the observed species richness (Chao) index, abundance-based coverage estimator (ACE) index, Shannon index, and Simpson’s index (Prober et al., 2015; Gao et al., 2018). To analyze the species turnover, we calculated the Bray–Curtis dissimilarity for the same subplot with different forest types, slope positions, and depths. Principal coordinate analysis (PCoA) of the β-diversity was calculated based on the Bray–Curtis algorithm. The structure equation model (SEM) was used to assess the direct effects of planting G. jasminoides in C. oleifera on soil physicochemical properties and soil bacterial characteristics (He et al., 2020).The data were analyzed using the free online Majorbio Cloud Platform (www.majorbio.com). Statistical differences were tested by ANOVA.