Figure Captions
Figure 1 . Physical properties of the soil. The soil was sampled at different depths (a), at different slope positions (b), and in different forest types (c). SMC (%), soil moisture content; EC (µs·cm−1), electric conductivity; TDS (µg·L−1), total dissolved solid; GS (g·cm−3), specific soil weight. Forest types: NA,Camellia oleifera new afforestation; GLF, Gardenia jasminoides in a low-yielding C. oleifera forest; LF, low-yielding C. oleifera forest; GNA, G. jasminoides inC. oleifera new afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth. The data are shown as the mean ± SD. (depth and slope positon n = 9forest type n = 12; *P < 0.05, **P< 0.01, ***P < 0.001). Statistical analysis was performed using one-way analysis of variance (ANOVA), and Tukey’s multiple comparison test was used to correct for multiple comparisons.
Figure 2 . General bacterial alpha diversity patterns. Boxplot of alpha diversity indices, including community richness (Ace and Chao) and diversity (Shannon and Simpson). Microbial alpha diversity in the soil samples from different forest types (a), different depths (b), and different slope positions (c). NA, C. oleifera new afforestation; GLF, G. jasminoides in a low-yielding C. oleifera forest; LF, low-yielding C. oleifera forest; GNA, G. jasminoidesin C. oleifera new afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth. OUT, operational taxonomic unit; ACE, abundance-based coverage estimator. The data are represented as a box-and-whisker plot representing median values with interquartile ranges. Different colors indicate different sampling campaigns and sampling locations (depth and slope positon n = 9forest type n = 12; *P < 0.05, **P < 0.01, [Student’s t -test for estimator]).
Figure 3 . Relative abundance of different soil bacteria at the phylum level. Pie chart showing the percentage of species as designated by color (a). In the circos plot, the colors in the left semi-circle represent the species composition, and the outermost circles represent the grouping information. The colors of the inner circles represent species, and the length represents the relative abundance of the species. The right semi-circle indicates the distribution proportion of species in different samples at the taxonomic level for that cluster, the colors of the outermost circles represent species, the colors of the inner circles represent grouping information, and the length represents the fraction of that species in that cluster (b–d). The soil was sampled from different depths (b), slope positions (c), and forest types (d) depth and slope positon (n = 9), forest type (n = 12)). m1 (NA),C. oleifera new afforestation; m2 (GLF), G. jasminoides in a low-yielding C. oleifera forest; m3 (LF), low-yielding C. oleifera forest; m4 (GNA), G. jasminoides in C. oleiferanew afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth. Here, “others” indicates taxa with a maximum abundance of < 0.5% in any sample.
Figure 4 . Bacterial community diversity assessments based on forest type (a), depth (b), and slope position (c) using the Kruskal–Wallis H test bar plot. The image represents the difference between proportions in 95% confidence intervals. “Unclassified” includes all unclassified species obtained directly from the database through sequence alignment. The X-axis represents the average relative abundance of different species, The Y-axis represents the species, and different colors indicate the different groups. NA, C. oleiferanew afforestation; GLF, G. jasminoides in a low-yielding C. oleifera forest; LF, low-yielding C. oleifera forest; GNA,G. jasminoides in C. oleifera new afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth. Depth and slope position (n = 9), forest type (n = 12); *P < 0.05, **P < 0.01
Figure 5 . Principal coordinate analysis (PCoA) of the soil bacterial community composition as affected by forest type (a), depth (b), and slope position (c), and based on the Bray–Curtis distance. Points of the same color belong to the same group, and soil group points that are the same are identified using ellipses. Abscissa represents the first principal component, ordinate represents the second principal component, and the percentage represents the contribution of the principal component to the sample difference. Box plots represent the discrete distribution of the different groups of samples along the PCoA1 axis and different colors represent the different sample groups. Values of R2 and P were calculated using analysis of similarities. NA, Camellia oleifera new afforestation; GLF,Gardenia jasminoides in a low-yielding C. oleifera forest; LF, low-yielding C. oleifera forest; GNA, G. jasminoidesin C. oleifera new afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth.
Figure 6 . LEfSe (LDA effect size) analysis for forest type (a), depth (b), and slope position (c). The colored nodes from the inner to the outer circles represent taxa from the phylum to genus level. The node color denotes different taxa with a more significant role. Taxa without significant differences are labeled in yellow, while significantly different taxa are labeled using the color for each group. A cut‐off value of ≥ 3.0 was used for the linear discriminant analysis (LDA). NA, C. oleifera new afforestation; GLF, G. jasminoides in a low-yielding C. oleifera forest; LF, low-yielding C. oleifera forest; GNA, G. jasminoides inC. oleifera new afforestation. Twenty, soil layer at 0–20 cm depth; Forty, soil layer at 20–40 cm depth; Sixty, soil layer at 40–60 cm depth.
Figure 7 . Correlation between environmental factors and the top 20 most abundant bacterial communities at the phylum level. The X and Y axes represent horizontal and vertical angular environmental factors (species composition), respectively. HC, humus content; GS, specific gravity of solid particles; AP, available phosphorus; TOC, total organic carbon; SOM, soil organic matter; N, soil total nitrogen; C, soil total carbon; NO3–N, nitrate-nitrogen; EC, soil electric conductivity; TDS, total dissolved solid; AK, available potassium; SMC, soil moisture capacity; AN, available nitrogen; NO2–N, nitrite nitrogen; NH4–N, ammonium nitrogen. The red shades represent positive correlation, and the blue shades represent negative correlation. Darker shades represent stronger correlation. (Depth and slope positon (n = 9), forest type (n = 12); *P< 0.05, **P < 0.01, ***P < 0.001.)
Figure 8 . Effects of new afforestation under monoculture and intercropping with G. jasminoides (a) and low-yield forests under monoculture and intercropping with G. jasminoides (b) on bacterial functional communities, as determined using structural equation models. Solid lines indicate that the effects were at a positive level, dashed lines indicate that the effects were at a negative level. The red shades represent positive regulations, and the blue shades represent negative regulations. Darker shades of red represent high regulation strength, and light shades represent low regulation strength. Asterisks indicate the significance level: *P < 0.05, **P < 0.01, ***P< 0.001.)