Figures (5)  Tables (1)

    • Figure 1. 

      Effects of tree species mixtures on the P fractions in (a) bulk, and (b) rhizosphere soil. Data are presented as means ± 95% confidence intervals. Asterisks indicate significant mixture effects: ** p < 0.01; *** p < 0.001. BM, bulk soil in mixed plantations; RMC, rhizosphere soil of Cunninghamia lanceolata in mixed plantations; RMP, rhizosphere soil of Phoebe bournei in mixed plantations.

    • Figure 2. 

      Effects of tree species mixtures on gene abundance and diversity of phoD- and pqqC-harboring bacterial communities in (a) bulk, and (b) rhizosphere soils. Data represent means ± 95% confidence intervals. Significant differences are marked with asterisks: * p < 0.05; ** p < 0.01; *** p < 0.001. NMDS ordination based on Bray–Curtis dissimilarity illustrating compositional shifts in (c) phoD- and (d) pqqC-harboring communities across forest types and soil compartments. BM, bulk soil in mixed plantations; BP, bulk soil in monocultures; RMC, rhizosphere soil of Cunninghamia lanceolata in mixed plantations; RMP, rhizosphere soil of Phoebe bournei in mixed plantations; RPC, rhizosphere soil of Cunninghamia lanceolata in monocultures.

    • Figure 3. 

      Manhattan and ternary plots of enriched ASVs in phoD- and pqqC-harboring bacterial communities within (a), (c) bulk, and (b), (d) rhizosphere soils across forest types. Point size corresponds to mean relative abundance. Colors indicate significant enrichment (Kruskal–Wallis test, p < 0.05). BM, bulk soil in mixed plantations; BP, bulk soil in monocultures; RMC, rhizosphere soil of Cunninghamia lanceolata in mixed plantations; RMP, rhizosphere soil of Phoebe bournei in mixed plantations; RPC, rhizosphere soil of Cunninghamia lanceolata in monocultures.

    • Figure 4. 

      Relationships between (a), (c) phoD-, and (b), (d) pqqC-harboring bacterial communities and soil P fractions, evaluated using Mantel tests and distance-based redundancy analysis (dbRDA) with Bray–Curtis dissimilarity. Percentages in parentheses indicate variance explained per axis. (e) Bar plot shows individual contribution of each P fraction.

    • Figure 5. 

      Optimal models depicting effects of plant properties, soil properties, and microbial traits on labile P in (a) bulk, and (b) rhizosphere soils. Bars represent mean parameter estimates with 95% confidence intervals. Piecewise structural equation models (SEM) illustrate direct and indirect effects on labile P in (c) bulk, and (d) rhizosphere soils. Values below boxes denote explained variance (R2); path coefficients are shown alongside arrows. Significance levels: * p < 0.05; ** p < 0.01; *** p < 0.001. AGB: aboveground biomass; AN: available nitrogen; SOM: soil organic matter; TP: total phosphorus; ALP: alkaline phosphatase; ACP: acid phosphatase.

    • Parameters BM BP RMC RMP RPC p-value of linear mixed models
      Forest
      type      		 Soil
      compartments      		 Type ×
      compartments      		 Block
      Labile P
      Resin-P (mg·kg−1) 6.03 ± 0.81 d 6.20 ± 0.69 d 12.64 ± 0.92 c 15.54 ± 1.02 a 14.27 ± 0.75 b 0.500 < 0.001 < 0.001 0.994
      NaHCO3−Pi (mg·kg−1) 12.98 ± 1.91 b 10.64 ± 0.70 b 39.36 ± 2.85 a 39.63 ± 2.06 a 37.11 ± 1.71 a 0.628 < 0.001 < 0.001 0.995
      NaHCO3−Po (mg·kg−1) 51.40 ± 5.61 a 26.25 ± 3.09 c 42.64 ± 3.53 b 49.03 ± 2.45 a 38.11 ± 3.55 b < 0.001 0.655 < 0.001 0.934
      Moderate labile P
      NaOH-Pi (mg·kg−1) 22.21 ± 1.84 d 19.03 ± 1.70 d 40.93 ± 3.08 b 48.36 ± 2.27 a 35.72 ± 2.47 c 0.199 < 0.001 < 0.001 0.976
      NaOH-Po (mg·kg−1) 150.22 ± 6.01 a 92.52 ± 2.92 d 104.92 ± 4.35 c 129.25 ± 6.75 b 102.22 ± 5.47 c < 0.001 0.021 < 0.001 0.987
      HCl-P (mg·kg−1) 7.85 ± 0.93 c 6.91 ± 0.82 c 17.42 ± 1.58 b 22.37 ± 1.13 a 18.42 ± 1.71 b 0.989 < 0.001 < 0.001 0.991
      Stable P
      HCl-Pi (mg·kg−1) 172.21 ± 10.04 c 121.45 ± 4.06 d 162.67 ± 3.83 c 199.68 ± 8.69 b 225.26 ± 5.30 a 0.655 < 0.001 < 0.001 0.999
      HCl-Po (mg·kg−1) 110.65 ± 14.92 b 318.32 ± 19.03 a 67.48 ± 7.93 c 81.98 ± 4.43 c 81.89 ± 4.08 c < 0.001 < 0.001 < 0.001 0.996
      Residual-P (mg·kg−1) 87.53 ± 3.03 c 99.74 ± 5.15 a 99.40 ± 6.61 a 97.11 ± 4.02 ab 90.85 ± 4.57 bc 0.464 0.550 < 0.001 0.782
      Chemical properties
      pH 4.63 ± 0.06 a 4.54 ± 0.06 b 4.39 ± 0.13 c 4.62 ± 0.04 a 4.42 ± 0.08 bc 0.337 < 0.001 < 0.001 0.892
      SWC (%) 17.52 ± 0.76 a 17.56 ± 1.88 a 15.06 ± 1.06 b 15.22 ± 0.95 b 14.97 ± 1.19 b 0.968 < 0.001 < 0.001 0.707
      AN (mg·kg−1) 127.75 ± 17.55 b 105.00 ± 13.36 c 149.80 ± 15.81 a 158.20 ± 14.90 a 100.10 ± 12.07 c < 0.001 0.312 < 0.001 0.699
      SOM (g·kg−1) 31.58 ± 3.58 bc 25.88 ± 3.81 cd 41.86 ± 5.18 a 37.46 ± 4.71 ab 23.22 ± 4.22 d < 0.001 0.181 < 0.001 0.859
      TC (g·kg−1) 17.13 ± 2.05 b 12.43 ± 2.19 c 23.02 ± 3.42 a 21.59 ± 2.52 a 14.47 ± 3.56 bc < 0.001 0.015 < 0.001 0.930
      TN (g·kg−1) 1.44 ± 0.18 ab 1.21 ± 0.16 b 1.70 ± 0.28 a 1.68 ± 0.17 a 1.18 ± 0.22 b < 0.001 0.250 < 0.001 0.836
      TP (g·kg−1) 0.58 ± 0.04 c 0.66 ± 0.06 bc 0.63 ± 0.10 bc 0.84 ± 0.06 a 0.68 ± 0.03 b 0.003 0.097 0.005 0.096
      C/N 11.92 ± 0.57 b 10.24 ± 1.03 c 13.55 ± 0.58 a 12.84 ± 0.37 ab 12.15 ± 0.77 b 0.001 < 0.001 < 0.001 0.865
      C/P 29.30 ± 0.57 b 19.07 ± 1.03 d 36.62 ± 0.58 a 25.84 ± 0.37 bc 21.10 ± 0.77 cd < 0.001 0.088 < 0.001 0.743
      Biological characters
      ALP (nmol·(g·h)–1) 378.24 ± 39.48 c 386.23 ± 44.22 c 630.63 ± 41.25 a 658.85 ± 65.02 a 543.96 ± 62.02 b 0.334 < 0.001 < 0.001 0.814
      ACP (nmol·(g·h)–1) 1713.06 ± 168.92 b 1011.64 ± 219.72 c 2456.53 ± 99.30 a 2543.47 ± 23.69 a 2384.93 ± 41.21 a 0.062 < 0.001 < 0.001 0.975
      Data are means ± SD (n = 8). Values followed by different letters within a column indicate significant differences based on one-way ANOVA (p < 0.05). SWC, soil water content; AN, available nitrogen; SOM, soil organic matter; TC, total carbon; TN, total nitrogen; TP, total phosphorus; C/N, total carbon to total nitrogen ratio; C/P, total carbon to total phosphorus ratio; ALP, alkaline phosphatase; ACP, acid phosphatase. BM, bulk soil in mixed plantations; BP, bulk soil in monocultures; RMC, rhizosphere soil of Cunninghamia lanceolata in mixed plantations; RMP, rhizosphere soil of Phoebe bournei in mixed plantations; RPC, rhizosphere soil of Cunninghamia lanceolata in monocultures. Bold values denote significant differences (p < 0.05).

      Table 1. 

      Soil P fractions, physicochemical properties, and enzyme activities in bulk soil and rhizosphere soil.