Figure 7.

Structural Equation Model (SEM) showing the causal relationships among bacterial abundance, diversity, biomass, community composition, and copper concentrations in the fluvo-aquic soil (A) and red soil (B). The final model fits the data well (A): maximum likelihood, χ² = 2.604, df = 4, P = 0.626; goodness-of-fit index (GFI) = 0.984; Akaike Information Criteria (AIC) = 24.60; root square mean errors of approximation (RMSEA) = 0.000. (B): maximum likelihood, χ² = 0.878, df = 4, P = 0.928; goodness-of-fit index (GFI) = 0.994; Akaike Information Criteria (AIC) = 22.88; root square mean errors of approximation (RMSEA) = 0.000. Red and green lines indicate positive and negative pathways, respectively. Width of the line indicates the strength of the relationships. Standardized total effects (direct and indirect effects) were derived from the structural equation modeling (C,D). ^*P < 0.05, ^**P < 0.01, ^***P < 0.001.