Figure 4.

Structural equation model visualizing pathways among multiple controlling factors over tropical forest diversity and vegetation C storage (represented by the first two axes of principal components analyses, PC1: climatic controls, PC2: edaphic controls). Arrows indicate significant positive (green) or negative (red) relationships among variables. Arrow width indicates effect strength, and numbers are significant standardized path coefficients. The overall goodness of fit of the model was assessed by the difference between the model and the data, based on Fisher’s C statistic that follows a chi-square distribution (Fisher C = 17.47; df = 20; p = 0.622). Akaike’s information criterion (AIC) was used to compare alternative models and determine the most parsimonious model presented here (AIC = 67.47). The coefficient of determination R2 and intra-class correlation coefficient from generalized linear mixed-effects models can be indicated by pseudo-R2 values⁸¹. For mixed models, marginal R2 considers only the variance captured by the fixed effects (DIV = 0.52; ACD = 0.66), and conditional R2 by both the fixed and random effects combined (DIV = 0.94; ACD = 0.96).