Fig. 6: Structural equation models (SEMs) for ecosystems and climatic zones.
a Subtropical grassland. b Temperate grassland. c Subtropical forest. d Temperate forest. The SEMs show the causality and correlation between the absolute content of soil amino sugars (characterization of microbial residues) and environmental variables. Red lines indicate positive effects, while blue lines indicate negative effects. The thickness and color of the line are directly proportional to the standardized path coefficient on the single arrow. SOC soil organic carbon. R2 represents the variance of biomarkers explained by the model. The asterisk (*) indicates the significance of the path; one, two, and three asterisks indicate p < 0.05, p < 0.01, and p < 0.001, respectively.
