Fig. 2.

Structural equation models representing direct and indirect linkages of environmental factors on VOC emission. (A) The conceptual model tested, in which temperature and soil moisture affect VOC emissions directly or indirectly by structuring the vegetation cover. (B) An example of a final SEM model for isoprene emission. Solid arrows represent significant linear paths supported by the model; dashed lines are omitted paths. Values represent standardized effect sizes. (C) Effect sizes on each VOC group summed across the SEM models for temperature and soil moisture, respectively. Direct effect sizes (green) correspond to parameter estimates between VOC and the given parameter. Indirect effects (purple) correspond to the mediated effect of a variable via the vegetation cover PC axis. All numbers are scaled to z-scores in order to enable comparisons of effect sizes across variable types. All deviations from 0 are significant.