Figure 2.

A, Piecewise structural equation models describing [CO₂] effects on R_Bio via changes in plant and fungal traits. B, Model results for T. ceratophorum indicate that both direct and indirect effects of [CO₂] on plant traits contributed to shifts in R_Bio. C, Model results for T. officinale indicate that primarily direct effects of [CO₂] on plant traits contributed to shifts in R_Bio. In B and C, boxes represent measured traits and solid arrows indicate significant pathways in the model (P < 0.05). Black and red arrows indicate positive and negative correlations, respectively. The thickness of solid arrows was scaled to reflect the magnitude of the standardized regression coefficients. r² values for each component model and standardized pathway coefficients are listed in Supplemental Table S4.