Root production
In contrast to the patterns observed with root-derived C inputs, root production was strongly predicted by site and (to a lesser extent) ECM dominance, with a significant site × ECM dominance interaction (R2 = 0.72, P < 0.001). Comparing the end-member plots only, root production varied significantly both by plot mycorrhizal type (F1,24= 4.66, P = 0.041) and among sites (F5,24 = 15.19, P < 0.001; Fig. 2b). Overall, root production was greater in ECM-dominated plots compared to AM-dominated plots. The highest root production was observed in ECM plots at HF (107 ± 8.94 g C m-2 yr-1) while the lowest root production was observed in ECM plots at SCBI (16.4 ± 1.13 g C m-2 yr-1). While there were no significant pairwise differences between plot mycorrhizal types within a given site, mean root production values were higher in ECM compared to AM plots at four of the six sites: HF, LDW, SERC, and TRC.