Both ingrowth treatments and fertilization affect litter C and N
transformations, but there was no interaction between these factors.
Root ingrowth core treatments and fertilization treatments both altered
litter C and N transfers between SOM pools, but the root effect did not
depend on fertilization (SI Table 2, all p-values for ingrowth core
treatment x fertilization treatment interactions are above 0.05). As
such, subsequent data shown for each factor are aggregated over the
other factor.