Soil fractionation
Ingrowth cores were destructively harvested in September and litter C and N inputs were traced into SOM pools (Ridgeway et al., 2022). A 5 g subsample of dry soil from each core was separated into light POM, heavy POM, and MAOM by density and size fractionation as described in Lavallee et al. (2020). In brief, the light POM was separated through density floatation in 1.85 g/mL sodium polytungstate salt solution. The remaining soil was separated into heavy POM and MAOM fractions by size separation where the MAOM fraction passes through a 53 um sieve.