## 2 Methods
### Extracellular Enzyme Activity and Specific Enzyme Activity Calculations  
A subset of each fresh, root-free, homogenized soil from each site, sampling location and horizon was frozen at \(-\)20 \({}^{\circ}\)C until enzyme analysis. Soils were analyzed for a suite of C-degrading enzymes: \(\alpha\)-glucosidase (AG; EC 3.2.1.20), \(\beta\)-glucosidase (BG; EC 3.2.1.21), xylosidase (XYL; EC 3.2.1.37), cellobiohydrolase (CBH; EC 3.2.1.91), phenol oxidase (POX; EC 1.10.3.2), and peroxidase (PER; EC 1.11.1.7). Soils were also analyzed for the N-degrading enzyme N-acetyl glucosamide (NAG; EC: 3.2.1.30). Substrates for all enzyme assays were dissolved in 50 mM, pH 5.0 acetate buffer solution.  
Hydrolytic enzymes (AG, BG, YXL, CBH, and NAG) were measured using techniques outlined in [PERSON] et al. [46]. Approximately 0.5 g dry weight of soil sample was suspended in 50 mL of a 50 mM, pH 5.0 acetate buffer solution and homogenized in a blender for 1 min. In a 2 mL centrifuge tube, 0.9 mL aliquot of the soil-buffer suspension was combined with 0.9 mL of the appropriate 5 mM p-nitrophenyl substrate solution for a total of three analytical replicates. Additionally, duplicate background controls consisted of 0.9 mL aliquot of soil-buffer suspension plus 0.9 mL of acetate buffer and four substrate controls were analyzed consisting of 0.9 mL substrate solution plus 0.9 mL buffer. The samples were agitated for 2-6 h at the treatment temperature. Samples were then centrifuged at 8160 g for 3 min. Supernatant (1.5 mL) was transferred to a 15 mL centrifuge tube containing 150 \(\mu\)L 1.0 M NaOH and 8.35 mL dH\({}_{2}\)O. The resulting mixture was vortexed and a subsample transferred to a cuvette and the optical density at 410 nm was measured on a spectrophotometer (Beckman Coulter DU 800 Spectrophotometer, Brea, CA, USA).  
Oxidative enzymes (POX and PER) were measured using techniques outlined in [PERSON] et al. [47]. POX and PER are primarily involved in oxidation of phenol compounds and depolymerization of lignin. The same general procedure for hydrolytic enzymes was followed utilizing a 5 mM L-3,4-Dihydroxyphenylalanine (L-DOPA) (Sigma-Aldrich Co. LLC, St. Louis, MO, USA) solution as the substrate. After set up of analytical replicates and substrate and background controls, the samples were agitated for 2-4 h at the treatment temperature. Samples were then centrifuged at 8160 g for 3 min. The resulting supernatant turns an intense indigo color. PER was determined similar to that of POX, except with the addition of 0.2 mL of 0.3% H\({}_{2}\)O\({}_{2}\) to all sample replicates and controls. Supernatant (1.4 mL) was transferred directly to a cuvette and the optical density at 460 nm was measured on the spectrophotometer.  
For all enzymes, the mean absorbance of two background controls and four substrate controls was subtracted from that of three analytical replicates and divided by the molar efficiency (1.66/mol), length of incubation (h), and soil dry weight. PER activity was determined by subtracting the absorbance for POX from the absorbance for PER. Enzyme activity at each measurement date was expressed as \(\mu\)mol substrate per unit SOC per hour (\(\mu\)mol g SOC \({}^{-1}\) h\({}^{-1}\)), per unit dry weight of soil and time (\(\mu\)mol g \({}^{-1}\) h\({}^{-1}\)), and per unit MBC and time (\(\mu\)mol g MBC \({}^{-1}\) h\({}^{-1}\)). The SOC pool size and MBC were measured in a previous study using the same soils and details on this analysis can be found in [PERSON] et al. [16].