2-4. Soil analysis
Soil samples taken from depths of 5–10 cm at the three plots within the Hyakumakidani watershed were mixed to produce composite samples for analyzing carbon and nitrogen contents. After taking a moderate amount of air-dried soil and measuring its mass, carbon and nitrogen were measured using a CN coder to determine the C/N ratio of the soil.
2-5. Measuring thenet nitrification rate and net nitrogen mineralization rate
The net nitrification rate and net nitrogen mineralization rate were measured at 3, 15, and 30℃, using the composite samples according to Honoki et al. (Honoki et al., 2001). The increase in nitrate before and after incubation was defined as net nitrification , and the increase in nitrate plus the increase in ammonium was defined asnet nitrogen mineralization .