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 .