Fig. 6. The active organic N pool as affected by treatment, incubation time, and the equation used for estimation. Estimates on or after the symbols marked with arrows were based on AL (labeled NH⁺₄–N) and Q_e (¹⁵N abundance of a N pool at the time of sampling during incubation) of the NH⁺₄ pool. Treatments are as follows: Treatment 1, 10 mg labeled NH⁺₄–N kg^-1; Treatment 2, 10 mg labeled NH⁺₄–N + 1000 mg C kg^-1; and Treatment 3, 100 mg labeled NH⁺₄–N + 1000 mg C kg^-1. The vertical bars represent ±SD.