A nitrogen mineralization model based on relationships for gross mineralization and immobilization

Net N mineralization from plant materials represents the difference between the two opposing processes of gross N mineralization and immobilization. This complicates the derivation of useful relationships between rates of net mineralization and litter quality indices. The purpose of the current paper is to present a model for net N mineralization from plant material that is based on relationships between (1) gross N mineralization and respiration and (2) gross N immobilization and respiration found in studies applying 15N dilution techniques. Together these relationships produce an overall relationship between net N mineralization and C mineralization that can be used to predict net N mineralization from respiration. The applicability of the model was tested by applying it to the mineralization dynamics of 75 plant materials with widely differing qualities. In a model validation on eight independent plant materials, the relations between net N mineralization and C mineralization resulted in good predictions of observed net N mineralization patterns from the C mineralization pattern, depending only on the C/N ratio of the plant material (R2=0.90R2=0.90). This suggests that the relationship between net N mineralization and respiration is largely unaffected by the chemical composition of the plant material other than the C/N ratio. This means that the chemical composition of the plant material may primarily influence N mineralization through its effect on C mineralization. Furthermore, the relationship between net N mineralization and C mineralization is useful for predictions of net N mineralization because C mineralization is generally much easier to predict than net N mineralization.