A flexible model for quantitative comparisons of nitrogen mineralization patterns

Summary

Patterns of N mineralization vary widely between ecosystems, making intra- and interexperimental comparisons difficult at best. A flexible model, the Richards model, is suggested as a way of making comparisons. By changing its shape parameter, a flexible model can fit multiple mechanistic models, including first-order and logistic models. The scale-independent shape parameter (m) is a continuous variable that can be statistically analyzed to determine changes or differences in patterns. The model was tested with (1) simulations based on other mechanistic models; and with N mineralization data on soils from (2) urban and rural sites in New York; (3) forest soils in Alberta, Canada; and (4) arid and semiarid soils in Morocco. In all examples, the model was capable of fitting the data nearly as well as other specific models. With data based on the m values, soils in Morocco and organic horizons of coniferous forests in Alberta showed the same range in N mineralization patterns, although the soils varied in the amount of mineralizable N by an order of magnitude and time to reach maximum mineral N production by two-fold.