Nitrogen Mineralization and Immobilization: New Thoughts on Old Themes.

The previous 25 years of research on N mineralization and immobilization, much of it using ¹⁵N, has altered our conceptual understanding of these opposing processes. Some paradigm shifts include: a more central role for DON, including the microbially produced enzymes that are key to its formation; the role of soil fauna in turning over the soil microbial biomass and stimulating N mineralization; and the importance of soil heterogeneity in regulating NH₄⁺ production and consumption. We anticipate that the next refinement will likely be the incorporation of microbial community composition as a factor in N mineralization and immobilization processes.