New Paradigms of Nitrogen Mineralization and Availability.

N mineralization dynamics are modeled as a function of the quality and quantity of resource inputs and climate. However, just as the number of miles we can drive on a tank of gas also depends on internal engine properties, so, too, is N mineralization dependent on microbial decomposers, the engine driving soil biogeochemical processes. Decomposer community enzyme induction drives proteolysis, the exocellular first step in N mineralization. The structure and function of the community influences patterns of enzyme induction and thus rates of proteolysis. More, cellular carbon use efficiency and stoichiometry are internal processes driving ammonification. These microbial processes are strongly influenced by plant communities and their priming of the microbial population. All of these processes are further regulated by soil minerals, a strong sink for organic N but often ignored in N mineralization concepts. We use this and other emerging information to develop a new model of N mineralization, highlighting: proteolysis matters, is the rate limiting step and influenced by the size and structure (i.e. preferences and capabilities) of communities; minerals are a strong sink and source for bioavailable N; microbial community characteristics influence N mineralization via their growth efficiencies and stoichiometric properties; the various steps in N mineralization have different drivers and can become decoupled; and plants are a driving force in the cycle for their ability to prime mineral N, and influence the structure and function of microbial communities. Both chronic and abrupt environmental changes enhance this decoupling and hence unpredictability, creating a need to revisit and better understand the basic biological processes underpinning N mineralization.