Nitrogen Mineralization: Challenges of a Changing Paradigm

Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, United States
Ecology (Impact Factor: 4.66). 03/2004; 85(3):591–602. DOI: 10.1890/03-8002


Until recently, the common view of the terrestrial nitrogen cycle had been driven by two core assumptions—plants use only inorganic N and they compete poorly against soil microbes for N. Thus, plants were thought to use N that microbes ‘‘left over,’’ allowing the N cycle to be divided cleanly into two pieces—the microbial decomposition side and the plant uptake and use side. These were linked by the process of net mineralization. Over the last decade, research has changed these views. N cycling is now seen as being driven by the depolymerization of N-containing polymers by microbial (including mycorrhizal) extracellular enzymes. This releases organic N-containing monomers that may be used by either plants or microbes. However, a complete new conceptual model of the soil N cycle needs to incorporate recent research on plant–microbe competition and microsite processes to explain the dynamics of N across the wide range of N availability found in terrestrial ecosystems. We discuss the evolution of thinking about the soil N cycle, propose a new integrated conceptual model that explains how N cycling changes as ecosystem N availability changes, and discuss methodological issues raised by the changing paradigm of terrestrial N cycling.

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Available from: Joshua P Schimel
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    • "Our conclusions are predicated on extracellular enzymes acting as the proximate agents of decomposition in soils (Schimel & Weintraub, 2003;Schimel & Bennett, 2004) and therefore providing strong proxies of soil biogeochemical functioning. Soil enzymes, decomposition rates, and respiration rates are often strongly correlated (Frankenberger & Dick, 1983;Sinsabaugh et al., 1993;Waring, 2013). "
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    • "Nitrate leaching represents a resource loss and can threaten drinking water quality. Nitrate concentrations in soil solution and nitrate leaching depend on the relation between uptake by plants and soil organisms, atmospheric N 2 fixation, N mineralization (ammonification and nitrification), N deposition from the atmosphere, denitrification, and volatilization (Corre et al., 2002; Schimel and Bennett, 2004). Leaching of nitrate from soil is mainly driven by land-use type, management (e.g., fertilization), land-use change, climate, and soil properties (Dijkstra et al., 2007; Lilburne and Webb, 2002; Perego et al., 2012; Schilling and Spooner, 2006; Strebel et al., 1989). "
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    No preview · Article · Dec 2015 · Agriculture Ecosystems & Environment
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    • "Subsequently , it became more widely known that the plants also take up organic N (N€ asholm et al., 1998, 2009) and that various forms of organic N may dominate N uptake in ecosystems with a low soil N supply (Schimel and Bennett, 2004). The occurrence of inorganic N could be viewed as a supply of organic N in excess of the current biological demands of ecosystems (Schimel and Bennett, 2004), which is also dependent on the supply of carbon to the organisms (Hart et al., 1994a). Like peptides and amino acids, inorganic forms of N are rapidly taken up when the supply is low, and may, therefore not be detected when their pool sizes are measured. "
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