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Microbial immobilization and mineralization of dissolved organic nitrogen from forest floors |
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| Authors: | Bettina HM Schmidt Sabine Braun William H McDowell |
| Institution: | a Department of Soil Ecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95448 Bayreuth, Germany b Earth Surface Science, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands c Institute of Soil Ecology, Helmholtz Zentrum München, 85764 Neuherberg, Germany d Institute of Agricultural Climate Research, Johann Heinrich von Thünen Institute, 38116 Braunschweig, Germany e Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH 03824, USA |
| Abstract: | Dissolved organic nitrogen (DON) plays a key role in the N cycle of many ecosystems, as DON availability and biodegradation are important for plant growth, microbial metabolism and N transport in soils. However, biodegradation of DON (defined as the sum of mineralization and microbial immobilization) is only poorly understood. In laboratory incubations, biodegradation of DON and dissolved organic carbon (DOC) from Oi and Oa horizons of spruce, beech and cypress forests ranged from 6 to 72%. Biodegradation of DON and DOC was similar in most samples, and mineralization of DON was more important than microbial immobilization. Nitrate additions (0-10 mg N L−1) never influenced either DON immobilization by microorganisms or mineralization. We conclude that soil microorganisms do not necessarily prefer mineral N over DON for meeting their N demand, and that biodegradation of DON seems to be driven by the microbial demand for C rather than N. Quantifying the dynamics of DON in soils should include consideration of both C and N demands by microbes. |
| Keywords: | Dissolved organic nitrogen Dissolved organic carbon Nitrate Biodegradation Mineralization Microbial immobilization |
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