, Volume 88, Issue 2, pp 189–196

Nitrogen mineralization, nitrification and denitrification in upland and wetland ecosystems

  • Donald R. Zak
  • David F. Grigal
Original Papers

DOI: 10.1007/BF00320810

Cite this article as:
Zak, D.R. & Grigal, D.F. Oecologia (1991) 88: 189. doi:10.1007/BF00320810


Nitrogen mineralization, nitrification, denitrification, and microbial biomass were evaluated in four representative ecosystems in east-central Minnesota. The study ecosystems included: old field, swamp forest, savanna, and upland pin oak forest. Due to a high regional water table and permeable soils, the upland and wetland ecosystems were separated by relatively short distances (2 to 5 m). Two randomly selected sites within each ecosystem were sampled for an entire growing season. Soil samples were collected at 5-week intervals to determine rates of N cycling processes and changes in microbial biomass. Mean daily N mineralization rates during five-week in situ soil incubations were significantly different among sampling dates and ecosystems. The highest annual rates were measured in the upland pin oak ecosystem (8.6 g N m−2 yr−1), and the lowest rates in the swamp forest (1.5 g N m−2 yr−1); nitrification followed an identical pattern. Denitrification was relatively high in the swamp forest during early spring (8040 μg N2O−N m−2 d−1) and late autumn (2525 μg N2O−N m−2 d−1); nitrification occurred at rates sufficient to sustain these losses. In the well-drained uplands, rates of denitrification were generally lower and equivalent to rates of atmospheric N inputs. Microbial C and N were consistently higher in the swamp forest than in the other ecosystems; both were positively correlated with average daily rates of N mineralization. In the subtle landscape of east-central Minnesota, rates of N cycling can differ by an order of magnitude across relatively short distances.

Key words

N mineralization Nitrification Microbial biomass Denitrification Spatial variability 

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Donald R. Zak
    • 1
    • 2
  • David F. Grigal
    • 2
  1. 1.Department of Soil ScienceUniversity of MinnesotaSt. PaulUSA
  2. 2.Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulUSA
  3. 3.School of Natural ResourcesUniversity of MichiganAnn ArborUSA

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