Cedar Creek Natural History Area: Literature   Up   Home


Citation. Zak, D. R.; Grigal, D. F. 1991. Nitrogen mineralization, nitrification and denitrification in upland and wetland ecosystems. Oecologia 88:189-196.   [1218  LTER]

Summary. 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-l); nitrification followed an identical pattern. Denitrification was relatively high ill the swamp forest during early spring (8040 micrograms N2O-N m-2 d-1) and late autumn (2525 micrograms 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.

Keywords. N mineralization, Nitrification, Microbial biomass, Denitrification, Spatial variability

For reprints or technical issues, please correspond with the author of the paper. For comments on the format or contents of the web site, please contact webmaster@cedarcreek.umn.edu