, Volume 96, Issue 2, pp 186–192

Nitrogen mineralization dynamics in grass monocultures

  • David A. Wedin
  • John Pastor
Original Papers


Although Wedin and Tilman (1990) observed large differences in in situ N mineralization among monocultures of five grass species, the mechanisms responsible were unclear. In this study, we found that the species did not change total soil C or N, and soil C: N ratio (range 12.9–14.1) was only slightly, but significantly, changed after four years. Nor did the species significantly affect the total amount of N mineralized (per g soil N) in year-long aerobic laboratory incubations. However, short-term N mineralization rates in the incubations (day 1–day 17) differed significantly among species and were significantly correlated with annual in situ mineralization. When pool sizes and turnover rates of potentially mineralizable N (No) were estimated, the best model treated No as two pools: a labile pool, which differed among species in size (Nl, range 2–3% of total N) and rate constant (h, range 0.04–0.26 wk−1), and a larger recalcitrant pool with a constant mineralization rate across species. The rate constant of the labile pool (h) was highly correlated with annual in situ N mineralization (+0.96). Therefore, plant species need only change the dynamics of a small fraction of soil organic matter, in this case estimated to be less than 3%, to have large effects on overall system N dynamics.

Key words

N mineralization Monocultures Soil organic matter Grasses 


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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • David A. Wedin
    • 1
  • John Pastor
    • 1
  1. 1.Natural Resources Research InstituteUniversity of MinnesotaDuluthUSA
  2. 2.Department of BotanyUniversity of TorontoTorontoCanada

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