The effects of quantity and duration of simulated pollutant nitrogen deposition on root-surface phosphatase activities in calcareous and acid grasslands: a bioassay approach

D Johnson, J R Leake, J A Lee

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Abstract

A field and laboratory based bioassay has been developed to investigate the effects of the quantity and duration of simulated pollutant nitrogen (N) deposition on root-surface phosphomonoesterase (PME) activities in calcareous and acid grasslands. Seedlings of Plantago lanceolata were transplanted to a calcareous grassland and Agrostis capillaris seedlings were grown in microcosms containing soil from an acid grassland that had received either 7 yr (long-term) N additions or 18 months (short-term) N and phosphorus (P) additions. The bioassay revealed that short-term N treatments had little effect on the enzyme activity, whereas long-term N additions significantly increased PME activity within 7 d of transplanting into the field plots. Root-surface PME activity of A. capillaris was significantly reduced in soil that received additions of P. In the plots receiving long-term additions of N, a strong relationship was observed between extractable soil ammonium and root-surface PME activity. Soil ammonium concentrations accounted for 67% of the variation in PME activity of P. lanceolata in the calcareous grassland, and 86%, of the variation in PME activity of A. capillaris in the acid grassland. These results provide evidence that N deposition may have considerable effects on the demand and turnover of P in ecosystems that are approaching or have reached N saturation.

Original languageEnglish
Pages (from-to)433-442
Number of pages10
JournalNew Phytologist
Volume141
Issue number3
DOIs
Publication statusPublished - Mar 1999

Keywords

  • nitrogen deposition
  • phosphomonoesterase
  • nutrient cycling
  • organic phosphorus
  • ammonium
  • barley roots
  • phosphorus
  • soil
  • plants
  • saturation
  • growth

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