Effects of increased deposition of atmospheric nitrogen on an upland Calluna moor: N and P transformations

M. G. Pilkington, S. J. M. caporn, J. A. Carroll, N. Cresswell, J. A. Lee, B. A. Emmett, David Johnson

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Abstract

This study determined the effects of increased N deposition on rates of N and P transformations in an upland moor. The litter layer and the surface of the organic Oh horizon were taken from plots that had received long-term additions of ammonium nitrate at rates of 40, 80 and 120 kg N ha(-1) yr(-1). Net mineralisation processes were measured in both field and laboratory incubations. Soil phosphomonoesterase (PME) activity and rates of N2O release were measured in laboratory incubations and root-surface PME activity measured in laboratory microcosms using Calluna vulgaris bioassay seedlings. Net mineralisation rates were relatively slow, with net ammonification consistently stimulated by N addition. Net nitrification was marginally stimulated by N addition in the laboratory incubation. N additions also increased soil and root-surface (PME) activity and rates of N2O release. Linear correlations were found between litter C:N ratio and all the above processes except net nitrification in field incubations. When compared with data from a survey of European forest sites, values of litter C:N ratio were greater than a threshold below which substantial, N input-related increases in net nitrification rates occurred. The maintenance of high C:N ratios with negligible rates of net nitrification was associated with the common presence of ericaceous litter and a mor humus layer in both this moorland as well as the forest sites. (c) 2005 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)469-480
Number of pages11
JournalEnvironmental Pollution
Volume135
Issue number3
DOIs
Publication statusPublished - 2005

Keywords

  • upland moor
  • mineralisation
  • phosphomonoesterase
  • dissolved organic nitrogen
  • N2O release
  • SOIL SOLUTION CHEMISTRY
  • ORGANIC-MATTER
  • NUTRIENT AVAILABILITY
  • HEATHLAND ECOSYSTEMS
  • ACID-PHOSPHATASE
  • FOREST SOILS
  • MINERALIZATION
  • DECOMPOSITION
  • GRADIENT
  • PLANT

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