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 language | English |
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Pages (from-to) | 469-480 |
Number of pages | 11 |
Journal | Environmental Pollution |
Volume | 135 |
Issue number | 3 |
DOIs | |
Publication status | Published - 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