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The effects of low levels of nitrogen deposition and grazing on dune grassland

Plassmann, Katharina; Edwards-Jones, Gareth; Jones, M. Laurence M.. 2009 The effects of low levels of nitrogen deposition and grazing on dune grassland. Science of the Total Environment, 407 (4). 1391-1404. 10.1016/j.scitotenv.2008.10.012

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Abstract/Summary

Coastal sand dunes are considered to be threatened by the atmospheric deposition of nitrogen (N); however, experimental investigations of the effects of N deposition on dune vegetation and soil using realistic N loads and sites with low background deposition are scarce. This study reports the effects of low levels of fertilisation with N and phosphorus (P) on the vegetation, above-ground biomass, plant tissue chemistry and soil chemistry of fixed dune grasslands. In addition, the impacts of grazing management and its potential to mitigate adverse effects of N fertilisation were examined. Four N treatments (unwatered control, watered control, + 7.5 kg ha− 1 year− 1, + 15 kg ha− 1 year− 1) were combined with three grazing treatments (ungrazed, rabbit grazed, rabbit and pony grazed). In a separate experiment, effects of fertilisation with both N (15 kg ha− 1 year− 1) and P (20 kg ha− 1 year− 1) were investigated. Vegetation composition was assessed using the point quadrat method. Above-ground biomass, sward heights, tissue N and P concentrations and soil chemical parameters were also measured. After two years, N addition resulted in greater amounts of total above-ground biomass, bryophyte biomass and changes in bryophyte tissue chemistry. No effects on vegetation composition, sward height or soil parameters occurred. Fertilisation with both nutrients had a greater impact on above-ground biomass, sward heights and sward structure than N addition alone. The grazing treatments differed in their species composition. The changes observed after only two years of fertilisation may lead to community changes over longer time scales. Effects were observed even under heavy grazing with phosphorus limitation. Therefore, the upper critical load for N for dune grasslands may be below the previously proposed 20 kg ha− 1 year− 1 and grazing may not mitigate all negative effects of N deposition.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.scitotenv.2008.10.012
Programmes: CEH Programmes pre-2009 publications > Biodiversity > BD01 Conservation and Restoration of Biodiversity
CEH Programmes pre-2009 publications > Biogeochemistry > BG02 Recovery from acidification and eutrophication
CEH Sections: Emmett
ISSN: 0048-9697
Additional Keywords: Critical load, Phosphorus, Grazing exclusion, Above-ground biomass, Mosses, Rabbits
NORA Subject Terms: Botany
Ecology and Environment
Date made live: 17 Feb 2009 12:41
URI: http://nora.nerc.ac.uk/id/eprint/4831

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