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Critical loads of nitrogen deposition and changes in vegetation diversity - the protection of swedish wetlands in a long-term perspective
2002 (English)Independent thesis Basic level (degree of Bachelor)Student thesis
Abstract [en]

The Swedish Landscape is covered with about 9.3 million hectares wetland. Wetlands are important ecosystems with high species diversity and special ecological circumstances, but are threatened in many ways. Usually poor in nutrients, wetlands suffer not only from acidification, but also from air-borne nitrogen deposition. Since it became visible that air-pollutants can be transported over long distances in the air and have harmful effects on different ecosystems, an international agreement to reduce emissions of several pollutants was adopted and came into force in 1983. The Convention on Long-Range Transboundary Air-Pollution (CLRTAP) and its several protocols contain emission ceilings, and since the second sulphur protocol critical loads were determined. Thus, emission ceilings on the basis of their effects on ecosystems were established, different for each party. In this study it is investigated, if the diversity of Swedish wetlands is affected by air-borne nitrogen in a long-term perspective and if the critical loads, which were established by the CLRTAP for wetlands (for mesotrophic fens: 20-35 kg N ha/yr; for ombrotrophic bogs and Shallow soft-water bodies: 5-10 kg N ha/yr), are sufficient to protect these sensitive ecosystems. For this reason, four different studies were selected and reviewed. Three studies contain changes in vegetation composition on Swedish wetlands in southern and central Sweden. The areas were reinvestigated after long periods (40-50 years). Another study describes the effects of growth and interspecific competition in Sphagnum after temperature, nitrogen and sulphur treatments in a field experiment on a mire in northern Sweden. The results of these studies are described and compared to data, containing the total nitrogen deposition during a period of more or less ten years (from 1988/89 until 2000), measured in the near of each investigated areas. Comparing the results of the reviewed studies with the amounts of nitrogen deposition, a connection between changes in diversity and the nitrogen influx is visible. The mean-values of nitrogen deposition for four selected monitoring stations were 8 kg/ha/yr (1988-2000) for southern Sweden, 4 kg/ha/yr (1993-2000) and 7 kg/ha/yr (1991-2000) for central Sweden and 5 kg/ha/yr (1991-2000) for the northern part of Sweden. Because all mean-values are lying in between the lowest critical load of 5-10 kg/ha/yr, this might indicate that the critical loads are not sufficient to protect Swedish wetlands in a long-term perspective. A critical load of nitrogen deposition somewhere below 5 kg/ha/yr might be necessary and further research with long-term studies and field experiments with lower nitrogen influxes are needed.

Place, publisher, year, edition, pages
2002. , 19 p.
Identifiers
URN: urn:nbn:se:kau:diva-54441Local ID: MIV C-2OAI: oai:DiVA.org:kau-54441DiVA: diva2:1103169
Subject / course
Environmental Science
Available from: 2017-05-30 Created: 2017-05-30

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
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Output format
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  • asciidoc
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