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Effects of enhanced ultraviolet-B radiation on subarctic ecosystems

Gehrke, Carola LU (1998)
Abstract (Swedish)
Popular Abstract in Swedish

I takt med att den stratosferiska ozonskikten tunnas ut når mera av solens skadliga ultraviolet-B strålning (UV-B, 280 - 320 nm) jordytan. I avhandlingen beskrivs det effekter av ökad UV-B strålning på komponenter (mossor) och processer (nedbrytning av förna, biomassa produktion, arternas samspel) i ekosystem på höga breddgrader. Experiment utfördes där en hed och en myr i norra Sverige (Abisko) utsattes för förhöjd UV-B strålning under två till fyra växtsäsonger. Den förhöjda UV-B strålningen motsvarade vad som förväntas när ozonskiktet tunnas ut med 15%. Bland mossorna undersöktes vitmossa, (Sphagnum fuscum), husmossa (Hylocomium splendens) och björnmossa (Polytrichum commune). Ökad UV-B... (More)
Popular Abstract in Swedish

I takt med att den stratosferiska ozonskikten tunnas ut når mera av solens skadliga ultraviolet-B strålning (UV-B, 280 - 320 nm) jordytan. I avhandlingen beskrivs det effekter av ökad UV-B strålning på komponenter (mossor) och processer (nedbrytning av förna, biomassa produktion, arternas samspel) i ekosystem på höga breddgrader. Experiment utfördes där en hed och en myr i norra Sverige (Abisko) utsattes för förhöjd UV-B strålning under två till fyra växtsäsonger. Den förhöjda UV-B strålningen motsvarade vad som förväntas när ozonskiktet tunnas ut med 15%. Bland mossorna undersöktes vitmossa, (Sphagnum fuscum), husmossa (Hylocomium splendens) och björnmossa (Polytrichum commune). Ökad UV-B strålning minskade mossornas längdtillväxt och förändrade skottens morfologi. Arterna var olika känsligt för ökad UV-B strålning. Det kan förändra arternas konkurrensförmåga och artsammansättningen. Så var ännu inte fallet i hedekosystemet för lavar, mossor och kärlväxter efter fyra år under förhöjd UV-B strålning. Biomassa produktionen var oförändrad för vitmossan som dominerade myrekosystemet. För husmossan i hedekosystemet däremot minskade biomassa produktionen med en tredjedel. Nedbrytning av blåbär och odon förna skedde långsammare om bladen hade vuxit under förhöjd UV-B strålning. Det orsakades av en ändring i den kemiska blad kvaliten då UV-B strålning ökade halten av svårt nedbrytbara ämnen. (Less)
Abstract
Biologically harmful ultraviolet-B radiation (UV-B, 280-320 nm) is increasing at the Earth´s surface owing to stratospheric ozone depletion. This is of global concern due to potential impacts of enhanced UV-B radiation on the biosphere. The aim of this thesis was to investigate effects of enhanced UV-B radiation on components (bryophytes) and processes (decomposition, productivity, species interactions) in ecosystems. In the Subarctic, a bog and a birch-heath ecosystem were exposed to enhanced UV-B radiation for two and three growing seasons, respectively. A 15% ozone depletion was simulated. Bryophytes (Sphagnum fuscum, Hylocomium splendens, Polytrichum commune), representing different morphological ?types? and growth strategies,... (More)
Biologically harmful ultraviolet-B radiation (UV-B, 280-320 nm) is increasing at the Earth´s surface owing to stratospheric ozone depletion. This is of global concern due to potential impacts of enhanced UV-B radiation on the biosphere. The aim of this thesis was to investigate effects of enhanced UV-B radiation on components (bryophytes) and processes (decomposition, productivity, species interactions) in ecosystems. In the Subarctic, a bog and a birch-heath ecosystem were exposed to enhanced UV-B radiation for two and three growing seasons, respectively. A 15% ozone depletion was simulated. Bryophytes (Sphagnum fuscum, Hylocomium splendens, Polytrichum commune), representing different morphological ?types? and growth strategies, responded to UV-B enhancement with altered shoot morphology and reduced stem increment. Changed growth was not clearly linked to alterations in pigmentation, maximum net photosynthesis or dark respiration. Feedbacks of growth alterations on intra- and interspecific interactions are discussed. Productivity per unit area was not affected in S. fuscum. The main variables determining productivity (length increment, shoot mass relations, spatial shoot density) were affected although in opposite directions. UV-B-induced changes in shoot biometry and reduced spatial shoot density imply long-term effects on peat structure with possible feedback on productivity and decomposition. In H. splendens, enhanced UV-B radiation reduced current year´s shoot biomass production by 25% and tended to decrease spatial shoot density. The effect on these variables caused an amplified effect at the community level as productivity per unit area was reduced by 34%. Decomposition studies were done with dwarf shrub litter in the laboratory and in the heath. Altered leaf litter quality, which was induced during leaf growth under enhanced UV-B radiation, caused a decrease in microbial decomposer activity and delayed litter turnover. UV-B radiation applied during decomposition reduced microbial decomposer activity and decreased the abundance of fungi in the decomposer community but did not delay litter turnover. The potential delay was possibly offset by photodegradation of litter. Changes in species composition in the heath (including phanerogams and cryptogams) were not detectable after four growing seasons. Because of differences in UV-B responsiveness between species with different growth strategies, a shift in species composition could occur over the long-term perspective. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • prof Caldwell, Martyn M., Utah, U.S.A.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
pigmentation, photosynthesis, dark respiration, shoot morphology, shoot growth, phanerogams), species composition (cryptogams, productivity, decomposition, dwarf shrubs, bryophytes, peatland ecosystem, heath ecosystem, UV-B, ozone depletion, Plant ecology, Växtekologi
pages
110 pages
publisher
Plant Ecology, Ecology Building, SE-223 62 Lund
defense location
Ecology building, Sölvegatan 37, Lund
defense date
1998-05-20 10:15
external identifiers
  • Other:ISRN: SE-LUNDS/NBBE-98/1049/+110pp
ISBN
ISBN 91-7105-101-5
language
English
LU publication?
yes
id
9d0b2218-4121-4b99-a713-92261d647df8 (old id 38621)
date added to LUP
2007-07-31 09:03:58
date last changed
2016-09-19 08:45:11
@phdthesis{9d0b2218-4121-4b99-a713-92261d647df8,
  abstract     = {Biologically harmful ultraviolet-B radiation (UV-B, 280-320 nm) is increasing at the Earth´s surface owing to stratospheric ozone depletion. This is of global concern due to potential impacts of enhanced UV-B radiation on the biosphere. The aim of this thesis was to investigate effects of enhanced UV-B radiation on components (bryophytes) and processes (decomposition, productivity, species interactions) in ecosystems. In the Subarctic, a bog and a birch-heath ecosystem were exposed to enhanced UV-B radiation for two and three growing seasons, respectively. A 15% ozone depletion was simulated. Bryophytes (Sphagnum fuscum, Hylocomium splendens, Polytrichum commune), representing different morphological ?types? and growth strategies, responded to UV-B enhancement with altered shoot morphology and reduced stem increment. Changed growth was not clearly linked to alterations in pigmentation, maximum net photosynthesis or dark respiration. Feedbacks of growth alterations on intra- and interspecific interactions are discussed. Productivity per unit area was not affected in S. fuscum. The main variables determining productivity (length increment, shoot mass relations, spatial shoot density) were affected although in opposite directions. UV-B-induced changes in shoot biometry and reduced spatial shoot density imply long-term effects on peat structure with possible feedback on productivity and decomposition. In H. splendens, enhanced UV-B radiation reduced current year´s shoot biomass production by 25% and tended to decrease spatial shoot density. The effect on these variables caused an amplified effect at the community level as productivity per unit area was reduced by 34%. Decomposition studies were done with dwarf shrub litter in the laboratory and in the heath. Altered leaf litter quality, which was induced during leaf growth under enhanced UV-B radiation, caused a decrease in microbial decomposer activity and delayed litter turnover. UV-B radiation applied during decomposition reduced microbial decomposer activity and decreased the abundance of fungi in the decomposer community but did not delay litter turnover. The potential delay was possibly offset by photodegradation of litter. Changes in species composition in the heath (including phanerogams and cryptogams) were not detectable after four growing seasons. Because of differences in UV-B responsiveness between species with different growth strategies, a shift in species composition could occur over the long-term perspective.},
  author       = {Gehrke, Carola},
  isbn         = {ISBN 91-7105-101-5},
  keyword      = {pigmentation,photosynthesis,dark respiration,shoot morphology,shoot growth,phanerogams),species composition (cryptogams,productivity,decomposition,dwarf shrubs,bryophytes,peatland ecosystem,heath ecosystem,UV-B,ozone depletion,Plant ecology,Växtekologi},
  language     = {eng},
  pages        = {110},
  publisher    = {Plant Ecology, Ecology Building, SE-223 62 Lund},
  school       = {Lund University},
  title        = {Effects of enhanced ultraviolet-B radiation on subarctic ecosystems},
  year         = {1998},
}