Effects of enhanced ultraviolet-B radiation on subarctic ecosystems

• Main Author: Gehrke, Carola
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Plant Ecology, Ecology Building, SE-223 62 Lund 1998
• Subjects: Ecology; 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; Subarctic
• Online Access: https://lup.lub.lu.se/record/38621

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 ...