Future stratospheric ozone depletion will affect a subarctic dwarf shrub ecosystem

Ulf Johanson

Research output: ThesisDoctoral Thesis (compilation)

Abstract

The stratospheric ozone depletion and the concomitant increase in ultraviolet-B (UV-B, 280-320 nm) radiation is of global concern due to the effects of UV-B on living organisms. To investigate the effects of increased levels of UV-B, a field irradiation system was established at a subarctic dwarf shrub heath in Northern Sweden (68 °N). An ozone depletion of 15 % under clear sky conditions was simulated over a naturally growing ecosystem. The response of both individual components and processes was studied to reveal changes in ecosystem structure and function. Species with different life strategies (evergreen or deciduous) responded differently both in magnitude and direction. The evergreen species were more responsive to UV-B regarding shoot growth, which could be due to cumulative effects in long-lived tissues, since the retardation in relative growth increased over time of exposure. Leaves of evergreen species became thicker under enhanced UV-B, while leaves of deciduous species became thinner.

Decomposition studies (laboratory and in situ) showed that indirect effects of UV-B, due to changes in leaf tissue chemistry, affected microbial activity and slowed down the decomposition rate. More directly, UV-B decreased the abundance of some fungal species and hence the composition of species. However, no altered decomposition rate was found when decomposition progressed under high UV-B even if the microorganisms were fewer. This could be due to the increased direct photodegradation of litter that compensates for lower microbial activity. The decomposition rate is therefore strongly dependent on the interception of UV-B at the litter layer. This research has shown that ecosystem components and processes are affected in a number of ways and that there are indications of changes in species composition in a long-term perspective due to differences in responsiveness between the different species.
Original languageEnglish
QualificationDoctor
Awarding Institution
  • Department of Biology
Supervisors/Advisors
  • [unknown], [unknown], Supervisor, External person
Award date1997 Mar 22
Publisher
Print ISBNs91-628-2404-X
Publication statusPublished - 1997

Bibliographical note

Defence details

Date: 1997-03-22
Time: 10:15
Place: Department of Plant Physiology, Sölvegatan 35, Lund

External reviewer(s)

Name: Teramura, Alan H.
Title: Prof
Affiliation: College of Natural Science, University of Hawaii, Honolulu, USA

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The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Biology building (Closed 2011) (011008000)

Subject classification (UKÄ)

  • Biological Sciences

Keywords

  • Vaccinium
  • UVB
  • subarctic
  • shoot growth
  • ozone depletion
  • leaf thickness
  • irradiation system
  • heath ecosystem
  • Empetrum
  • dwarf shrubs
  • Calamagrostis
  • decomposition
  • Physiological biophysics
  • Växtfysiologi

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