| 1. |
- Cornelissen, Johannes H C, et al.
(author)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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In: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Journal article (peer-reviewed)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 2. |
- Moody, Sandra A., et al.
(author)
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The direct effects of UV-B radiation on Betula pubescens litter decomposing at four European field sites
- 2001
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In: Plant Ecology. - 1573-5052. ; 154:1-2, s. 27-36
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Journal article (peer-reviewed)abstract
- A co-ordinated series of field experiments were conducted to consider the effects of elevated UV-B radiation applied directly to decomposing plant litter. Betula pubescens was decomposed under ambient and elevated UV-B (simulating a 15% ozone depletion) using outdoor irradiation facilities at Adventdalen, Norway (78° N), Abisko, Sweden (68° N), Amsterdam, The Netherlands (52° N,) and Patras, Greece (38° N). There was no significant effect of treatment on mass loss for samples collected after 2, 12 and 14 months decomposition at Amsterdam, or after 4 months decomposition at Adventdalen. Significant reductions in the mass loss of litter decomposing under elevated UV-B compared to ambient were found at the other 2 sites. The only effect of treatment on litter chemistry during decomposition was a significant reduction in the N concentration of material at Abisko and a significant increase in C:N at Patras for litter decomposing under elevated UV-B. Significant differences were found in the structure of the fungal community decomposing litter in Sweden, the only site to be tested. These data, and the few published studies of the response of decomposition to UV-B incident on litter suggest that, in the ecosystems and climates that have been studied, such direct effects are typically confined to the initial stages of decomposition, and are rather small in magnitude.
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| 3. |
- Rozema, Jelte, et al.
(author)
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Paleoclimate: Toward solving the UV puzzle
- 2002
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 296:5573, s. 1621-1622
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Journal article (peer-reviewed)abstract
- Decreases in stratospheric ozone caused by chlorofluorocarbons released into the atmosphere lead to an increase in harmful ultraviolet (UV) light received at Earths surface. But UV and ozone also vary naturally as a result of changes in solar activity. In their Perspective, Rozema et al. chart recent efforts to elucidate the relation among the solar UV spectrum, ozone concentrations, and harmful surface UV on decadal and longer time scales. Biological proxies (phenolic compounds in pollen and spores) can be used to reconstruct historical UV-B and total ozone.
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| 4. |
- Rozema, Jelte, et al.
(author)
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Stratospheric ozone depletion: High arctic tundra plant growth on Svalbard is not affected by enhanced UV-B after 7 years of UV-B supplementation in the field
- 2006
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In: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 182:1-2, s. 121-135
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Journal article (peer-reviewed)abstract
- The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants.
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| 5. |
- Rozema, Jelte, et al.
(author)
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UV-B as an environmental factor in plant life: stress and regulation
- 1997
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In: Trends in Ecology & Evolution. - 1872-8383. ; 12:1, s. 22-28
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Journal article (peer-reviewed)abstract
- Recent studies indicate that increasing solar UV-B is not merely an environmental stress for plants. Solar UV-B can cause plant morphogenetic effects, which can, in turn, modify the architecture of plants and the structure of a vegetation, In addition, UV-B radiation affect the production of various secondary metabolites (such as flavonoids, tannins and lignin) with important physiological and ecological consequences.
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