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- Tietjen, Britta, et al.
(författare)
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Climate change-induced vegetation shifts lead to more ecological droughts despite projected rainfall increases in many global temperate drylands
- 2017
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:7, s. 2743-2754
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Tidskriftsartikel (refereegranskat)abstract
- Drylands occur worldwide and are particularly vulnerable to climate change because dryland ecosystems depend directly on soil water availability that may become increasingly limited as temperatures rise. Climate change will both directly impact soil water availability and change plant biomass, with resulting indirect feedbacks on soil moisture. Thus, the net impact of direct and indirect climate change effects on soil moisture requires better understanding. We used the ecohydrological simulation model SOILWAT at sites from temperate dryland ecosystems around the globe to disentangle the contributions of direct climate change effects and of additional indirect, climate changeinduced changes in vegetation on soil water availability. We simulated current and future climate conditions projected by 16 GCMs under RCP 4.5 and RCP 8.5 for the end of the century. We determined shifts in water availability due to climate change alone and due to combined changes of climate and the growth form and biomass of vegetation. Vegetation change will mostly exacerbate low soil water availability in regions already expected to suffer from negative direct impacts of climate change (with the two RCP scenarios giving us qualitatively similar effects). By contrast, in regions that will likely experience increased water availability due to climate change alone, vegetation changes will counteract these increases due to increased water losses by interception. In only a small minority of locations, climate change-induced vegetation changes may lead to a net increase in water availability. These results suggest that changes in vegetation in response to climate change may exacerbate drought conditions and may dampen the effects of increased precipitation, that is, leading to more ecological droughts despite higher precipitation in some regions. Our results underscore the value of considering indirect effects of climate change on vegetation when assessing future soil moisture conditions in water-limited ecosystems.
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- Wan, Chi-Wai, et al.
(författare)
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Anthracene-BODIPY Cassettes: Syntheses and Energy Transfer
- 2003
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 9:18, s. 4430-41
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Tidskriftsartikel (refereegranskat)abstract
- Compounds based on the 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY) framework are excellent fluorescent markers. When BODIPY dyes of this type are conjugated to functionalities that absorb at relatively short wavelengths, those functionalities can, in some molecules, transmit the absorbed energy to the BODIPY which then fluoresces. In such cases the BODIPY fragment acts as an acceptor while the other group serves as a donor. Energy transfer efficiencies in such donor-acceptor cassette systems must vary with the relative orientation of the two components, and with the structure of the linkers that attach them. This study was designed to probe these issues for the special case in which the linkers between the donor and acceptor fragments are conjugated. To do this, the cassettes 3-10 were prepared. Electrochemical studies were performed to provide insight into the degree of donor-acceptor conjugation in these systems. X-ray Crystallographic studies on single crystals of compounds 7 and 9 revealed the favored conformations of the donor and acceptor fragments in the solid state. Absorption, fluorescence, and time-resolved fluorescence spectra of the compounds were recorded, and quantum yields for the cassettes excited at the donor max were measured. Fluorescence steady-state anisotropy data were determined for cassettes 3 and 9 to provide information about the mutual direction of the transition dipole moments.
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