| 1. |
- de Boer, Erik J., et al.
(författare)
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Rapid succession of plant associations on the small ocean island of Mauritius at the onset of the Holocene
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 68, s. 114-125
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Tidskriftsartikel (refereegranskat)abstract
- The island of Mauritius offers the opportunity to study the poorly understood vegetation response to climate change on a small tropical oceanic island. A high-resolution pollen record from a 10 m long peat core from Kanaka Crater (560 m elevation, Mauritius, Indian Ocean) shows that vegetation shifted from a stable open wet forest Last Glacial state to a stable closed-stratified-tall-forest Holocene state. An ecological threshold was crossed at similar to 11.5 cal ka BP, propelling the forest ecosystem into an unstable period lasting similar to 4000 years. The shift between the two steady states involves a cascade of four abrupt (<150 years) forest transitions in which different tree species dominated the vegetation for a quasi-stable period of respectively similar to 1900, similar to 1100 and similar to 900 years. We interpret the first forest transition as climate-driven, reflecting the response of a small low topography oceanic island where significant spatial biome migration is impossible. The three subsequent forest transitions are not evidently linked to climate events, and are suggested to be driven by internal forest dynamics. The cascade of four consecutive events of species turnover occurred at a remarkably fast rate compared to changes during the preceding and following periods, and might therefore be considered as a composite tipping point in the ecosystem. We hypothesize that wet gallery forest, spatially and temporally stabilized by the drainage system, served as a long lasting reservoir of biodiversity and facilitated a rapid exchange of species with the montane forests to allow for a rapid cascade of plant associations.
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| 2. |
- Hessler, Ines, et al.
(författare)
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Millennial-scale changes in vegetation records from tropical Africa and South America during the last glacial
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:21-22, s. 2882-2899
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Tidskriftsartikel (refereegranskat)abstract
- To reconstruct the response of vegetation to abrupt climate changes during the last glacial we have compiled pollen records from the circum-Atlantic tropics between 23 degrees N and 23 degrees S from both marine and terrestrial sediment cores. Pollen data were grouped into mega-biomes to facilitate the comparison between the different records. Most tropical African records do not appear to register Dansgaard-Oeschger (D-O) variability, although there are vegetation changes during Heinrich Stadials (HS). There is a stronger signal of D-O and HS variability in the South American records. Records close to the modern northern and southern limits of the Intertropical Convergence Zone (ITCZ) show opposite trends in vegetation development during HS and D-O cycles. The pollen data from tropical South America corroborate the hypothesis of a southward shift in the migration pattern of the ITCZ and a reduction in the Atlantic Meridional Overturning Circulation (AMOC) during HS.
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| 3. |
- Nogué, Sandra, et al.
(författare)
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The human dimension of biodiversity changes on islands
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 372:6541, s. 488-491
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Tidskriftsartikel (refereegranskat)abstract
- Islands are among the last regions on Earth settled and transformed by human activities, and they provide replicated model systems for analysis of how people affect ecological functions. By analyzing 27 representative fossil pollen sequences encompassing the past 5000 years from islands globally, we quantified the rates of vegetation compositional change before and after human arrival. After human arrival, rates of turnover accelerate by a median factor of 11, with faster rates on islands colonized in the past 1500 years than for those colonized earlier. This global anthropogenic acceleration in turnover suggests that islands are on trajectories of continuing change. Strategies for biodiversity conservation and ecosystem restoration must acknowledge the long duration of human impacts and the degree to which ecological changes today differ from prehuman dynamics.
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