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- Larsson, Kjell, 1958-, et al.
(författare)
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Keeping up with early springs : rapid range expansion in an avian herbivore incurs a mismatch between reproductive timing and food supply
- 2009
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Ingår i: Global Change Biology. - Oxford : Blackwell Scientific. - 1354-1013 .- 1365-2486. ; 15:5, s. 1057-1071
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Tidskriftsartikel (refereegranskat)abstract
- Within three decades, the barnacle goose population wintering on the European mainland has dramatically increased in numbers and extended its breeding range. The expansion has occurred both within the Arctic as well as by the colonization of temperate areas. Studies of performance of individuals in expanding populations provide information on how well species can adapt to novel environments and global warming. We, therefore, studied the availability of high quality food as well as timing of reproduction, wing moult, fledgling production and postfledging survival of individually marked geese in three recently established populations: one Arctic (Barents Sea) and two temperate (Baltic, North Sea). In the Barents Sea population, timing of hatching was synchronized with the peak in food availability and there was strong stabilizing selection. Although birds in the Baltic and North Sea populations bred 6–7 weeks earlier than Arctic birds, timing of hatching was late in relation to the peak in food availability, and there was moderate to strong directional selection for early breeding. In the Baltic, absolute timing of egg laying advanced considerably over the 20-year study period, but advanced little relative to spring phenology, and directional selection on lay date increased over time. Wing moult of adults started only 2–4 weeks earlier in the temperate populations than in the Arctic. Synchronization between fledging of young and end of wing moult decreased in the temperate populations. Arctic-breeding geese may gradually accumulate body stores from the food they encounter during spring migration, which allows them to breed relatively early and their young to use the peak of the Arctic food resources. By contrast, temperate-breeding birds are not able to acquire adequate body stores from local resources early enough, that is before the quality of food for their young starts to decrease. When global temperatures continue to rise, Arctic-breeding barnacle geese might encounter similar problems.
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12. |
- Moortgat-Pick, G., et al.
(författare)
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Polarized positrons and electrons at the linear collider
- 2008
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Ingår i: Physics reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 460:4-5, s. 131-243
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Forskningsöversikt (refereegranskat)abstract
- The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.
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