62 resultados para Allele frequency data


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Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn - Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (µ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at ~3500-3300 and ~3000-2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns.

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This data set contains a time series of plant height measurements (vegetative and reproductive) from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In addition, data on species specific plant heights for the main experiment are available from 2002. In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. 1. Plant height was recorded, generally, twice a year just before biomass harvest (during peak standing biomass in late May and in late August). Methodologies of measuring height have varied somewhat over the years. In earlier year the streched plant height was measured, while in later years the standing height without streching the plant was measured. Vegetative height was measured either as the height of the highest leaf or as the length of the main axis of non-flowering plants. Regenerating height was measured either as the height of the highest flower on a plant or as the height of the main axis of flowering. Sampled plants were either randomly selected in the core area of plots or along transects in defined distances. For details refer to the description of individual years. Starting in 2006, also the plots of the management experiment, that altered mowing frequency and fertilized subplots (see further details in the general description of the Jena Experiment) were sampled. 2. Species specific plant height was recorded two times in 2002: in late July (vegetative height) and just before biomass harvest during peak standing biomass in late August (vegetative and regenerative height). For each plot and each sown species in the species pool, 3 plant individuals (if present) from the central area of the plots were randomly selected and used to measure vegetative height (non-flowering indviduals) and regenerative height (flowering individuals) as stretched height. Provided are the means over the three measuremnts per plant species per plot.

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A detailed survey of the Mittelgrund in Eckernförde Bay shows slope breaks at 10-12 m and 15-16 m water depth. They are thought to be mainly the result of marine abrasion. Utilizing records from the Edgerton mud-penetrator, a map of holocene sediment thickness has been drawn. From the pattern of bottom echos 4 types of stratification can be recognized. An interpretation of them is attempted, as they are supposed to serve as models for other transgression contacts.