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Wetter Climate (wetter + climate)
Selected AbstractsTectono-sedimentary evolution of the northernmost margin of the NE German Basin between uppermost Carboniferous and Late Permian (Rotliegend)GEOLOGICAL JOURNAL, Issue 1 2001H. Rieke Abstract The tectono-sedimentary evolution of the Rotliegend deposits of the northernmost margin of NE German Basin (NEGB) has been analysed on the basis of detailed sedimentary logs of 300,m of core material together with the re-evaluation of 600,km of seismic lines. Three distinct phases were recognized. During the initial Phase I, basin geometry was largely controlled by normal faulting related to deep-seated ductile shearing leading to a strong asymmetric shape, with a steep fault-controlled eastern margin and a gently, dipping western margin. The results of forward modelling along a cross-section fit the basin geometry in width and depth and reveal a footwall uplift of c. 1000,m. Adjacent to the steep faults, local sedimentation of Lithofacies Type I was confined to non-cohesive debris flow-dominated alluvial fans, whereas the gently dipping western margin was dominated by alluvial-cone sedimentation. During the post-extensional period (Phase II), cooling of the lithosphere generated additional accommodation space. The sediments of Lithofacies Type II, comprising mainly clast-supported conglomerates, are interpreted as braided ephemeral stream flow-surge deposits. Tectonic quiescence and an increase in flood events resulting from wetter climate led to progradation of this facies over the entire region. At the end of this period, the accommodation space was almost completely filled resulting in a level topography. Phase III was controlled by the thermal-induced subsidence of the southerly located NEGB in post-Illawarra times. The formerly isolated region tilted towards the SW, thus forming the northern margin of the NEGB during uppermost Havel and Elbe Subgroup times. The sediments of Lithofacies Type III were divided into a marginal sandstone-dominated environment and a finer-grained facies towards the SW. The former consists of poorly-sorted coarse-grained sandstones of a proximal and medial ephemeral stream floodplain facies. The latter comprise mud flat fines and fine-grained distal ephemeral stream deposits. The end of the tectono-sedimentary evolution is marked by the basinwide Zechstein transgression. Copyright © 2001 John Wiley & Sons, Ltd. [source] Variation in Serripes groenlandicus (Bivalvia) growth in a Norwegian high-Arctic fjord: evidence for local- and large-scale climatic forcingGLOBAL CHANGE BIOLOGY, Issue 9 2006WILLIAM G. AMBROSE Jr. Abstract We examined the growth rate of the circumpolar Greenland Cockle (Serripes groenlandicus) over a period of 20 years (1983,2002) from Rijpfjord, a high-Arctic fjord in northeast Svalbard (80°10,N, 22°15,E). This period encompassed different phases of large-scale climatic oscillations with accompanying variations in local physical variables (temperature, atmospheric pressure, precipitation, sea ice cover), allowing us to analyze the linkage between growth rate, climatic oscillations, and their local physical and biological manifestations. Standard growth index (SGI), an ontogenetically adjusted measure of annual growth, ranged from a low of 0.27 in 2002 up to 2.46 in 1996. Interannual variation in growth corresponded to the Arctic climate regime index (ACRI), with high growth rates during the positive ACRI phase characterized by cyclonic ocean circulation and a warmer and wetter climate. Growth rates were influenced by local manifestations of the ACRI: positively correlated with precipitation and to a lesser extent negatively correlated with atmospheric pressure. A multiple regression model explains 65% of the variability in growth rate by the ACRI and precipitation at the nearest meteorological station. There were, however, complexities in the relationship between growth and physical variables, including an apparent 1 year lag between physical forcing changes and biological response. Also, when the last 4 years of poor growth are excluded, there is a very strong negative correlation with ice cover on a pan-arctic scale. Our results suggest that bivalves, as sentinels of climate change on multi-decadal scales, are sensitive to environmental variations associated with large-scale changes in climate, but that the effects will be determined by changes in environmental parameters regulating marine production and food availability on a local scale. [source] Demography and population dynamics of Drosera anglica and D. rotundifoliaJOURNAL OF ECOLOGY, Issue 1 2004J.-F. Nordbakken Summary 1We studied demography and population dynamics of the sympatric perennial herbs Drosera anglica and D. rotundifolia on a boreal bog in SE Norway. Dry mass of 2872 D. anglica plants and 2467 D. rotundifolia plants (estimated from field morphological measurements) was used to classify plants into five species-specific size classes. Demographic changes within these two populations were followed from 1995 to 1999, and within segments (quartiles) along the water table gradient and the peat productivity gradient. 2Mortality was strongly size dependent, and varied between years, for both species; it was high for seedlings, low for the smallest mature rosettes and increased again for the largest mature rosettes. The proportion of fertile rosettes increased with increasing rosette size. Fecundity varied considerably between years, but little relative to gradient position. 3Growth rate (,) was > 1, except in the second year, when it fell to 0.572 for D. anglica and 0.627 for D. rotundifolia . For D. anglica small, but significant, differences were found between the two extremities of the water table gradient, and for D. rotundifolia between the second and the uppermost quartile. There was a tendency for D. anglica populations to have a lower growth rate in the most productive sites, whereas D. rotundifolia grew less on both low and high peat productivity. Elasticity analysis showed that stasis and size increase (primarily within mature stages) made major contributions to , for D. anglica in all years. 4The variance in population growth rate (var ,) was high between years, and higher for D. anglica than for D. rotundifolia , while the variance between quartiles along the two main gradients was low. Life-table response experiment (LTRE) analyses revealed that for both species, differences in probabilities of transitions within mature stages, and in growth to larger stages, contributed most to var ,. 5The effects of global warming are uncertain: drier growing seasons would affect Drosera populations negatively, while initially positive responses to a wetter climate may be balanced by competition from increased Sphagnum growth. [source] Does biogeographical history matter?AUSTRAL ECOLOGY, Issue 1 2005Diversity, distribution of lotic midges (Diptera: Chironomidae) in the Australian Wet Tropics Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal gradients within the Wet Tropics revealed a fauna of 87 species-level taxa in 49 genera comprising three main elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an enduring effect of the historical rainforest contractions on current-day distribution patterns. These findings contrast with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity gradient does not apply to the Australian chironomid fauna. [source] Does biogeographical history matter?AUSTRAL ECOLOGY, Issue 1 2005Diversity, distribution of lotic midges (Diptera: Chironomidae) in the Australian Wet Tropics Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal gradients within the Wet Tropics revealed a fauna of 87 species-level taxa in 49 genera comprising three main elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an enduring effect of the historical rainforest contractions on current-day distribution patterns. These findings contrast with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity gradient does not apply to the Australian chironomid fauna. [source] Ecomorphometric variation and sexual dimorphism in the common shrew (Sorex araneus)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2009T. A. WHITE Abstract We investigated the evolution of the biomechanics of the mandible in island and mainland populations of the common shrew on the west coast of Scotland. We predicted that climatic differences between populations should cause differences in prey composition leading to changes in the mechanical potential (MP) of the mandible. In females, MP was correlated with climate, with greater MP in warmer and drier habitats. In males, MP was significantly greater than in females but there was no relationship between male MP and climate. This led to increased sexual dimorphism in colder and wetter climates. The same pattern was found after a phylogenetic least squares analysis was conducted to account for shared phylogenetic history. We discuss possible reasons for this pattern, including male,male combat and the greater necessity of females to feed as efficiently as possible to meet their extremely high energy requirements during lactation. [source] | ||||||||||