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31.
西藏台错TT-1剖面厚369 cm,为一套碳酸盐粘土和粘土碳酸盐沉积,地层测年为41.4-4.5 ka,含丰富的轮藻化石,分属于11个轮藻植物群,群落所在地层的碳酸盐和钙质含量分别为80%和33%.从老到新(剖面自下而上):①41.4-26.64 ka(369-319 cm),处于末次冰期间冰阶MIS3a暖期,湖区气候... 相似文献
32.
David W. Hilbert Andrew Graham Mike S. Hopkins 《Palaeogeography, Palaeoclimatology, Palaeoecology》2007,251(1):104-118
An artificial neural network is used to classify environments, including climate, terrain and soil variables, according to their suitability for fifteen structural/environmental forest classes in the Wet Tropics Bioregion of north-east Queensland. We map the environments characteristic of these forest classes in four climate regimes (the present and three past climate scenarios), quantify the changes in area of these environments in response to past regional changes in climate and identify areas that would have been environmentally suitable for rainforests at last glacial maximum (glacial refugia). We also identify areas that would have been suitable for upland and highland rainforest classes during the warmest parts of the interglacial (interglacial refugia) and map locations that consistently remain favourable to specific forest classes despite large changes in climate.In the climate of the last glacial maximum (LGM), rainforest environments are predicted in three relatively distinct refugia in the northern, central and southern Wet Tropics. Only three percent of the total area contains lowland, Mesophyll Vine Forest and the majority of the area of the rainforest refugia supports upland rainforest classes. In the cool, wet climate of the Pleistocene/Holocene transition (PHT), rainforest environments expand to form a more or less continuous block from the northern limits of the region to the Walter Hill Range, except for discontinuous patches extending through the Seaview and Paluma Ranges in the south. During the Holocene climatic optimum (HCO), rainforest environments become more fragmented, especially in the south. Lowland rainforest environments are very extensive in this climate while upland rainforest classes are restricted to what we term “interglacial refugia”.Estimated distributions and stable locations (consistently predicted in all four climate scenarios) for the various rainforest environment classes are our main, novel contribution. Each forest environment responds individualistically to climate change. Our results confirm the highly dynamic nature of the Wet Tropics landscape and present a much more detailed picture of landscape change since the late Pleistocene than previously has been available. This mapping exercise should be useful in the future for analyses of present-day biogeographic patterns. We argue that empirical modelling approaches have an important role in palaeoecology and global change research that is complementary to the developing mechanistic methods. 相似文献
33.
SATISH K. SRIVASTAVA
FLS 《Botanical journal of the Linnean Society. Linnean Society of London》2011,167(2):235-248
Fossil grass pollen is common in Late Tertiary sediments and its rare occurrence in the Early Tertiary led to the belief that its presence is restricted to Tertiary sediments. A literature survey shows that rare occurrences of Graminidites spp. have been reported from Campanian–Maastrichtian strata worldwide. All reported Graminidites spp. have been studied by transmitted light microscopes, which are inadequate to resolve their fine exine sculpture. Graminidites sp. occurs in the Maastrichtian Scollard Formation of Alberta, Canada, and is studied here with light microscopy and scanning electron microscopy. A new species, G. ulkapites, occurs at the initiation of a temperate climate in the area. It occurs in post‐dinosaurian beds locally but in pre‐Cretaceous–Tertiary boundary strata, which implies that grasses could also be present in dinosaur inhabitations. Grass phytoliths, reported from dinosaurian coprolites from the Maastrichtian Deccan Intertrappean sediments of India, indicate that grasses were ingested by dinosaurs even if not included in the dinosaurian diet. A plot of worldwide Senonian occurrences of Graminidites spp. on a late Maastrichtian palaeogeographic map demonstrates that the data are inadequate to reveal the place of origin or migratory pattern. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 235–248. 相似文献
34.
Summary The microproblematicumPycnoporidium ? eomesozoicum
Flügel, 1972, from Upper Triassic reefs of the Alpine-Mediterranean region, Turkey Oman and Iran (originally interpreted as possible
alga) represents the type species of a new strophomenid brachiopod genus (Gosaukammerella n.g.). The genus is characterized by a very small, millimeter-sized plano-convex shell, whose ventral valve is attached to
the substratum (mainly sponges) by symmetrically arranged outgrowths developing from a pseudopunctate, lamellose foliated
shell wall and composed of densely spaced subparallel ‘tubes’ comparable with productide spines secreted by papillose extensions
of the mantle.Gosaukammerella seems to be the only reliable candidate for the existence of post-Paleozoic strophomenid (productid ?) brachiopods.
Gosaukammerella eomesozoica is restricted to possibly cryptic, shaded reef environments inhabited predominantly by sponges serving as substrates for
micromorphic brachiopods. 相似文献
35.
Somatic hybrids between Solanum bulbocastanum and potato: a new source of resistance to late blight 总被引:4,自引:0,他引:4
J. P. Helgeson J. D. Pohlman S. Austin G. T. Haberlach S. M. Wielgus D. Ronis L. Zambolim P. Tooley J. M. McGrath R. V. James W. R. Stevenson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):738-742
Solanum bulbocastanum, a wild, diploid (2n=2x=24) Mexican species, is highly resistant to Phytophthora infestans, the fungus that causes late blight of potato. However this 1 EBN species is virtually impossible to cross directly with
potato. PEG-mediated fusion of leaf cells of S. bulbocastanum PI 245310 and the tetraploid potato line S. tuberosum PI 203900 (2n=4x=48) yielded hexaploid (2n= 6x=72) somatic hybrids that retained the high resistance of the S. bulbocastanum parent. RFLP and RAPD analyses confirmed the hybridity of the materials. Four of the somatic hybrids were crossed with potato
cultivars Katahdin or Atlantic. The BC1 progeny segregated for resistance to the US8 genotype (A-2 mating type) of P. Infestans. Resistant BC1 lines crossed with susceptible cultivars again yielded populations that segregated for resistance to the fungus. In a 1996
field-plot in Wisconsin, to which no fungicide was applied, two of the BC1 lines, from two different somatic hybrids, yielded 1.36 and 1.32 kg/plant under a severe late-blight epidemic. In contrast,
under these same conditions the cultivar Russet Burbank yielded only 0.86 kg/plant. These results indicate that effective
resistance to the late-blight fungus in a sexually incompatible Solanum species can be transferred into potato breeding lines by somatic hybridization and that this resistance can then be further
transmitted into potato breeding lines by sexual crossing.
Received: 27 October 1997 / Accepted: 11 November 1997 相似文献
36.
吐鲁番-哈密盆地晚二叠世早期植物群 总被引:2,自引:1,他引:2
记述了吐鲁番-哈密盆地晚二叠世早期植物化石19属29种(包括6新种,2相似种和10未定种),这是一个以种子蕨类为主的安加拉型植物群。文中对这一植物群的性质和地质时代作了比较详细的讨论和对比。 相似文献
37.
《Comptes Rendus Palevol》2014,13(5):463-472
Late Cretaceous amber from La Garnache (France, Vendée) contains filamentous networks that have all the characteristics of spider webs. Using methods of classic and confocal microscopy, the web architecture and the thread structure are described. The geometry of the webs preserved in amber is presented in 3D imaging. Unlike most of the spider webs identified in amber, there are no regular radiating webs growing in two dimensions characteristic of the well-known orb web. A number of the characters would correspond to the apparently irregular organization of cob-type web or sheet web. By using confocal microscopy, we can highlight the preserved autofluorescence of spider silk proteins and new characters are proposed to identify the spider webs or fragments of webs in amber. 相似文献
38.
Roberta Pini 《Vegetation History and Archaeobotany》2002,11(4):251-262
The local and regional history of vegetation and climate, from the Late Glacial to the present, is represented in a new,
high-resolution pollen diagram from Pian di Gembro (1350 m asl), ten 14C dates providing a reliable time control. An open pioneer vegetation dominated by Artemisia, Gramineae, and and Chenopodiaceae followed the retreat of the glaciers after the Last Glacial Maximum. Shrub vegetation
with Juniperus, Alnus viridis, and Salix expanded soon after. Denser Betula-Pinus forests were present in Pian di Gembro around 12,320 B.P. Their extent was greatly reduced by the climatic cooling of the
Younger Dryas, when open vegetation spread again. The beginning of the Holocene was marked by a considerable expansion in
mixed oak taxa. Corylus immigrated to the site at 9,250 B.P. Picea and Abies expanded at 7,370 B.P., recording an abrupt change in the structure of the vegetational belts. A coeval climatic change is
evidenced in the GRIP records and also detectable through oscillations of the timberline. Signs of human impact are present
since late Atlantic, becoming more intense around 2,200 B.P. As pasture lands increased, Abies and Fagus slowly disappeared. The introduction of Castanea and Juglans is dated to Roman times, and Secale to the Middle Ages.
Received February 4, 2002 / Accepted August 2, 2002 相似文献
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