应用ISSR标记分析三江平原狭叶甜茅不同种群的遗传多样性     

沈光  倪红伟  徐香玲 《湿地科学》2006,4(4):286-291

以三江平原狭叶甜茅(Glyceriaspiculosa)为研究对象,选取3个不同群落类型:狭叶甜茅优势种群落、狭叶甜茅和毛苔草(Carexlasiocarpa)为共建种的群落以及狭叶甜茅为主要伴生种的群落,共45个材料进行了ISSR分子标记分析。结果从41个引物中筛选出7个有效引物,扩增出80条清晰条带,平均每个引物扩增了11.4条带,其中70个位点是多态的,总的多态位点比率为87.5%,表明被测材料间ISSR标记多态性较高。利用Popgen(version1.32)软件分析了扩增结果,并得到了狭叶甜茅不同群落类型的遗传距离、遗传一致度、Nei和Shannon信息指数等遗传特征。结果表明,对于一个物种来说,当地理距离太近不能成为影响其遗传多样性水平的因素时,其构成的种群在群落中的地位将是影响遗传多样性水平的主要因素之一。  相似文献   

Mercury behaviour during tropical weathering： Evidence from a Brazilian soil profile developed on diabase     

《中国地球化学学报》2006,25(B08):242-242

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Weathering characteristics of arctic islands in northern Norway     

yvind Paasche  Jrund Raukleiv Strmse  Svein Olaf Dahl  Henriette Linge 《Geomorphology》2006,82(3-4):430-452

The arctic islands of the Lofoten-Vesterålen archipelago in northern Norway have a wide distribution of weathered land surfaces commonly located above 250 m with several apparent similarities. In order to investigate the characteristics of (deep) weathering in this region, northern Langøya and Hadseløya were chosen for in-depth analyses. Eight weathering profiles were excavated from various surfaces, and the stratigraphies were logged in detail. Material was collected throughout the weathering horizons, and all samples were subsequently analysed for clay mineralogy (< 63 μm fraction) and grain size distribution. The sampling strategy was complemented by samples from additional saprolites and other landforms such as moraines and rock glaciers. The XRD results indicate that the presence of secondary minerals, such as gibbsite (Al(OH)₃) and kaolinite (Al₂Si₂O₅(OH)₄), are very common throughout the profiles. Gibbsite is an extreme end product of silicate weathering and usually associated with a warmer and more humid climate, as found in Scandinavia during the Tertiary. The grain size analyses (< 63 μm) show that the finer silt fractions (< 8 μm) tend to be high in the profiles (20–40%), with significant amounts of clay (5–15%) demonstrating that the regolith itself is susceptible to frost sorting mechanisms.¹⁰Be exposure dates from in situ quartz knobs on tors and boulders of local origin suggest > 40,000 years of subaerial conditions. Considering the steady surface erosion, this figure should be viewed as an absolute minimum age estimate. Mapping of the superficial sediments and geomorphological features of the study areas has revealed several common morphological features, which indicate dominance of glacial and periglacial processes in the areas lying below the lower boundary of blockfields (c. 250 m). The weathering mantles are not a periglacial end product, but rather a relict tertiary landform that were modulated by permafrost processes as well as biological processes at later stages. The regolith cover constrain the vertical extension of warm-based Quaternary ice sheets challenging the notion of a parabolic ice mass consuming every mountain top of Lofoten and Vesterålen.  相似文献   

Racism and Intolerance in Eastern Australia: a geographic perspective     

James Forrest  Kevin Dunn 《The Australian geographer》2006,37(2):167-186

Racism has become a fact of life in Australia over the past decade or so, yet there are relatively few studies of its nature or extent, and still fewer on its geography. Using a social constructivist approach, this study draws on a survey of 5056 respondents to investigate attitudes to racism and cultural diversity in New South Wales and Queensland, and of perceptions of out-groups as instances of ‘strangers in our midst’. On racism, results show the presence of a continuum of attitudes ranging from generally tolerant to generally intolerant, a presence which cuts across compositional (social or aspatial) characteristics to emphasise the existence of a distinctive geography, an everywhere different nature to racist and non-racist attitudes which transcends urban–rural and traditional social layers. On the other hand, perceptions of out-groups are not uniformly correlated with presence or absence of cultural diversity. In many cases, the ability to make judgements about significant ‘others’ or out-groups has been shown to relate more to abstract notions of self and national identity, reproduced in public by mainstream news media and political leaders. In particular, it may reflect an Anglo (or Anglo-Celtic) view on nationalism, which is a hallmark of the ‘new racism’: an assimilationist or ethnocultural view of Australian society which is different from the ‘civic nation’ ideal envisaged by multiculturalism. That the geography of attitudes and perceptions people have towards and about different cultural groups is so ‘everywhere different’ has important implications for attempts to address and redress issues of intolerance in Australia.  相似文献   

Seaweed floristic studies along tsunami affected Indian coasts: A litmus test scenario after 26th December 2004     

Vaibhav A Mantri 《Journal of Earth System Science》2006,115(3):371-378

On 26th December 2004, the world witnessed the devastating power of tsunami, affecting many countries, bordering the Indian Ocean region. This has caused significant changes in the shallow and intertidal regions of the Indian coast, especially the Andaman and Nicobar Islands, Tamil Nadu, Kerala and Pondicherry. The baseline data on biomass availability and distribution of benthic intertidal seaweed species were collected immediately after this catastrophic event by spot surveying 11 selected localities of the above-mentioned regions. In all, 45 species belonging to 31 genera were recorded during the present survey, the maximum number of seaweed species were recorded at Thirumullavarum, Kerala with the minimum at Car Nicobar, Andaman and Nicobar Islands. A very different trend was observed in the case of biomass availability at some locations which was due to the influence of habitat suitability over the tsunami damage. The details of this study have been provided in the present communication  相似文献   

杨庄截潜工程趾板段帷幕灌浆效果分析     

张文珍 《华南地质与矿产》2006,(1):72-76

杨庄截潜工程趾板段建基面以下为弱风化白云岩和含燧石条带白云岩,透水性较强,造成库水漏失严重.为解决建基面以下基岩渗漏问题,采用趾板段帷幕灌浆封堵基岩裂隙而形成防渗帷幕,以减少库水漏失.通过趾板段帷幕灌浆达到封堵基岩裂隙的目的,满足工程设计的防渗要求.  相似文献   

利用钻孔超声成像的图像特征进行岩石风化程度分类   总被引：2，自引：0，他引：2  

孔广胜 《物探与化探》2005,29(4):367-368,373

钻孔超声成像方法能精确地反映井壁的光滑情况, 进而判断岩石的风化发育程度, 确定风化层的厚度。阐述了钻孔超声成像的走时和振幅图像特征, 给出了1个在香港地区的应用实例。  相似文献   

The effect of rock moisture on Schmidt hammer rebound: tests on rock samples from Marion Island and South Africa     

Paul Sumner  Werner Nel 《地球表面变化过程与地形》2002,27(10):1137-1142

In an assessment of the influence of internal rock moisture content on Schmidt hammer readings, rebound (R) values are found to decrease with increasing moisture content. For samples of basalt, sandstone and dolerite the maximum decrease in R‐values is found between oven dry values and saturated rock rebound values, the magnitude of which varies from 2 to 10 points on the R‐scale. A quartzite block has the greatest decline of 6 points at 60 per cent saturation. For certain rock types under differing site‐to‐site field moisture conditions the moisture effect can be a significant factor in the interpretation of the relative state of weathering from rebound values. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

碳酸盐岩差异性风化成土特征及其对石漠化形成的影响   总被引：35，自引：0，他引：35  

孙承兴  王世杰  周德全  李瑞玲  李艳丽 《矿物学报》2002,22(4):308-314

碳酸盐岩极低的酸不溶物含量使岩石风化产生的残积土壤物质数量极少，并产生巨大的体积缩小，促使早期形成的残积土在重力作用下不断向下塌陷。显著的差异性风化使基岩面强烈起伏，甚至形成大量的岩溶尘洼地、裂隙、地下管道、洞穴系统等。在重力和水的作用下，土粒沿垂直和水平方向上经微距离或短距离搬运到上述低洼或地下空间中，甚至由地下河带到更远的地方，这是碳酸盐岩地区土壤丢失的重要方式，也是形成石漠化最主要的地质因素。土壤在地表分布高度不均匀，是碳酸盐岩地区的地表少土的重要原因。对于酸不溶物含量相当的石灰岩和白云岩而言，由于白云岩的差异性风化明显弱于石灰岩，以及受各种应力作用后，白云岩形成的节理及裂隙密集而均匀，从而提高了近地表白云岩的含水能力，延长了风化过程中的水－岩反应时间，使风化作用可以相对集中于地表或近地表进行，有利于岩石的整体风化作用的进行，同时使白云岩风化壳基岩面起伏相对较小，风化残积形成的土壤分布也相对均匀。因此，白云岩区地表土层较厚，石漠化程度也稍弱于灰岩区。  相似文献   

Small-Mammal Data on Early and Middle Holocene Climates and Biotic Communities in the Bonneville Basin, USA     

Dave N. Schmitt  David B. Madsen  Karen D. Lupo 《Quaternary Research》2002,58(3):255

Archaeological investigations in Camels Back Cave, western Utah, recovered a series of small-mammal bone assemblages from stratified deposits dating between ca. 12,000 and 500 ¹⁴C yr B.P. The cave's early Holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and/or sagebrush (e.g., Lepus townsendii, Marmota flaviventris, Reithrodontomys megalotis, and Brachylagus idahoensis) which suggest that the region was relatively cool and moist until after 8800 ¹⁴C yr B.P. Between ca. 8600 and 8100 ¹⁴C yr B.P. these mammals became locally extinct, taxonomic diversity declined, and there was an increase in species well-adapted to xeric, low-elevation habitats, including ground squirrels, Lepus californicus and Neotoma lepida. The early small-mammal record from Camels Back Cave is similar to the 11,300–6000 ¹⁴C yr B.P. mammalian sequence from Homestead Cave, northwestern Utah, and provides corroborative data on Bonneville Basin paleoenvironments and mammalian responses to middle Holocene desertification.  相似文献