How special are Etendeka mesas? Flora and elevation gradients in an arid landscape in north-west Namibia

Seven mesas (i.e. flat-topped, isolated mountains) and the Grootberg mountain in arid north-west Namibia were investigated with regard to floristic relationships in relation to environmental gradients. Relationships between mesas and their surrounding, species richness and number of mesa specialists were used as measures to explore the influence of elevation on these floristic parameters. Also soil properties were investigated along these elevation gradients. The overall questions were designed to investigate the importance, i.e. ‘special status’, of these mesas in terms of contributing to species diversity and to elucidating ecological processes in this arid landscape.With regard to special floristic status, the tops of mesas supported different plant communities than their surrounding plains, while slopes indicated various levels of intermingling with plain vegetation. Differences between mesas and plains became more pronounced with increasing elevation. There were, however, no clear vegetation belts related to elevation. Plant species richness and number of mesa specialists showed a trend of increasing numbers with elevation, but these trends were statistically poorly supported, largely due to high variability between samples.Do soil gradients and elevation, as two important environmental variables, affect this ‘special’ status? Pronounced soil gradients were evident for many soil properties. These in combination with altitudinal effects of increased moisture and lower temperatures were believed to directly influence plant species composition and richness. The soil gradients may also indicate nutrient flow from the mesas to the surrounding lowlands, a process of ecological importance, particularly should degradation due to over grazing become a problem in the lowland areas.     

南秦岭宁陕地区月河坪夕卡岩型钼矿Re-Os年龄和矿床学特征

宁陕地区月河坪钼矿床位于南秦岭多金属成矿带,属于夕卡岩型钼矿。本文采用辉钼矿Re-Os同位素定年方法,精确地测定月河坪钼矿的成矿时代。分析结果显示,5件辉钼矿样品Re-Os同位素模式年龄的变化范围小,集中在189.8Ma和195.4Ma之间,获得加权平均年龄值191.4±1.6Ma,与等时线回归计算得到的年龄值193.6±3.5Ma在误差范围内相吻合。结果说明成矿时代为早侏罗纪,成矿作用属于中国北部燕山期大规模成矿期的一部分。结合已报道的成矿年龄资料,月河坪钼矿床可能形成于扬子板块与华北板块的后碰撞造山作用过程,但有可能受到后期岩浆活动的改造和破坏。同时推测在南秦岭地区存在印支末期到燕山早期的成矿事件,这对于秦岭造山带尤其是南秦岭地区钼矿资源勘探具有借鉴意义。     

Maximum extent and readvance dynamics of the Irish Sea Ice Stream and Irish Sea Glacier since the Last Glacial Maximum

The BRITICE-CHRONO Project has generated a suite of recently published radiocarbon ages from deglacial sequences offshore in the Celtic and Irish seas and terrestrial cosmogenic nuclide and optically stimulated luminescence ages from adjacent onshore sites. All published data are integrated here with new geochronological data from Wales in a revised Bayesian analysis that enables reconstruction of ice retreat dynamics across the basin. Patterns and changes in the pace of deglaciation are conditioned more by topographic constraints and internal ice dynamics than by external controls. The data indicate a major but rapid and very short-lived extensive thin ice advance of the Irish Sea Ice Stream (ISIS) more than 300 km south of St George's Channel to a marine calving margin at the shelf break at 25.5 ka; this may have been preceded by extensive ice accumulation plugging the constriction of St George's Channel. The release event between 25 and 26 ka is interpreted to have stimulated fast ice streaming and diverted ice to the west in the northern Irish Sea into the main axis of the marine ISIS away from terrestrial ice terminating in the English Midlands, a process initiating ice stagnation and the formation of an extensive dead ice landscape in the Midlands.     

Extensional tectonics and mid-Paleozoic massive sulfide occurrences in Europe

The age and lithologic settings of mid-Paleozoic massive sulfide deposits in Central Europe and southwest Iberia are suggestive of extensional tectonic environments. This inference is supported by the facies configurations of contemporaneous clastic sediments, the presence of deepwater lithologies and pelagic faunas, and marked mafic-felsic bimodalism in associated volcanic rocks.The massive sulfide deposits of the Moravia-Silesia area, Rammelsberg, Meggen, and other deposits appear to have formed in the same tectonic environment: one dominated by crustal extension. The important massive sulfide deposits of the southwest Iberian province formed somewhat later, but appear to be related to a phase of crustal extension initiated in late Devonian time.These two sets of rifting (sensu latu) events correlate in time with Caledonide collision in the north and subsequent Acadian collision further south. The postulated extensional events thus may relate directly to these collisions.All the areas under consideration were subsequently affected by Hercynian compressional events. The high potash granites associated with Hercynian collisions are largely the products of crustal melting and consequently have associated with them ore deposits characterized by lithophile elements such as tin, tungsten and uranium. A significant fraction of the Paleozoic metallogeny of Europe can thus be understood in terms of extensional tectonic events followed by compressional events less than 100 m.y. later.

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Zusammenfassung Das Alter und die lithologische Zusammensetzung von massiven Sulfiderzlagerstätten des Devons in Mittel-Europa und Südwest-Iberien deuten auf eine Ausweitungstektonik. Diese Hypothese wird bekräftigt durch die Fazieskonfiguration gleichalter klastischer Sedimente, das Auftreten von Tiefseeablagerungen und pelagischen Faunen, und die ausgesprochen mafisch-felsische Bimodalität von assoziierten Vulkaniten.Die massiven Sulfidlagerstätten von Mähren und Schlesien, Rammelsberg, Meggen und andere Vorkommen scheinen sich unter den gleichen tektonischen Bedingungen gebildet zu haben, nämlich unter Dehnungseffekten der Kruste. Die wichtigsten massiven Sulfidlagerstätten der südwestlichen Iberischen Provinz entstanden etwas später, sie scheinen einer Dehnungsphase beginnend im höheren Devon zugeordnet zu sein.Diese zwei Phasen eines Riftings (sensu lato) stimmen zeitlich mit der kaledonischen Kollision im Norden und der darauffolgenden akadischen Kollision weiter südlich überein. Die angenommenen Dehnungsvorgänge können daher direkt mit diesen Kollisionen in Verbindung gebracht werden.Alle besprochenen Gebiete sind in der Folge von herzynischen Einengungs-Erscheinungen betroffen worden. Die hochgradig kali-haltigen Granite, die den herzynischen Kollisionen zugeordnet sind, sind größtenteils die Ergebnisse von krustalen Schmelzvorgängen und haben deshalb assoziierte Erzlagerstätten, die durch lithophile Elemente wie Zinn, Wolfram und Uran gekennzeichnet sind. Ein beträchtlicher Teil der paläozoischen Metallogenese Europas kann daher aus der Sicht distraktiver tektonischer Erscheinungen gesehen werden, deren Einengungs-Vorgänge weniger als 100 Millionen Jahre später folgten.

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Résumé L'âge et la composition lithologique des gisements de sulferes massifs du Paléozoïque moyen de l'Europe Centrale et du sud-ouest de la Péninsule ibérique suggèrent un environement tectonique de distension. Cette hypothèse est appuyée par la configuration des facies des sédiments clastiques contemporains, la présence de lithologies d'eau profonde et de faunes pélagiques et par l'existence d'un net bimodalisme mafique-felsique dans les roches volcaniques associées.Les importants gisements de sulfere de Moravie et de Silésie, du Rammelsberg, de Meggen et autressemblent s'être formés sous un régime tectonique semblable, principalement sous l'effet de distensions de la croûte. Les gisements du sud-ouest de la Péninsule ibérique se sont formés un jeu plus tard, mais semblent être liés à une phase de distension crustale ayant débutéau Dévonien supérieur.Ces deux séries de ruptures (sensu latu) sont corrélés dans le temps avec la collision calédonienne au nord et la collision acadienne subséquente plus au sud.Les évènements de distension invoqués peuvent done être directement liés à ces collisions.Toutes les régions considérées ici furent affectées plus tard par la compression hercynienne. Les granites à haute teneur en potasse, liés aux collisions hercyniennes sont, en grande partie, des produits de la fusion crustale. Ils sont par conséquent associés à des gisements de minerais d'étain, de tungstène et d'uranium. Une partie importante de la métallogénie paléozoïque de l'Europe peut être ainsi comprise en termes d'événements tectoniques de distensions suivis moins de 100 millions d'années plus tard, par une compression.

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厄尔尼诺和南方涛动对中国水稻产量的影响

This paper aims to demonstrate the relationships between ENSO and rice production of Jiangxi province in order to identify the reason that ENSO might have little effect on Chinese rice production. Using a data set with measures of Jiangxi's climate and rice production,we find the reason that during 1985 and 2004 ENSO's well correlated with rainfall did not promote Chinese rice production. First,the largest effects of ENSO mostly occur in the months when there is no rice in the field. Second,there is almost ...     

Perceptions of Environmental Change and Climate Concern Among Idaho’s Farmers

Climate change public opinion research has identified conservative political ideology as the primary predictor of skepticism about climate change’s anthropogenic causes. Most farmers in Idaho are politically conservative, but they are also a unique group for whom observing their environment is part of daily life and work. We use data from in-depth interviews with 30 Idaho farmers to examine the relationship between observations of specific environmental changes and climate concern. We find that while most farmers report noticing changes in precipitation patterns, growing season length, and winter temperatures, few farmers connect these with long-term global climate change. These findings have two important implications: 1) direct experience, even in the form of disruption to an individual’s economic security, is not enough to overcome the influence of political ideology on climate change beliefs, and 2) acknowledging climate variation is not sufficient to convince individuals that the changes are produced by human activities.     

西加拿大波利尔平原地表水富营养化管理技术

Surface waters in western Canada often experience eutrophication-related problems with water quality, specifically high internal phosphorus loading rates and excessive phytoplankton and macrophyte production, that lead to water column anoxia and restricted fisheries habitat. A group of researchers from across Canada were involved for a seven-year period in cooperative programs for surface water quality management in western Canada, based at the University of Alberta. This paper summarises information on two techniques, hypolimnetic oxygenation and lime (Ca₂CO₃ and Ca(OH)₂) application, used in western Canada (specifically, the province of Alberta) to manage eutrophication in standing waters (lakes and reservoirs).     

The case for an international commission for the conservation and management of sharks (ICCMS)

The current rate of shark global exploitation and mortality is arguably so high under current management regimes that unless a renewed initiative is undertaken some species of shark will become effectively extinct. Current efforts to sustainably manage shark mortality are driven primarily by domestic laws in a few countries, big international non-governmental organizations (BINGOs) promoting environmental laws in the countries or regions where they exist, a handful of regional fisheries management organizations (e.g., IATTC and ICCAT), and inter-governmental organizations such as CITES. The absence of enforcement capability is often argued as the critical component in the failure to protect sharks from overexploitation. The remedy advanced here goes far beyond the need for stepped up enforcement, and calls for the creation of an entirely new international management regime, the International Commission for the Conservation and Management of Sharks (ICCMS). Such an agency could learn from the experiences of management bodies tasked with conservation of species biologically similar to sharks, such as the International Whaling Commission (IWC), to improve its efficacy. Critics have identified many organizational flaws that reduced the IWC’s effectiveness during its earliest years. Some of those flaws are examined here and remedies are suggested that an ICCMS could use to create a more effective management regime. The life histories of elasmobranches and large whales are compared to illustrate their similarities as a biological foundation for the selection of the IWC as a model.     

Weathering the escarpment: chemical and physical rates and processes,south‐eastern Australia

Differences in chemical weathering extent and character are expected to exist across topographic escarpments due to spatial gradients of climatic and/or tectonic forcing. The passive margin escarpment of south‐eastern Australia has a debated but generally accepted model of propagation in which it retreated (within 40 Ma) to near its current position following rifting between Australia and New Zealand 85–100 Ma before present. We focus on this escarpment to quantify chemical weathering rates and processes and how they may provide insight into scarp evolution and retreat. We compare chemical weathering extents and rates above and below the escarpment using a mass balance approach coupling major and trace element analyses with previous measurements of denudation rates using cosmogenic nuclides (¹⁰Be and ²⁶Al). We find a slight gradient in saprolite chemical weathering rate as a percentage of total weathering rate across the escarpment. The lowlands area, encompassing the region extending from the base of the escarpment to the coast, experiences a greater extent of chemical weathering than the highland region above the escarpment. Percents of denudation attributable to saprolite weathering average 57 ± 6% and 47 ± 7% at low and high sites respectively. Furthermore, the chemical index of alteration (CIA), a ratio of immobile to mobile oxides in granitic material that increases with weathering extent, have corresponding average values of 73·7 ± 3·9 and 65·5 ± 3·4, indicating lower extents of weathering above the escarpment. Finally, we quantify variations in the rates and extent of chemical weathering at the hillslope scale across the escarpment to suggest new insight into how climate differences and hillslope topography help drive landscape evolution, potentially overprinting longer term tectonic forcing. Copyright © 2009 John Wiley & Sons, Ltd.