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Reading Agricultural Power 总被引：1，自引：0，他引：1
RUTH LIEPINS 《New Zealand geographer》1996,52(2):3-10
Many forms of rural geography include investigations of power. Lately some researchers have achieved this through studies of discourse. This paper presents a reading of agricultural power as it occurs in several examples of Australian and New Zealand print-media. Initially, I review the importance of discourse in the study of power - arguing that a ‘geography of discourse’ enables key questions and objects of analysis (spaces and processes) to be investigated. I then analyse coverage of agriculture in selected rural print-media forms. I argue that hegemonic discourses of masculinity and agriculture are used in the construction of reports, reinforcing the power of certain knowledges and truths. Finally, I propose more study is needed of the sites and processes through which meaning is constructed. Using the case of a farm women's conference I argue that the media involves a number of sites and processes which must be negotiated if discursive change is to occur in our understanding of agricuture. 相似文献
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RUTH WATKINS JAMES D. SCOURSE JUDY R. M. ALLEN 《Boreas: An International Journal of Quaternary Research》2007,36(2):170-181
Detailed pollen, charcoal and loss on ignition profiles were analysed from Llyn Cororion, North Wales, UK. The chronology was based on 11 radiocarbon dates. This site is particularly important for this region because its high-resolution record improves the spatial and temporal resolution of records of Holocene vegetation change in an area characterized by a highly variable environment. An early Holocene phase of Juniperus-Betula scrub was succeeded by Betula-Corylus woodland. Quercus and Ulmus were established by c. 8600 14C yr BP, with Pinus dominating at c. 8430 14C yr BP. Local disturbance then allowed the spread of Alnus; Tilia was a common component of the forest by 5650 14C yr BP. Charcoal and pollen records suggest that by c. 2600 14C yr BP there was progressive deforestation, increased use of fire and spread of grassland; the first cereal grain was recorded at c. 2900 14C yr BP. Compared with data from upland Snowdonia, the results show that within a topographically diverse region there were significant local variations in forest composition. These variations developed as a response to interactions between many environmental parameters and were further complicated by the influence of human activity. In an area such as North Wales it is therefore unlikely that one site can be representative of regional Holocene vegetational development. The site is additionally important because it contributes to the data available for meta-analyses of environmental change in the North Atlantic region, particularly as detailed pollen diagrams from coastal lake sites around western Europe are rare. 相似文献
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The Petrogenetic Significance of Interstratified High- and Low-Ti Basalts in Central Nicaragua 总被引：3，自引：0，他引：3
WALKER JAMES A.; CARR MICHAEL J.; FEIGENSON MARK D.; KALAMARIDES RUTH I. 《Journal of Petrology》1990,31(5):1141-1164
Basalts erupted from recent volcanoes in central Nicaragua canbe divided into distinct high-and low-Ti suites. Low-Ti basaltshave higher concentrations of LILE and LREE than high-Ti basalts.In addition, low-Ti basalts have obviously higher Ba/La, La/Sm,and 87Sr/86Sr, and lower Ti/Zr, than high-Ti basalts. In contrast,there are no mineralogical or petrographic differences betweenthe two suites. The differences between the high-and low-Ti basalts of centralNicaragua are inherited from their source regions. The primarymagmas of both are generated in the mantle wedge. However, low-Tiprimary magmas come from parts of the wedge which bear a strongsubduction zone signature, including that of subducted pelagicsediment. On the other hand, the primary magmas of the high-Tibasalts are generated in parts of the wedge relatively freeof subduction zone influence. Subducted pelagic sediment can therefore be a key source componentat active continental margins as well as at island arcs. Pelagicsediment could also be responsible for subtle high-field-strengthelement fractionations within subduction zone magmas. The mantlewedge beneath Nicaragua, which is variably modified by the subductingplate, is relatively enriched suboceanic mantle. 相似文献
4.
Mineral Chemistry of Peridotites from Paleozoic, Mesozoic and Cenozoic Lithosphere: Constraints on Mantle Evolution beneath Eastern China 总被引：24，自引：0，他引：24
ZHENG JIANPING; GRIFFIN WILLIAM L.; O'REILLY SUZANNE Y.; YANG JINSUI; LI TIANFU; ZHANG MING; ZHANG RUTH Y.; LIOU JOHN G. 《Journal of Petrology》2006,47(11):2233-2256
Major- and trace-element data on the constituent minerals ofgarnet peridotite xenoliths hosted in early Paleozoic (457–500Ma) kimberlites and Neogene (16–18 Ma) volcanic rockswithin the North China Craton are compared with those from thepre-pilot hole of the Chinese Continental Scientific DrillingProject (CCSD-PP1) in the tectonically exhumed Triassic (220Ma) Sulu ultrahigh-pressure (UHP) terrane along its southernmargin. P–T estimates for the Paleozoic and Neogene peridotitexenoliths reflect different model geotherms corresponding tosurface heat flows of 40 mW/m2 (Paleozoic) and 80 mW/m2 (Neogene).Garnet peridotite xenoliths or xenocrysts from the Paleozoickimberlites are strongly depleted, similar to peridotites fromother areas of cratonic mantle, with magnesium olivine (meanFo92.7), Cr-rich garnet and clinopyroxene with high La/Yb. Garnet(and spinel) peridotite xenoliths hosted in Neogene basaltsare derived from fertile mantle; they have high Al2O3 and TiO2contents, low-Mg-number olivine (mean Fo89.5), low-Cr garnetand diopside with flat rare earth element (REE) patterns. Thedifferences between the Paleozoic and Neogene xenoliths suggestthat a buoyant refractory lithospheric keel present beneaththe eastern North China Craton in Paleozoic times was at leastpartly replaced by younger, hotter and more fertile lithosphericmantle during Mesozoic–Cenozoic times. Garnet peridotitesfrom the Sulu UHP terrane have less magnesian olivine (Fo91.5),and lower-Cr garnet than the Paleozoic xenoliths. The diopsideshave low heavy REE (HREE) contents and sinusoidal to light REE(LREE)-enriched REE patterns. These features, and their highMg/Si and low CaO and Al2O3 contents, indicate that the CCSD-PP1peridotites represent a moderately refractory mantle protolith.Details of mineral chemistry indicate that this protolith experiencedcomplex metasomatism by asthenosphere-derived melts or fluidsin Mesoproterozoic, and subsolidus re-equilibration involvingfluids/melts derived from the subducted Yangtze continentalcrust during UHP metamorphism in the early Mesozoic. Tectonicextension of the subcontinental lithospheric mantle of the NorthChina Craton and exhumation of the Sulu UHP rocks in the earlyMesozoic induced upwelling of the asthenosphere. Peridotitessampled by the Neogene basalts represent newly formed lithospherederived by cooling of the upwelling asthenospheric mantle inJurassic–Cretaceous and Paleogene time. KEY WORDS: garnet peridotite xenoliths; North China Craton; lithospheric thinning; Sulu UHP terrane; UHP lithosphere evolution; mantle replacement 相似文献
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In this article we compile 108 national and international studies on global climate change, each projecting a quantitative impact on global surface-air temperature due to a doubling of the atmospheric CO2 concentration. These predictions, documented between 1980 and 1995, are based primarily on climate-modeling research, including radiative-convective, energy-balance, and general circulation models. Collectively over the past 15 years, the average (mean) temperature change projection due to doubled CO2 is +2.62°C, with a range of 0.16–8.7°C. General circulation models tend to estimate slightly higher values (2.98°C), compared with radiative-convective models (1.98°C) and energy-balance models (2.54°C). During the years 1980 through 1995, an increasing trend in predictions is noticed, although the mean temperature change prediction each year has remained fairly consistent near 2–3°C. These findings suggest that the estimated sensitivity of the climate system continues to remain comparable to the range calculated in earlier studies. However, tremendous advancements in the capacity of climate models continue to reveal important uncertainties in the dynamic nature of global atmospheric interactions. The predictions continue to validate the need for a global policy relating to human influence on global climate change. 相似文献
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Reliable quantification of suspended sediment (SS) and particulate phosphorus (PP) transport, and identification of the various delivery pathways at the catchment level, is an important and necessary aid to appropriate catchment management. In this study we measured storm event, seasonal and annual losses of SS and PP from a Danish arable catchment, Gelbæk Stream, using a multisampling strategy. SS losses for the study years May 1993–April 1994 and May 1994–April 1995 ranged from 71 to 88 kg ha−1, while PP losses ranged from 0·32 to 0·36 kg P ha−1. In both cases losses mainly occurred during infrequent storm events. In comparison with intensive storm sampling, infrequent (fortnightly) sampling underestimated annual transport during the two study years by −24 and −331%, respectively, for SS, and by −8·6 and −151%, respectively, for PP. Reliable estimation of the transport of sediment and sediment-associated nutrients and other substances thus necessitates the use of an intensive monitoring approach. Turbidimeters proved to be a good substitute for direct measurement of SS, especially during storm events, although careful calibration is needed at the seasonal and storm event levels. Experience shows that in artificially drained and geologically complex catchments such as Gelbæk, simultaneous comparative monitoring of different sources (e.g. subsurface drainage water) is an important means of reliably discriminating between the various diffuse sources of sediment and phosphorus. Subsurface drainage water was found to account for 11–15% of the annual SS export from the catchment; the corresponding figure for PP being 11–18%. Surface runoff was only a source of SS and PP during the first study year, when it accounted for 19% of SS and 7% of PP catchment export. Stream bank/bed erosion must therefore have been the major diffuse source of SS and PP in both study years. The study also revealed that analysis of the trace element content (e.g. 137Cs, 210Pb) of the SS transported in subsurface drainage water and stream water during storm events is a useful means of discriminating between diffuse losses of SS delivered from topsoil and subsoil compartments. © 1997 by John Wiley & Sons, Ltd. 相似文献
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Enriched End-member of Primitive MORB Melts: Petrology and Geochemistry of Glasses from Macquarie Island (SW Pacific) 总被引：13，自引：4，他引：9
KAMENETSKY VADIM S.; EVERARD JOHN L.; CRAWFORD ANTHONY J.; VARNE RICK; EGGINS STEPHEN M.; LANYON RUTH 《Journal of Petrology》2000,41(3):411-430
Macquarie Island is an exposure above sea-level of part of thecrest of the Macquarie Ridge. The ridge marks the Australia–Pacificplate boundary south of New Zealand, where the plate boundaryhas evolved progressively since Eocene times from an oceanicspreading system into a system of long transform faults linkedby short spreading segments, and currently into a right-lateralstrike-slip plate boundary. The rocks of Macquarie Island wereformed during spreading at this plate boundary in Miocene times,and include intrusive rocks (mantle and cumulate peridotites,gabbros, sheeted dolerite dyke complexes), volcanic rocks (N-to E-MORB pillow lavas, picrites, breccias, hyaloclastites),and associated sediments. A set of Macquarie Island basalticglasses has been analysed by electron microprobe for major elements,S, Cl and F; by Fourier transform infrared spectroscopy forH2O; by laser ablation–inductively coupled plasma massspectrometry for trace elements; and by secondary ion mass spectrometryfor Sr, Nd and Pb isotopes. An outstanding compositional featureof the data set (47·4–51·1 wt % SiO2, 5·65–8·75wt % MgO) is the broad range of K2O (0·1–1·8wt %) and the strong positive covariation of K2O with otherincompatible minor and trace elements (e.g. TiO2 0·97–2·1%;Na2O 2·4–4·3%; P2O5 0·08–0·7%;H2O 0·25–1·5%; La 4·3–46·6ppm). The extent of enrichment in incompatible elements in glassescorrelates positively with isotopic ratios of Sr (87Sr/86Sr= 0·70255–0·70275) and Pb (206Pb/204Pb =18·951–19·493; 207Pb/204Pb = 15·528–15·589;208Pb/204Pb = 38·523–38·979), and negativelywith Nd (143Nd/144Nd = 0·51310–0·51304).Macquarie Island basaltic glasses are divided into two compositionalgroups according to their mg-number–K2O relationships.Near-primitive basaltic glasses (Group I) have the highest mg-number(63–69), and high Al2O3 and CaO contents at a given K2Ocontent, and carry microphenocrysts of primitive olivine (Fo86–89·5).Their bulk compositions are used to calculate primary melt compositionsin equilibrium with the most magnesian Macquarie Island olivines(Fo90·5). Fractionated, Group II, basaltic glasses aresaturated with olivine + plagioclase ± clinopyroxene,and have lower mg-number (57–67), and relatively low Al2O3and CaO contents. Group I glasses define a seriate variationwithin the compositional spectrum of MORB, and extend the compositionalrange from N-MORB compositions to enriched compositions thatrepresent a new primitive enriched MORB end-member. Comparedwith N-MORB, this new end-member is characterized by relativelylow contents of MgO, FeO, SiO2 and CaO, coupled with high contentsof Al2O3, TiO2, Na2O, P2O5, K2O and incompatible trace elements,and has the most radiogenic Sr and Pb regional isotope composition.These unusual melt compositions could have been generated bylow-degree partial melting of an enriched mantle peridotitesource, and were erupted without significant mixing with commonN-MORB magmas. The mantle in the Macquarie Island region musthave been enriched and heterogeneous on a very fine scale. Wesuggest that the mantle enrichment implicated in this studyis more likely to be a regional signature that is shared bythe Balleny Islands magmatism than directly related to the hypotheticalBalleny plume itself. KEY WORDS: mid-ocean ridge basalts; Macquarie Island; glass; petrology; geochemistry 相似文献
8.
KR. M. JENSEN M.Sc. RUTH HELKIÆR JENSEN M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):34-51
Jensen, Kr. M. and Jensen R. Helkiær: En landbrugsgeografisk analyse af Gadbjerg og Givskud sogne. Geografisk Tidsskrift 76: 34—51. København juni 1. 1977. The agricultural development in two parishes in a former heath region in Central Jylland has been investigated. The expansion of farmland up to the turn of the century was especially in Givskud replaced by a regression period with afforestation of marginal areas. The farmers are now increasing the size of their holdings and the specialization on few crops involves a more uniform land-use. 相似文献
9.
Late Pleistocene to Holocene palaeoenvironmental variability in the north‐west Spanish mountains: insights from a source‐to‐sink environmental magnetic study of Lake Sanabria 
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