震后银厂沟资源环境可持续发展研究

银厂沟坐落于龙门山脉中段,在汶川大地震中,银厂沟资源环境遭受很大损失,山体滑坡崩塌,堰塞湖的形成,地形地貌的变形,生态系统破坏等,严重影响当地的旅游业。针对这些问题提出相应的恢复重建的方案,保证当地经济的可持续发展具有重要的意义。     

Parthenocarpy, attractiveness and seed predation by birds in Bursera morelensis

Parthenocarpy (production of seedless fruits) is a characteristic associated with a strategy to reduce seed predation by birds and to increase the attractiveness to frugivorous birds. Red cuajiote (Bursera morelensis) is an endemic tree species of Mexico that produces seeded and parthenocarpic fruits. The purpose of this work was to examine whether parthenocarpy is a factor that increases the number of bird visits to trees and if it is a strategy to diminish seeds predation by granivorous birds. We made field observations to determine the relation between the number of bird visits and fruit removal rate, to the total number of parthenocarpic fruits produced, and the number of birdpredated fruits to the number and proportion of parthenocarpic fruits in the trees. We found that in trees with a bigger amount of parthenocarpic fruits, both frugivoruos and granivorous birds made more visits; we then suggested that parthenocarpic fruits can act like a signal of attraction by means of a density and coloration effect. Also, we found that in trees with bigger proportions of parthenocarpic fruit, predation by granivorous birds is smaller. Parthenocarpy has an adaptative value for B.morelensis increasing bird visitation and reducing seed predation in the Tehuacan Valley.     

Assessing gaps in irrigated agricultural productivity through satellite earth observations—A case study of the Fergana Valley,Central Asia

Improving crop area and/or crop yields in agricultural regions is one of the foremost scientific challenges for the next decades. This is especially true in irrigated areas because sustainable intensification of irrigated crop production is virtually the sole means to enhance food supply and contribute to meeting food demands of a growing population. Yet, irrigated crop production worldwide is suffering from soil degradation and salinity, reduced soil fertility, and water scarcity rendering the performance of irrigation schemes often below potential. On the other hand, the scope for improving irrigated agricultural productivity remains obscure also due to the lack of spatial data on agricultural production (e.g. crop acreage and yield). To fill this gap, satellite earth observations and a replicable methodology were used to estimate crop yields at the field level for the period 2010/2014 in the Fergana Valley, Central Asia, to understand the response of agricultural productivity to factors related to the irrigation and drainage infrastructure and environment. The results showed that cropping pattern, i.e. the presence or absence of multi-annual crop rotations, and spatial diversity of crops had the most persistent effects on crop yields across observation years suggesting the need for introducing sustainable cropping systems. On the other hand, areas with a lower crop diversity or abundance of crop rotation tended to have lower crop yields, with differences of partly more than one t/ha yield. It is argued that factors related to the infrastructure, for example, the distance of farms to the next settlement or the density of roads, had a persistent effect on crop yield dynamics over time. The improvement potential of cotton and wheat yields were estimated at 5%, compared to crop yields of farms in the direct vicinity of settlements or roads. In this study it is highlighted how remotely sensed estimates of crop production in combination with geospatial technologies provide a unique perspective that, when combined with field surveys, can support planners to identify management priorities for improving regional production and/or reducing environmental impacts.     

Reconstruction of Alpine Cenozoic paleorelief through the analysis of caves at Siebenhengste (BE,Switzerland)

Abstract

The cave region of Siebenhengste, situated north of Lake Thun (Switzerland), contains one of the most important cave systems in the world, which extends from 500 to 2000 m a.s.l. It has a complex multiphase history. The recognized speleogenetic phases are related to spring level and to old valley floors. The six most recent phases were investigated in St. Beatus cave and Bärenschacht. They suggest a progressive Quarternary Aare valley incision to 890, 805, 760, 700, 660, and 558 m a.s.l. that is confirmed by statistical analysis of small caves. U/Th-datings of flowstone allowed a timing of the valley deepening phases: the valley bottom was at 760 m already before 350 ka, the one at 700 m was active between 235 and 160 ka. The cave morphology in the upper part of the cave system was coupled with sedimentological observations. This combination leads to the hypothesis that the uppermost (oldest) cave parts were already created in the Miocene, during and after the last deposition of the Molasse. Ideas about the evolution of the paleorelief suggest that today's Aare valley is a product of glacial erosion, and that the old Aare valley shifted its position several times between the Miocene and today. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.     

珠江流域岩石风化作用消耗大气/土壤CO2量的估算

以流域的岩性、径流量和水化学分析数据为主要资料,利用基于GIS空间分析的GEM-CO2模型,估算珠江流域陆地岩石风化作用消耗大气/土壤空气中的CO2,评价河流流域的碳汇能力。结果表明,珠江流域因岩石溶蚀和风化作用消耗大气/土壤中的CO2量为252×109 mol·a-1(571×103 mol·km-2·a-1),从岩性分析,碳酸盐岩区大气/土壤CO2消耗量为180×109 mol·a-1(1030×103 mol·km-2·a-1),占总量的71.4%。二级流域以西江流域CO2消耗量最大,占珠江流域总CO2消耗量79.4%,北江、东江分别占总量的13.0%、4.9%。珠江流域大气/土壤CO2消耗量大约为世界大河流域平均值的2.3倍。     

Dispersion Pattern of PGE and Ag in Chromiferous Ultramafic Suite of Rocks in Sukinda Valley,India

Potential chromite ore deposits of India are situated in Sukinda, Odisha, which may also be considered as a potential resource for platinum group elements (PGEs). This paper reports on PGE geochemistry in twenty six samples covering chromite ores, chromitites and associated ultramafic rocks of the Sukinda ultramafic complex. Platinum group element contents range from 213 to 487 ppb in the chromite ore body, from 63 to 538 ppb in rocks that have chromite dendrites or dissemination and from 38 to 389 ppb in associated olivine–peridotite, serpentinite, pyroxenite and brecciated rocks. The PGEs are divided into two sub‐groups: IPGE (Ir, Os, and Ru) and PPGE (Pd, Pt, and Rh) based on their chemical behaviour. The IPGE and PPGE in these three litho‐members show a contrasting relationship e.g. average IPGE content decreases from chromite to chromitite and associated rocks while PPGE increases in the same order. Appreciable Ag in chromitite (270–842 ppb) is recorded. Positive correlation between IPGE with Cr₂O₃ and with Al₂O₃ is observed while these are negatively correlated with MgO. Covariant relationships between Au and Mg in rocks devoid of chromite and between Ag and Fe in chromitite sample are observed. Chromite in all seams and some chromitite samples exhibit an IPGE‐enriched chondrite normalized pattern while PPGE are highly fractionated and show a steep negative slope, thereby indicating that PGE in the parental melt fractionates and IPGE‐compatible elements prefer to settle with chromite. The rocks devoid of chromite and rocks containing accessory chromite exhibit a nearly flat pattern in chondrite‐normalized PGE plots and this suggests a limited fractionation of PGE in these rocks. Variation in the distribution pattern of PGE and Ag in three typical litho‐members of the Sukinda Valley may be related to multiple intrusion of ultramafic magma, containing variable volume percentage of chromite.     

Late Palaeozoic 40Ar/39Ar ages of the HP-LT metamorphic rocks from the Kekesu Valley,Chinese southwestern Tianshan: new constraints on exhumation tectonics

abstract

Although numerous ages have been obtained for the Chinese southwestern Tianshan high pressure/ultrahigh pressure-low temperature (HP/UHP-LT) metamorphic belt in the past two decades, its exhumation history is still controversial. The poor age constraint was related to the appealing low metamorphic temperatures and excess Ar commonly present under HP/UHP conditions. This study aims to provide new age constraints on the orogen’s exhumation by obtaining ⁴⁰Ar/³⁹Ar mica ages using the conventional step-heating technique, with emphasis on the avoidance of excess Ar contamination. From a cross section along the Kekesu Valley, four samples, three from the HP-LT metamorphic belt (TK050, TK051, and TK081) and one from the southern margin of the low pressure metamorphic belt (TK097), were selected for ⁴⁰Ar/³⁹Ar dating. Phengites from garnet glaucophane schist TK050 and the surrounding rock garnet phengite schist TK051 yield comparable plateau ages of 321.4 ± 1.6 and 318.6 ± 1.6 Ma, respectively, while epidote mica schist TK081 gives a younger plateau age of 293.3 ± 1.5 Ma. Considering the chemical compositions of phengites, mineral assemblages, and microstructures in the thin slices, we suppose that the former represents the time the HP rocks retrograded from the peak stage (eclogite facies) to the (epidote)-blueschist facies, whereas the latter reflects greenschist facies overprinting. Biotite and muscovite from two-mica quartzite TK097 give similar plateau ages of 253.0 ± 1.3 and 247.1 ± 1.2 Ma, interpreted to date movement on the post collisional transcrustal South Nalati ductile shear zone. By combining our new ages with published data, a two-stage exhumation model is suggested for the Chinese southwestern Tianshan HP/UHP-LT metamorphic belt: initial fast exhumation to a depth of about 30–35 km by ~320 Ma was followed by relatively slow (~1 mm year^–1) uplift to ~10 km by ~293 Ma.     

莫坝-希拉沟地区水系沉积物地球化学特征及找矿

莫坝-希拉沟地区16个元素水系沉积物测量地球化学特征研究表明,贫乏元素有Au、Hg、Mo;正常元素有Cu、Pb、Zn、Co、Mn、W、Sn、Bi;富集元素有As、Sb、Ag、Fe、Ni;无强富集的元素。通过各元素空间分布研究,对主要地球化学异常进行推断解释,指出三叠系地层、尤其与喷出岩有关的地区是寻找Cu、Pb、Zn、Au、Ag等多金属矿的有利地区。     

The role of NTFPs in a shifting cultivation system in transition: A village case study from the uplands of North Central Vietnam

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 103–114, 2006

Periods characterized by agricultural change and transitions are often associated with insecurity and vulnerability regarding food production and food supplies. Forests and forest products tend to play an important buffer role during the process of change and uncertainty, where forest and fallows provide food products or income that people can temporarily fall back on. In the upland village of Que in North Central Vietnam, several different drivers are currently changing land use and land cover. The Forest Land Allocation policy, implemented in 1998, is one of the major driving forces, allocating farmers a reduced area of land for shifting cultivation in order to prevent any further deforestation and land degradation. However, the reduction in agricultural land set aside for shifting cultivation has lead to a severe decrease in hill rice production. The land use system is in a transition phase—from a conventional shifting cultivation system to a composite swiddening system. The area under shifting cultivation has been reduced, and the system has been intensified via the introduction of paddy rice cultivation, increased livestock rearing and commercial exploitation of non-timber forest products (NTFPs). Yet, the current transformation of the system has resulted in a drastic reduction in overall rice production. Thus, the collection and selling of NTFPs such as bamboo shoots, broom grass and pherynium leaves seem to prevent severe shortage of food since farmers are able to purchase food products with the money generated from the selling of NTFPs.     

THE ORAL HISTORY OF GEOGRAPHY∗

Book Reviewed in this article:

Latin America: Case Studies. Richard G. Boehm and Sent Visser

Locality and Rurality: Economy and Society in Rural Regions. Tony Bradley And Philip Lowe

The City and the Grassroots. Manuel Castells

Geopolitics and Conflict in South America. Quarrels among Neighbors. Jack Child

Post-Industrial America: A Geographical Perspective. David Clark

Coastal Research: UK Perspectives. Malcolm W. Clark

A Rural Policy for the EEC? Hugh Clout

Peasant Agriculture in Assam: A Structural Analysis. M. M. Das.

Environmental Change and Tropical Geomorphology. I. Douglas and T. Spencer

Advances in Abandoned Settlement Analysis: Application to Prehistoric Anthrosols in Colombia, South America. Robert C. Eidt

Measuring Culture. Jonathan L. Gross and Steve Rayner

North America: A Human Geography. Paul Guinness and Michael Bradshaw

A Geographical Bibliography for American Libraries. Chauncy D. Harris et al.

Geography and the Urban Environment: Progress in Research and Applications, Vol. VI. D. T. Herbert and R. J. Johnston

Changes in Global Climate: A Study of the Effect of Radiation and Other Factors During the Present Century. K. Ya. Kondrat'ev.

Rural Development and the State: Contradictions and Dilemmas in Developing Countries. David A. M. Lea and D. P. Chaudhri

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Weather and Climate. Paul E. Lydolph.

Spatial Divisions of Labor: Social Structures and the Geography of Production. Doreen Massey.

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Soviet Armenia. K. S. Demirchian.

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Phenomenology, Science and Geography: Spatiality and the Human Sciences. John Pickles.

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Social and Economic Aspects of Radioactive Waste Disposal: Considerations for Institutional Management

World-Wide Weather. K. Takahashi

Coastal Geomorphology in Australia. B. G. Thom

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Ethics in Planning. Martin Wachs