Consequences of land use change for ecosystem services: A future unlike the past

This study investigates the implications of past and future land use change for two ecosystem services provided by terrestrial vegetation: net primary production, which is the basis of the food chain, and modulation of climate through exchanges of energy, water, and momentum between the land surface and atmosphere. At the global scale, the most extensive land use change over the past several centuries occurred in temperate areas with cropland expansion in fertile areas. This type of conversion has generally increased net primary production due to water and nutrient inputs to mechanized agriculture and cooled surface climate due to increased albedo. In contrast, future land use change is projected to occur predominantly in the humid tropics, with large reductions in net primary production and a warming effect due to decreased transpiration. In the past, the effects of land use change on NPP and surface climate are not substantially outside the range of decadal-scale interannual variability. Future land use change alters these ecosystem services outside this range. The consequences of land use change in the coming decades are likely to be fundamentally different than in the past.     

Applicability of the rectangular hyperbolic method to settlement predictions of sabkha soils

In this paper, the applicability of the hyperbolic method to predict settlements of sabkha formations was investigated. Conventional and long-term consolidation tests were conducted, and the fit of the experimental data to a rectangular hyperbolic relationship was examined. The validity of the hyperbolic form as a representation of the settlement-time response of sabkha soils was further ascertained by analysing settlement records measured under an instrumented test embankment. The laboratory results indicated that the settlement-time behaviour could reasonably be represented by the hyperbolic relationship. Settlement estimates determined as the inverse of the slope of the initial linear segment multiplied by the slope of the theoretical curve, or obtained based on the radial slopes corresponding to 50% and 90% consolidation points, all underestimated the observed total settlements. However, the inverse of the slope of the final linear segment of the hyperbolic curve gave excellent estimates of the observed total settlements. The agreements between the predicted and observed in situ ultimate primary consolidation settlements are considered reasonable. Finally, except when the hyperbolic plot follows a straight line, the use of the hyperbolic method for prediction of total settlements of sabkha soils with prominent secondary compression behaviour has been shown to be both uncertain and impractical.     

An understanding of geography: The perspectives of English primary trainee teachers

There have been few studies of trainee teachers' conceptions of the term ‘geography’. Building on these, this study identifies a number of conceptions of geography held by primary school trainee teachers in England. Their ideas are compared with their understanding of the reasons for teaching geography to young children. Similar outcomes emerge. While a small number of primary trainee teachers see geography education as concerned with the study of places, a slightly larger group view teaching geography as developing children's sense of responsibility for the earth and its people. However, by far the largest groups of students perceive geography's role to be to develop younger children's awareness and knowledge of the environment. Additionally, a sizeable group of trainees see geography as providing knowledge about the features and countries of the world. The implications of these findings are considered for the brief geography study units which primary teacher trainees take as part of their initial teacher training programme in English higher education. The conclusion is that it is important to widen primary trainee teachers' perspectives during even the briefest of units, not least to enable them to teach the national curriculum requirements for geography in primary schools. This revised version was published online in August 2006 with corrections to the Cover Date.     

Geographic Information Systems: A Tool to Support Geography and Environmental Education?

Geographic information systems (GIS) education is at a crossroads in the United States. Since its inception in the early 1990s, GIS has diffused slowly into select groups of K-12 classrooms through the efforts of geography and environmental educators. However, many of the assumptions underpinning the initial period of enthusiasm for the technology are now being questioned. This paper reviews issues identified as barriers to dissemination in order to help shape and inform the next phase of GIS implementation. First, the existing arguments for GIS in elementary and secondary education in the United States are reviewed and evaluated. Second, considerations related to developing an improved pedagogical foundation for GIS are explored. Finally, implications and suggestions for guidelines for the next decade of dissemination and implementation of GIS are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

青藏铁路冻土路基沉降变形现场试验研究

Based on the field data of ground temperature and roadway settlement observed during the construction of the experimental embankments over permafrost along the Qinghai-Tibetan Railway, this paper discusses the differences of frost process on the roadway surface from that on the natural ground surface, the changes of permafrost table under the roadway embankment, and the peculiarities of roadway settlement. Analyses of the test results show : 1) The differences of the freezing indexes between the roadway surfaces and the natural ground surfaces are less than those of the thawing indexes for all the test sections; 2) Since the measures of permafrost protection were taken, the permafrost tables under the embankments have raised after the roadway was constructed. The minimum is about 0.4 m and the maximum is 1.2 m; 3) the settlements of the roadway are mainly from the compression and creep of the icerich frozen soils under the original permafrost tables and the maximum has reached 6 ～ 8 cm during the first year after the embankments were constructed. Moreover, concerning the processes of roadway settlement, the deformation of the embankments has no obvious trend of attenuation at present. Especially,for the roadway with high embankments, the settlement may reach a remarkable value and much consideration must be given for this problem.     

太湖流域洪涝灾害评估模型

在地理信息系统支持下建立了太湖流域DEM模型,并建立了全流域12类共24种土地利用类型、2194个圩区、1012个乡镇和94个报汛站点的空间数据库及属性数据库。在此基础上,根据实时报汛资料,通过插值得到各乡汛期圩外水位和降雨量。圩区采用排涝计算圩内内涝水量再与DEM叠加,非圩区用乡最高水位与DEM叠加,可获得全流域淹没水深栅格数据。统计不同乡镇、不同土地类型、不同淹没水深的淹没面积,并根据当年的社会经济数据,建立了太湖流域洪涝灾害损失评估模型。对1999年太湖流域洪涝灾害评估结果表明,模型具有一定的精度,可为流域防洪减灾决策提供依据。     

城市快速道路软基处理方案探讨

介绍了深厚软土地基地质条件及处理技术要求,进行了软基处理的技术经济对比并选择了相应方案。此外,对选择的方案进行了参数设计及沉降分析预测。该方案实施后,取得了明显的经济效益。     

Genetic geographies. A historical comparison of agrarian modernization and eugenic thought in Germany, the Soviet Union, and the United States

The article deals with the role of genetics in the state-led agricultural modernization efforts that took place in different industrialized countries during the course of the 1920s and 1930s. A comparison between Germany, the Soviet Union and the United States shows substantial similarities in their attempts to increase the productivity of agriculture on different geographical scales. Following advances in scientific knowledge about the geography of cultivated plants, these countries sent out numerous expeditions to collect plant breeding material from all over the world. At the same time, states tightened their grip on farmers’ and breeders’ activities inside the country by establishing legal rules for the use of plant varieties and seed. But this was only one side of a larger “genetic modernization” project. In all three countries, concepts of agricultural modernization were substantially linked to social-darwinist thought which embraced programs of eugenics and “racial hygiene”. These links are outlined for each of the cases, highlighting the widely differing intermingling of scientific concepts and terminologies with political ideologies. It is then discussed what role geography and in particular geopolitical thinking of the time were to play in the development of “genetic modernization”, and more specifically, with regard to the nexus between agriculture and eugenics. While the discipline’s involvement in both fields remained comparably marginal in practical terms, clearly there were conceptual contributions toward the development of the broader field. Going back to Ratzel’s and Kjellén’s work, it is argued that geography had an important role in the establishment of a political field in which ideas of managing human reproduction were fused with concepts of economic development and environmental determinism.     

1990年代以来国外商业地理研究进展

本文在翻阅大量文献资料的基础上，分析了1990年代以来国外商业地理研究进展，总结出国外商业地理研究的9个主要研究方向，以期对中国的商业地理学研究和商业发展有所借鉴。     

人文地理学研究方法述要

人文地理学是地理学的重要分支学科，20世纪60年代在人文地理学领域内进行的计量革命引发了人们对地理学的理论建设以及地理学方法论 思考，但是计量革命从一开始就经历着种种责难，文章从对计量革命这一运动的观察开始，对人文地理学方法论进行了反思，在此基础上对当前人文地理学采用的方法进行概括总结，并对一些研究方法应用前景予以展望。