Human and Environmental Factors Affect Patterns of Crop Diversity in an Ethiopian Highland Agroecosystem     

Leah H. Samberg  Carol Shennan  Erika S. Zavaleta 《The Professional geographer》2013,65(3):395-408

The Ethiopian highlands are a center of diversity for numerous globally important crops. Heterogeneous landscapes, traditional agricultural practices, and inaccessibility have created and maintained diverse subsistence agroecosystems. We surveyed sixty-three farms in twelve communities of the Gamo highlands and found high levels of on-farm diversity of crop species and varieties. The extent and nature of this diversity are related to both ecological factors, namely elevation, and anthropogenic factors such as land-use history, accessibility to markets and extension, and strength and scale of farmer exchange networks. These human landscape features have the potential to both enhance and mediate effects of elevation and other environmental factors on crop diversity. The interaction of environmental and anthropogenic forces on the diversity of crops grown by farmers affects the strategies farmers employ to adapt their farming to changing conditions.  相似文献   

LOCATING EMPLOYMENT GROWTH IN URBAN AREAS TO MINIMIZE TRAVEL TIME     

《The Professional geographer》2013,65(2):149-155

The transportation requirements of an urban area are, in part, a function of its land use pattern. Reducing travel in an urban area by effective land use design appears to be a worthwhile public policy objective. The planning model derived in this article uses as its core the matrix version of the Lowry model developed by Garin. The model allocates basic employment to the zones of an urban area in order to minimize work and service trips. A hypothetical planning problem for Metropolitan Toronto illustrates use of the model.  相似文献   

Spatial Scale and Population Assignment Choices in Environmental Justice Analyses 1     

《The Professional geographer》2013,65(4):574-586

Abstract

Environmental justice laws protect certain populations against discriminatory actions that may result from a myriad of enterprises, including transportation activities. Previous environmental equity studies examining the effects of transportation-engendered externalities have been criticized on several points, including (1) that the choice of a reference population for comparison to the criterion variable may influence the outcome of research results and (2) that the selection and use of inappropriate methodologies intended to identify and characterize populations may foreordain research outcomes. This article examines the potentially confounding effects of selected spatial scale and population assignment strategies as applied to a study of excessive noise levels at a large Midwestern airport, finding that reported outcomes can vary significantly as a function of methodological choices.  相似文献   

Twenty years of land use and livelihood changes in SE-Niger: Obsolete and short-sighted adaptation to climatic and demographic pressures?     

《Journal of Arid Environments》2013

This paper explores the evolution of land use and natural resource management strategies over the past twenty to fifty years in a remote Sahelian region. The empirical example is Karagou village in SE Niger. Building on an in-depth survey from 1992 and a targeted, follow-up analysis of contemporary land use strategies in 2011, the change process is scrutinized.The analysis uses the conceptual lenses of land systems science, human–environmental timelines, and the notion of multiple exposures. Enabling and constraining conditions for local livelihoods in terms of the resource base (landscape, water, and population) are described. Results characterize how land use strategies have developed and how local people opportunistically use different landscape elements such as dune landscapes, valley bottoms (bas-fonds) and oases (cuvettes). Major concerns are rainfall variability, saturation of cropland, and perceived dwindling groundwater resources. It is concluded that the land use and livelihood strategies have remained remarkably stable in the face of the changing socio-ecological fringe conditions, but that this situation may hamper a sustainable transformation.  相似文献   

The emerging small-scale cattle farming sector in Uzbekistan: Highly integrated with crop production but suffering from low productivity     

《Journal of Arid Environments》2013

Even two decades after independence in 1991, the agricultural sector of Uzbekistan remains regulated by the government, prescribing the number of cattle head per agricultural area or imposing mandatory cash crops. The policy makers are insufficiently informed about the bottlenecks in the different livestock production units and base their policies mainly on general knowledge. This study analyzed the two major cattle farm types in the Khorezm province, 56 medium-scale farms (LS; on average 22 ha) and 80 household farms (HH; on average 0.2 ha). While LS farms produced more metabolizable energy and crude protein than required by their own ruminant livestock, the feeds produced by HH farms covered only a third of the requirements. Despite their limited farm size, the HH farmers took an active part in the commercial farming sector, for example, through the purchase of inputs for cattle and crop production, and product sales. The HH farms generated higher relative crop yields than their LS counterparts, while cattle productivity of both was comparable, albeit low. The present findings can be considered as a benchmark for monitoring developments in the cattle sector and as a source of information for directing improvements in feed supply, cattle health and husbandry.  相似文献   

Gendered Spaces of Informal Entrepreneurship in Soweto,South Africa   总被引：1，自引：1，他引：0  

Richard Grant 《Urban geography》2013,34(1):86-108

Abstract

The full diversity of economic activities in the informal economy is not well understood. The apartheid legacy of limiting informal entrepreneurship explains the most obvious geographical patterns in South Africa. After a decade and a half since the end of apartheid, however, knowledge about the places from which informal entrepreneurs operate is incomplete. Retailing is overemphasized and production firm entrepreneurs, both male and female, remain a neglected spatiality. This study reports on a survey of 100 firms in Soweto and in-depth interviews with 30 firm owners. The findings challenge the representations of isolated urban entrepreneurs dependent on inherited social capital and of women's exclusive engagement in retail. Entrepreneurs create their own social capital in work-related realms, but there are important gender differences. More finely tuned conceptualizations of entrepreneurs and of gendered working spaces need to be developed so that policy does not perpetuate unitary myths and incomplete spatial representations. [Key words: entrepreneurship, Soweto, informal economy, gender.]  相似文献   

雪崩防治工程研究与应用现状     

刘大翔  程尊兰  赵鑫  黄金辉  刘建康 《山地学报》2013,31(4)

雪崩是对高寒山区房屋、设施、道路安全威胁最大的自然灾害之一.在目前雪崩监测预警技术还很不完善的情况下,发展灾害防治工程技术是避免或减轻雪崩对人类生命财产损失的重要措施.对国际上常用雪崩防治工程进行分类,重点按作用手段分别阐述了各种防治工程的研究与应用现状,对防治工程研究进展、适用范围、设计要求、应用情况等关键问题进行了总结和探讨.研究认为,目前的雪崩灾害防护工程存在修筑标准欠缺、雪崩机理不明确、工程设计参数计算不合理、试验模拟不理想、基础理论研究落后于实践活动等不足,并建议从工程综合配置、雪崩与防护结构相互作用、工程设计参数定量化研究、开发积雪清理技术、构建监测预警系统等方面开展先行工作.  相似文献   

A Review of: “Applications of Spatial Data Structures: Computer Graphics,Image Processing,and GIS”. By H. SAMET. (Addison-Wesley Publishing Company,Inc, 1989.) [Pp. xv + 507; figures,tables, appendix,references, name and credit index,subject index.] Price US $49.95. ISBN 020150300 X (hardback).     

WOLFGANG KAINZ 《International journal of geographical information science》2013,27(2):253-254

The introduction of automated generalisation procedures in map production systems requires that generalisation systems are capable of processing large amounts of map data in acceptable time and that cartographic quality is similar to traditional map products. With respect to these requirements, we examine two complementary approaches that should improve generalisation systems currently in use by national topographic mapping agencies. Our focus is particularly on self‐evaluating systems, taking as an example those systems that build on the multi‐agent paradigm. The first approach aims to improve the cartographic quality by utilising cartographic expert knowledge relating to spatial context. More specifically, we introduce expert rules for the selection of generalisation operations based on a classification of buildings into five urban structure types, including inner city, urban, suburban, rural, and industrial and commercial areas. The second approach aims to utilise machine learning techniques to extract heuristics that allow us to reduce the search space and hence the time in which a good cartographical solution is reached. Both approaches are tested individually and in combination for the generalisation of buildings from map scale 1:5000 to the target map scale of 1:25 000. Our experiments show improvements in terms of efficiency and effectiveness. We provide evidence that both approaches complement each other and that a combination of expert and machine learnt rules give better results than the individual approaches. Both approaches are sufficiently general to be applicable to other forms of self‐evaluating, constraint‐based systems than multi‐agent systems, and to other feature classes than buildings. Problems have been identified resulting from difficulties to formalise cartographic quality by means of constraints for the control of the generalisation process.  相似文献   

Rapid generation of Digital Elevation Models from topographic maps     

Lars Eklundh  Ulrik Mårtensson 《International journal of geographical information science》2013,27(3):329-340

Abstract

In this article we demonstrate that substantial gains in time can be made when using point sampling rather than contour line digitising for generation of Digital Elevation Models (DEMs). A simple sampling scheme, based on regularly distributed points, was used supplemented with points near break-lines in the terrain. An evaluation of surfaces created with three different interpolation methods at three different resolutions shows that the statistical distribution was better when using points as opposed to contours, and that the accuracy was comparable despite the much smaller amount of input data.  相似文献   

Community-based production of geographic information using open source software and Web 2.0     

G. Brent Hall  Raymond Chipeniuk  Robert D. Feick  Michael G. Leahy  Vivien Deparday 《International journal of geographical information science》2013,27(5):761-781

This article presents an innovative approach to citizen-led production of Web-based geographic information where new and/or existing digital map features are linked to annotations or commentary and citizens engage in synchronous and/or asynchronous discussion. The article discusses the relationship of the approach to public participation geographic information systems (PPGISs) and the emerging challenges associated with volunteered geographic information. A custom-developed, open source software tool named MapChat is used to facilitate the citizen inputs and discussions. The information generated from applying the approach through a series of community workshops is presented and discussed in light of current issues in PPGIS and volunteered geographic information research.  相似文献