共查询到20条相似文献,搜索用时 46 毫秒
1.
Maria Salonen Tuuli ToivonenJean-Michel Cohalan Oliver T. Coomes 《Applied geography (Sevenoaks, England)》2012,32(2):501-513
Quantitative measures of accessibility are increasingly used in land cover change modeling and in assessing human pressure on the environment. In riverine Amazonia the significance of physical accessibility for biodiversity, land use patterns and economic livelihoods is widely acknowledged, but attempts to quantify accessibility in practice have been few in number. In this study we compare different distance- and frequency-based measures of spatial accessibility and develop a quantitative model of accessibility patterns for the north-eastern Peruvian Amazonia where rivers form the core of the transportation network. We model accessibility between the rural areas of the Loreto region and the capital city of Iquitos, using different distance algorithms in a geographic information system, and complement the distance model with information on river boat frequencies and transport capacities. Patterns of accessibility are visualized in terms of potential production zones for different types of agricultural and non-timber forest products.This study demonstrates how results from different accessibility measures vary considerably. The mean Euclidean distance to Iquitos is almost 270 km, the mean network distance nearly 760 km and the mean travel time 70 h. Observed network distances from validation points to Iquitos are on average 1.6 times longer than Euclidean distances, and for the whole study area, the average ratio between modeled network distances and Euclidean distances is 3.1. The correlation between network distances and time distances is very strong, but time distances are relatively shorter along the major channels where boat traffic is considerably faster than along narrow, tightly meandering rivers. Measures of boat frequency and transport capacity show that availability of transport possibilities is highly varying across the region. These measures provide insights into the ’thickness’ of trade, indicating the level of market integration for riverine settlements. We conclude that quantifying accessibility in an environment like Peruvian Amazonia requires measures that take into account the spatial structure and dynamic nature of the riverine transportation network. Time as a unit of distance provides the most relevant measure of accessibility in the Amazonian context, where many human actions and traditional livelihoods are controlled by travel times between the regional core and the hinterland. 相似文献
2.
河流碳循环对全球变化的响应与反馈 总被引:10,自引:0,他引:10
河流连接陆地生态系统和海洋两大活动碳库,构成全球碳循环的一个关键环节。河流碳的输出及循环过程与近岸水域环境、海洋碳库变动及全球气候系统紧密相关。有机碳在全球碳循环系统中处于核心地位,了解河流有机碳通量及性质变化是目前河流碳循环研究的重要内容之一。流域面积的大小及气候和环境性质的差异对河流碳的输移及循环过程影响显著。目前,亚洲季风流域尤其是众多的小流域缺乏系统的有关悬移质生源要素的信息。陆地侵蚀-沉积过程控制着河流碳的主要来源和归宿。当前,人类活动主宰着陆地的侵蚀-沉积状况,这在很大程度上表现为加速了陆地生态系统碳库的扰动与再沉积,并加强了河流向海洋的碳输送。 相似文献
3.
Travel behavior of the present generation of youths is being increasingly explored due to their relevance in shaping future accessibility needs and mobility habits. The present study offers an original perspective on this topic by identifying territorial disparities that emerge in youth mobility patterns in rural and urban areas. Unlike most previous research, we propose taking a global view on mobility by analyzing all trip purposes and transportation modes. This is conducted by analyzing a comprehensive mobility survey in the Barcelona Metropolitan Region, which provides data on mobility engagement, trip purposes, modal split, travel times and territorial differences. In general, youngsters account for larger daily travel times than older adults, present a higher attachment to public transportation and walk less on a daily basis. These differences are enhanced in rural territories, where while older adults overcome accessibility issues with higher use of the private vehicle, youngsters are more likely to invest larger travel times on transit. 相似文献
4.
5.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3):122-127
This paper deals with two basic assumptions about migration patterns in Bangladesh. First, it is commonly assumed that poverty and landlessness in rural Bangladesh lead to migration to and settlement in disaster-prone areas along the main rivers or in low-lying areas in the Bay of Bengal. Second, it is also commonly assumed that when people living in these areas experience loss of land, property and income opportunities due to natural disasters, they are forced to seek their livelihood and housing in urban areas. These two assumptions are discussed on the basis of data from a char in Jamuna river and a slum settlement in Dhaka. 相似文献
6.
1978-2012年武陵山区公路通达性演化及其对经济发展的影响 总被引:1,自引:0,他引:1
利用通达性系数和加权平均出行时间,结合GIS网络分析和空间分析方法,探讨了1978-2012年武陵山区64个县(市、区)与武陵山区及其外围38个地级市以上城市之间通达性演化的格局和特征,并分析了2000-2012年武陵山区经济发展格局,采用柯布—道格拉斯生产函数模型,定量模拟了通达性对经济发展的影响。研究发现:1978-2000年,武陵山区通达性系数的稳定性较好,到2012年,通达性系数较小值具有向武陵山区东南部集聚的趋势。1978-2000年武陵山区的经济加权平均出行时间和人口加权出行时间的优劣程度均具有由东向西逐渐下降的“圈层式”布局的特点,到2012年,经济加权平均出行时间和人口加权平均出行时间较小值均具有向武陵山区东南部迁移的趋势,原因在于武陵山区及其外围的东部和南部城市较多且路网发展更为迅速和完善。2000-2012年,武陵山区经济发展格局相对稳定,形成了“东部和西北部强、西南部和中北部弱”的经济发展格局,但经济发展的绝对差距逐步扩大,两极分化的趋势越来越明显。2000-2012年武陵山区通达性的重要程度发生变化,通达性的优劣程度对于GDP的影响明显上升,通达性的改善在整体上较好地促进了武陵山区GDP的增长,对武陵山区经济发展的作用变得越来越重要。同时,通达性改善削弱了第一产业的发展,但对第二产业发展具有逐渐上升的正向影响,对第三产业发展的正向影响显著上升。研究充实了贫困地区交通与经济发展关系的实证和理论,对武陵山区通达性改善与经济发展具有重要的指导意义,可以为相关政策的制定提供参考依据。 相似文献
7.
Jean-Paul Kibambe Lubamba Julien Radoux Pierre Defourny 《International journal of geographical information science》2013,27(5):1005-1022
Accessibility is a key driving factor for economic development, social welfare, resources management, and land use planning. In many studies, modeling accessibility relies on proxy variables such as estimated travel time to selected destinations. In developing countries, estimating the travel time is hindered by scarce information about the transportation network, making it necessary to take into account off-network travel coupled with considerations of multimodal options available within the existing network. This research proposes such a hybrid approach that computes the travel time to selected destinations by optimizing together a fully modeled multimodal network and off-network travel. The model was applied in a region around Kisangani located in northeastern Democratic Republic of the Congo. Travel times to Kisangani from the hybrid approach were found to be in close agreement with field-based information (R 2 = 0.98). The developed approach also proved to better support real-world transportation constraints (such as transfer points between travel modes or barriers) than cost-distance-based travel-time modeling. Demonstration results from the hybrid approach highlight the potential for impact assessment of road construction or rehabilitation, development of secondary towns or markets, and for land use planning in general. 相似文献
8.
乡镇土地利用总体规划对农村居民出行可达性的影响研究 总被引:4,自引:0,他引:4
可达性是反映区域土地利用状况、居民生活质量和社会公平性的重要指标。提出适用于乡镇土地利用总体规划的农村居民出行可达性分析方法以及GIS支持的实现思路,以浙江省临安市太湖源镇土地利用总体规划方案为例,分析规划前后农村居民出行的可达性情况,并评价规划对农村居民出行可达性的影响。 相似文献
9.
Tong Zhang Shaoxuan Dong Zhe Zeng Jing Li 《International journal of geographical information science》2018,32(8):1649-1676
The temporal dimensions of public transit accessibility have recently garnered an increasing amount of interest. However, the existing literature on transit accessibility is heavily based on oversimplified assumptions that transit services operate at deterministic speeds using predetermined timetables. These measurements may overestimate transit accessibility, especially for large metropolitan areas where inter- and intra-modal transfers are frequent. To handle travel time uncertainty, a multi-modal transit accessibility modeling approach is proposed to account for realistic variations in travel time and service reliability. The proposed approach is applied to the mapping of transit accessibility in Shenzhen (China), where transit services exhibit significant travel time variations over space and time. Compared to traditional transit accessibility measures, our method has been demonstrated to better capture intrinsic spatial and temporal accessibility variations with complex multi-modal transit networks. Normal distribution of inter-stop travel times and constant travel speed between GPS sampling points are assumed to simply the computation, which we consider to adjust in future studies to better quantify the dynamics of transit accessibility across space and time. 相似文献
10.
11.
12.
Katherine Klink 《The Professional geographer》1998,50(1):3-13
Vector data are not uncommon in geography, and include examples such as transportation flows, particulate transport, and cartographic distortion. The directional and vector means and variances of these types of data are easily computed using a complex-arithmetic extension of the equations for scalar mean and variance. The January surface wind field over the contiguous United States provides an example with which to compare the information provided by scalar, directional and vector-based statistics. Spatial patterns of the mean and variance of January wind velocity (the wind vector) resemble patterns of wind speeds and directions but are not a simple superposition of the two, and one cannot necessarily infer the nature of the velocity field from separately computed salar and directional statistics. However, scalar and directional means and variances can lend insight into the features contributing to the velocity mean and variance. Scalar, directional, and vector-based analyses thus provide complementary methods with which to examine the spatial patterns of wind, or of any flow field that can be represented as a vector. 相似文献
13.
14.
福建省综合交通可达性格局及其与制造业空间分布的关系分析 总被引:6,自引:3,他引:3
以福建省为研究区域,县(市)为研究单元,采用加权平均旅行时间指标,分析公路(区内与区外联系)、铁路、港口、航空等交通方式及区域综合交通网络的可达性空间格局,探讨各交通网络空间分布的均衡性。选取制造业中的28个行业,从资源集约度角度将其分为资源密集型制造业、劳动密集型制造业、资本密集型制造业,利用平均集中率测量产业集聚度。引入要素禀赋条件、外部性、规模经济、制度政策4个方面13个变量对福建制造业空间分布影响因素进行回归分析。结果表明:福建省路网可达性由沿海中部向四周降低,其中公路区内可达性呈明显的圈层结构,区外可达性为"井"字形分布,铁路、港口和机场形成以福州、厦门—泉州为可达性高值区的马鞍状格局,综合交通网络可达性呈带状分布。不同类型的制造业在空间分布格局上呈现不同的特征,制造业平均集中率高值区呈环状分布,而制造业集中率低值区呈点状分布,与交通可达性的"凹陷区"重合。可达性与制造业空间集聚呈现很强的相关性,并且与不同类型制造业空间集聚相关程度有所差异,与资源密集型制造业空间集聚相关性相对较低。此外,农业丰裕度、自然资源禀赋、知识溢出效应、相对企业规模等其他变量对制造业空间分布也有显著影响。 相似文献
15.
16.
Mongolian herders are transhumant and therefore follow a specific land use pattern. To understand their movements through a case study, we mapped and superimposed their seasonal camps on a vegetation map and a digital elevation model. We also questioned them about the reasons justifying the locations of their camps, and how they use the surrounding land. It appears that vegetation quality may play a role only in summer, whereas topography is a key driver during 3 seasons. In winter, herders seek shelter against cold winds in rugged places exposed to the south, while in spring and summer, they seek flat places. In spring, to have a clear view of their newborns and in summer, to allow wind to reduce the insect discomfort. Moreover, most of the livestock species stay within a certain distance of the camps depending on the season, but which never exceeds 5.1 km. This leads to a land use pattern where livestock is restrained to specific areas according to the season. Interestingly, during the growing season, when plants are most sensitive to defoliation, most livestock is concentrated on 30.92% of the site surface. Such information is important for range scientists working on grazing impacts at large scales. 相似文献
17.
可达性研究的回顾与展望 总被引:84,自引:10,他引:74
可达性是指利用一种特定的交通系统从某一给定区位到达活动地点的便利程度。可达性反映了区域与其他有关地区相接触进行社会经济和技术交流的机会与潜力。本文综合了可达性的主要定量评价方法,并对各种方法的优缺点进行了比较,总结了近期可达性评价方法的进展与动态。随后分别在区域和国家尺度与城市内部尺度上总结了可达性在区域经济发展研究、城市土地利用、社会服务设施提供、城市社会问题等各方面的应用。相对来讲,国内关于可达性的研究尚不丰富。最后,本文阐述了目前可达性研究中的问题,并对未来研究进行了展望。 相似文献
18.
《The Professional geographer》2013,65(1):3-13
Vector data are not uncommon in geography, and include examples such as transportation flows, particulate transport, and cartographic distortion. The directional and vector means and variances of these types of data are easily computed using a complex-arithmetic extension of the equations for scalar mean and variance. The January surface wind field over the contiguous United States provides an example with which to compare the information provided by scalar, directional and vector-based statistics. Spatial patterns of the mean and variance of January wind velocity (the wind vector) resemble patterns of wind speeds and directions but are not a simple superposition of the two, and one cannot necessarily infer the nature of the velocity field from separately computed salar and directional statistics. However, scalar and directional means and variances can lend insight into the features contributing to the velocity mean and variance. Scalar, directional, and vector-based analyses thus provide complementary methods with which to examine the spatial patterns of wind, or of any flow field that can be represented as a vector. 相似文献
19.
20.
Distance is a key variable in explicating environmental, social, and economic conditions and in defining spatial and temporal patterns. Prior research has primarily focused on using simple to complex algorithms for calculating distances along road networks. In contrast, few algorithms are available for distance calculations along fluvial networks which are often more erratic, divergent and transient than road networks. Fluvial transportation is relied upon worldwide, particularly in developing regions, where communities use river networks for transportation, access to natural resources and for trade and commerce. This paper presents a methodology developed for mapping complex fluvial networks for travel distance analysis. The methodology was applied in four major river basins in western Amazonia over some 35,000 km of river length and incorporating 919 communities as origins/destinations. A cost path and network analysis methodology was created using vector and raster datasets in a Geographic Information System (GIS) to assess interactions among communities and the distances traveled by river to reach district capitals, major urban centres and marketplaces. An accuracy assessment using distance values calculated from a previous study using a different methodological approach in the region as well as Google Earth Pro, found a high degree of concordance for distance calculations. Our methodology creates a very flexible approach for complex river systems that can be use to calculate river distances in an adaptive and efficient manner and that can be use in other regions of the world where rural communities must rely on rivers for transportation. 相似文献