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多尺度建成环境对居民通勤出行碳排放的影响——来自广州的实证研究 总被引：2，自引：0，他引：2
通勤出行碳排放是城市交通碳排放的主要来源。然而,现有研究很少关注不同地理尺度建成环境对居民通勤出行碳排放的影响差异,且尚未得出一致的结论。本文基于居民出行调查数据和多层次混合效应模型对广州多尺度建成环境对居民通勤出行碳排放的影响进行了实证研究。研究发现：在控制居住自选择效应之后,居民通勤出行碳排放具有明显的空间差异,这些差异是由社区间的建成环境差异所导致的。在不同尺度建成环境中,社区尺度的建成环境对居民通勤出行碳排放的影响最显著。而且,居住地建成环境对通勤出行碳排放的影响比工作地建成环境的影响显著。对建成环境进行规划干预应更多着眼于居民所居住的社区以及与居民日常出行活动联系紧密的社区15分钟步行生活圈。虽然实证案例社区的选取可能存在局限性,但研究结论可为构建低碳城市空间结构、引导居民出行行为转变和制定具有针对性的低碳交通与土地利用政策提供一定的科学理论依据。 相似文献
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基于郑州市地铁1号线、2号线周边11个典型社区的居民调查数据,对地铁开通前后居民通勤交通碳排放进行了核算,从职业、收入和距离等方面分析了地铁沿线居民通勤交通碳排放的影响因素,结果表明:(1)地铁1号线开通后人均通勤碳排放减少18%,地铁2号线开通后减少43%;(2)不同职业类型的居民在地铁开通后通勤碳减排比例由高到低依次为教师、公司职员、其他、工人、公务员;(3)居民收入与通勤交通碳排放量成正相关,与地铁开通后的碳减排比例呈负相关;(4)居民通勤碳减排率与居住地到最近地铁站的距离成负相关,地铁开通后距离地铁站为0~1,1~2,2~3 km的小区人均通勤碳排放减少率分别52.76%,41.12%,24.36%。 相似文献
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北京市不同社区居民通勤行为分析 总被引：4，自引：0，他引：4
近年来北京市社会经济和城市建设取得了重大的成就,但是交通拥堵、居住地和工作地分离、过度通勤等问题也极大地影响了城市的可持续发展,通勤行为研究对理解城市结构、合理规划城市空间布局具有重要作用。以北京市政策性住房、胡同社区、单位社区和商品房四类居住区居民为对象,通过2012年城市居民职住分离抽样调查问卷获取了不同社区居民的居住地和工作地、通勤行为及居住满意度等基本数据,运用统计分析和地理信息系统技术对这些特征进行综合分析,试图理解社会极化加剧背景下不同社区居民通勤行为差异,丰富城市地理研究内容。结果发现:不同社区居民通勤行为存在着显著的差异;四类社区中政策性住房居民平均通勤时间最长为50.4 min(标准差24.7 min),单位社区居民平均通勤时间最短为33.6 min(标准差20.3 min);不同社区居民的通勤工具选择也明显不同,反映出居民社会经济属性差异是通勤行为差异的重要因素。 相似文献
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上海市近郊大型社区居民的通勤特征——以宝山区顾村为例 总被引：3，自引：0，他引：3
《地理研究》2015,(8)
选取位于上海市近郊的宝山区顾村大型社区作为研究对象,采用问卷调查、对比分析、回归分析等方法,分析居民就业以及通勤意愿。在揭示居民总体通勤特征的基础上,比较了购房户、市区拆迁户、农村拆迁户、租房户四类居民群体不同的通勤特征。研究表明:近郊大型社区居民总体上倾向于就近就业,大部分居民实际的通勤时间短于意愿通勤时间中的"可容忍通勤时间",总体上通勤满意度较高。但不同居民群体的通勤特征存在较大差异。利用通勤距离回归模型及通勤满意度逻辑斯谛回归模型的计算表明:居民通勤距离跟收入、受教育程度、户口类型、家庭规模等因素有一定的关联性,而居民对通勤的满意度除了跟收入相关以外,还受通勤距离及通勤意愿的影响。 相似文献
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城市化发展过程中,从微观机制探讨城市空间结构、居民出行行为和碳排放的关系是城市地理学研究的一个重要方面。利用2011年乌鲁木齐居民出行日志调查数据,在分析居民基本出行特征和通勤空间特征的基础之上,探讨了不同城市空间的居民出行碳排放的分布特征和影响因素。结果表明:①乌鲁木齐市居民出行以通勤类出行为主,居民出行在空间上存在差异性,内城中心区和郊区卫星城人均出行次数高于其他区域。城市南、北发展不平衡对郊区居民出行产生影响。②乌鲁木齐市居民通勤的实际平均出行距离为4.9 km,相比于东部大城市具有通勤距离短而通勤时间长的特征。通勤距离在空间上呈现明显的由内向外递增趋势。③2011年乌鲁木齐市居民日常出行人均直接碳排放量为682.95 g,居民日常出行碳排放表现为中心区和卫星城的低碳化、近郊区居民中碳化和远郊区居民的高碳化。 相似文献
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基于结构方程模型的西宁城市居民通勤行为及其影响因素 总被引：3，自引：1，他引：2
近年来,中国城市转型中居民职住关系的变化对通勤交通方式、通勤时间的影响,以及不同居住区居民通勤行为的差异性,引起了学者们的广泛关注。基于2013年西宁市居民活动日志调查数据,分析西宁居民通勤行为的居住区差异,利用结构方程模型分析通勤距离、通勤交通方式、通勤时间三者之间的关系,探讨居住区类型及个人社会经济属性因素对于通勤行为的影响。研究发现,通勤距离对通勤交通方式、通勤时间有显著的正向影响;男性、自有房者、高收入者、兼职就业者、高学历者采用机动化通勤方式的比例较高;在控制个人社会经济属性之后,居住区类型属性仍然对居民通勤行为产生显著影响。基于以上发现,对西宁城市交通发展和空间布局提出政策建议。 相似文献
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通勤时间、社区活动对社区社会资本的影响：基于北京26个社区的调查研究 总被引：1，自引：0，他引：1
城市扩张和郊区化显著增加居民的通勤时间,减少居民在社区内及周边开展的日常活动,进而可能对居民的社区社会资本产生消极影响。基于2017年北京市26个社区居民的社区融合与活动日志问卷调查数据,通过构建结构方程模型,探讨通勤时间、社区活动对社区社会资本的影响机制。结果发现,控制居民社会经济属性和社区区位后,长时间通勤会减少居民在社区及周边1 000 m范围内开展的活动,并进一步对社区社交网络结构、社会信任和共同价值等社区社会资本的不同维度产生负面影响。此外,社区活动中社交娱乐活动的中介效应显著,而个人和家庭事务活动中介效应不显著。最后,证实了促进职住平衡、减少职住分离的规划政策对于增加居民社区活动及培育社区社会资本的重要意义。 相似文献
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基于智慧交通的可达性与交通出行碳排放——理论与实证 总被引：2，自引：2，他引：0
信息与通信技术的发展推动了智慧交通建设,并将进一步提高城市交通可达性和影响居民出行。在全球应对气候变化、减少碳排放的共识背景下,由于"智慧交通—可达性—出行行为(碳排放)"间复杂的影响作用机制,已有的研究难以判断智慧化背景下的城市交通可达性提高将增加抑或减少出行碳排放。如何通过提高城市交通可达性来缓解交通拥堵,保障城市交通运输系统的有效运行,并提高居民出行效率,减少出行碳排放是当前中国智慧交通发展面临的关键问题之一。针对以上科学问题,本文尝试提出基于智慧交通的可达性与交通出行碳排放的理论框架,并以广州为研究案例地,研究了社区居民通勤碳排放特征及其影响机理,社区出行低碳指数格局及其影响因素的空间异质性,以及基于碳排放—位置分配模型的公共中心规划支持系统设计与应用,可为今后的相关研究提供借鉴。 相似文献
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通过优化社区建成环境来优化通勤行为是缓解大城市交通压力的重要举措,实施差异化的社区建成环境政策可能更有助于优化通勤行为。在利用手机信令数据构建居委会之间的职住联系OD数据库并计算居委会的居民平均通勤距离的基础上,构建社区建成环境“5D”指标体系,利用地理加权回归模型（GWR）来分析社区建成环境对居民通勤距离的影响。研究表明,包括密度、多样性、通达性、距离等维度的多项指标对居民平均通勤距离有显著影响。人口密度提高能减少居民平均通勤距离,但区域差异明显,人口密度较高的城郊村居民承受着长距离通勤。混合的土地利用能减少居民平均通勤距离,尤其是减少郊区居民平均通勤距离。地铁通达性在一定程度上增加了区域居民平均通勤距离。通过调控改善中心城区与郊区的居住成本差异,增加中心城区局部功能相对单一区域和郊区的土地利用混合度,增加中心城区局部区域轨道交通建设力度,皆有利于优化居民通勤行为和减少区域通勤距离。 相似文献
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The movement of bedload over a cross-section is often sampled using a “pressure-difference bedload sampler”, such as the Helley–Smith. Whereas several types are in use, no one device has gained universal acceptance as the standard for use in all types of streams. Moreover, evidence suggests that similar devices may collect substantially different amounts of bedload because of only slight modifications in design. In this study, sample weights collected by three types of pressure-difference samplers are compared to determine whether differences are statistically significant or whether sampler performance is so irregular and overlapping that one might regard them as being the same. The results confirm that the weights of samples collected by the devices are significantly different. Generally, the US BLH 84 collected less material, the Sheetmetal Helley–Smith collected more material, and the Original Helley–Smith was intermediate; these tendencies were consistent at two sites where bedload was measured. The implication of these results is that measured transport rates will vary depending on the sampler used and, therefore, they are not directly comparable without some mode of calibration. To place this finding in a larger context, sediment rating curves, determined from weights of samples and measurements of flow, were integrated over available flow records and used to estimate annual yield. Three estimates of annual yield, one for each device, were then compared with measures of annual accumulation from a weir pond below one of the collection sites. The results indicate that despite differences between the devices, data obtained with pressure-difference samplers estimated annual accumulations of sediment reasonably well. Predicted accumulations were within 40–50% of the measured yield for two samplers whereas the third sampler predicted within 80%. 相似文献
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Natalya N. Davydova Dmitry A. Subetto Valentina I. Khomutova Tatyana V. Sapelko 《Journal of Paleolimnology》2001,26(1):37-51
The vegetation history and development of three different types of lakes, lakes Valday, Kubenskoye and Vishnevskoye (northwest of the East European Plain) were reconstructed using paleolimnological techniques. Watershed vegetation demonstrates a close connection with climate fluctuations: gradual expansion of the southern broad-leaved trees to the North during the Holocene with the maximum extent during the climate optimum (8000–5000 BP); and their subsequent retreat afterwards; followed by the extension of spruce during the cold and dry Subboreal time; and dominance of pine-spruce-birch forests in the Subatlantic time. The Late Pleistocene and Holocene climate changes resulted in lake-level fluctuations and other ecosystem changes. Valday Lake was formed ca. 12,500 BP as an oligotrophic, deep water basin. The lake level decreased during the dry Boreal, then increased again during the humid Atlantic period. The large shallow Kubenskoye Lake was formerly a part of an ice margin lake, which was then separated (ca. 13,000 BP) and developed into the Sukhona Basin with an outflow to the northwest. During the Atlantic, the outflow direction changed to the east. As a result, the ancient Sukhona Lake disappeared and Kubenskoye Lake formed in its modern size and shape. Vishnevskoye Lake, on the Karelian Isthmus, was formed at the beginning of the Preboreal after the disappearance of the Baltic Ice Lake. It was flooded by waters of the Boreal Ancylus transgression of the Baltic Basin and had become a small eutrophic lake by the time. 相似文献
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Andrew K. Skidmore Alison Gauld Paul Walker 《International journal of geographical information science》2013,27(4):441-454
Abstract In this paper, we compare three techniques for mapping wildlife habitat, termed BIOCLIM, CART and a new classification method based on nonparametric techniques. These techniques model dependent map layers of species distributions, where the areas to be mapped are large and the plot data is sparse. The techniques recognise pattern in the (independent) plot data, available to natural resource managers. In this case, the independent data set comprised 12 climate surfaces, that attempt to represent the range of temperature and precipitation important in determining the habitat of kangaroos across Australia. With this particular data set, the CART (decision tree) model was most accurate, but more time consuming to initialise. The relative performance of these models depends on the quality of the data set, and skill of the GIS analyst. Where possible, GIS analysts should implement all available methods, and compare output. 相似文献
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The tree species Populus euphratica, the shrub Tamarix ramosissima and the sub-shrub Alhagi sparsifolia are phreatophytes that grow along the southern fringe of the Taklamakan Desert (NW China). We hypothesised that in the shoot xylem of these species, the fraction of conduits with a large cross-sectional area and the hydraulic conductivity decrease in the sequence A. sparsifolia > T. ramosissima > P. euphratica according to the different ground water distances at the typical sites of the species’ occurrence. The theoretical hydraulic conductivity related to the total cross-sectional xylem area (kttot) or to the cross-sectional area of the conduits (ktcond) was computed using a modified Hagen-Poiseuille equation. The percentage of wide conduits and ktcond were highest in A. sparsifolia, and smallest, in P. euphratica. With regard to kttot, the diffuse-porous to semi-ring-porous P. euphratica occupied an intermediate position due to an increased percentage of conducting area related to the total cross-sectional xylem area. This figure as well as kttot were lowest in the semi-ring-porous to ring-porous T. ramosissima. The kttot values corresponded to the leaf area-related hydraulic conductivity calculated from measurements in the field. Altogether, our results match the typical occurrence of the species with respect to the ground water depth. 相似文献
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Water is well established as a major driver of the geomorphic change that eventually reduces mountains to lower relief landscapes. Nonetheless, within the altitudinal limits of continuous vegetation in humid climates, water is also an essential factor in slope stability. In this paper, we present results from field experiments to determine infiltration rates at forested sites in the Andes Mountains (Ecuador), the southern Appalachian Mountains (USA), and the Luquillo Mountains (Puerto Rico). Using a portable rainfall simulator–infiltrometer (all three areas), and a single ring infiltrometer (Andes), we determined infiltration rates, even on steep slopes. Based on these results, we examine the spatial variability of infiltration, the relationship of rainfall runoff and infiltration to landscape position, the influence of vegetation on infiltration rates on slopes, and the implications of this research for better understanding erosional processes and landscape change.Infiltration rates ranged from 6 to 206 mm/h on lower slopes of the Andes, 16 to 117 mm/h in the southern Appalachians, and 0 to 106 mm/h in the Luquillo Mountains. These rates exceed those of most natural rain events, confirming that surface runoff is rare in montane forests with deep soil/regolith mantles. On well-drained forested slopes and ridges, apparent steady-state infiltration may be controlled by the near-surface downslope movement of infiltrated water rather than by characteristics of the full vertical soil profile. With only two exceptions, the local variability of infiltration rates at the scale of 10° m overpowered other expected spatial relationships between infiltration, vegetation type, slope position, and soil factors. One exception was the significant difference between infiltration rates on alluvial versus upland soils in the Andean study area. The other exception was the significant difference between infiltration rates in topographic coves compared to other slope positions in the tabonuco forest of one watershed in the Luquillo Mountains. Our research provides additional evidence of the ability of forests and forest soils to preserve geomorphic features from denudation by surface erosion, documents the importance of subsurface flow in mountain forests, and supports the need for caution in extrapolating infiltration rates. 相似文献
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根系生物量是准确评估森林生态系统碳储量及碳汇功能的一个重要数据。采用标准木全收获法研究了新疆3种主要森林树种根系生物量,并分析了其在垂直梯度上的分配规律和随年龄的变化特点。结果表明：（1）新疆杨、西伯利亚落叶松和阿勒泰冷杉根系总生物量分别为43.409、42.152 t/hm2和16.19 t/hm2;（2）根系生物量随土壤深度增加迅速减少,约88.37%以上的根系生物量集中分布在0～40 cm土层中,在超过40 cm土层中,根系生物量降至较低水平（约为8.3%）;（3）随林分年龄的增长,各林分根系总生物量呈递增趋势,在中龄林根系生物量增长速率达到最大。各级根系中粗根、中根及细根生物量随年龄的增长所占比例呈现递减规律,而其根桩和毛细根生物量差异较大,所占比例随年龄的增大基本呈增大趋势;（4）在表层土壤中各林分在林木的幼龄及中龄阶段根系生物量都处于较高比例,之后呈下降趋势后维持在一定水平基本不变,而深层土壤中各林分在幼龄阶段都处于一个较低的水平,后以一定比例逐渐增长;（5）新疆杨、西伯利亚落叶松和阿勒泰冷杉根系年平均生产力分别为：1.070 8 t·hm-2·a-1、1.014 4 t·hm-2·a-1和0.910 7 t·hm-2·a-1。 相似文献
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风沙活动强度3种估算指标对比及适用性分析 总被引：1，自引：1，他引：0
风沙活动强度是风沙地区交通、能源基地等基础设施建设和运营中科学开展风沙工程防护设计须考虑的重要内容。但在实际工作中尚缺乏操作性强、适用性广的风沙活动强度估算指标。本研究选取风蚀气候侵蚀力、沙丘活化指数和输沙势3种常用指标,基于中国北方风沙区多个具体工程案例,对比分析了3种指标的适宜性及存在问题。结果表明：（1）由于没有考虑工程周边沙源丰富程度的相关影响因素（如植被、戈壁砾石的覆盖度）,3种指标的估算结果均难以准确客观地反映具体工程的实际风沙问题。（2）采用高精度风速风向数据计算的输沙势更能表达干旱地区的风沙活动特征,但在降水较多的区域偏差较大。（3）铁路等线性工程两侧风沙活动强度可能存在差异,相同防沙措施的防护效益存在明显差别,具体工程风沙活动强度的估算应明确其方向性差异。在指导防护体系建设时,需尽可能考虑降水、气温、风速、风向等多种因子,同时结合沙源、地表覆盖度、工程走向等实际情况来分析风沙活动强度差异。研究结果有助于提出一种准确度高、适用性广、可操作性强的风沙活动强度估算指标,为有效开展防沙工程设计提供指导。 相似文献