冻融循环作用下路基土回弹模量试验研究   总被引：7，自引：4，他引：3  

王威娜  支喜兰  毛雪松  侯仲杰  雷明轩 《冰川冻土》2010,32(5)

为研究季节冻土地区冻融循环作用对路基土回弹模量的影响,以2种路基土作为研究对象,通过风干和加湿的方法,使高50mm、直径为50mm无侧限圆柱体试件达到5种预期含水率;采用承载板法进行回弹模量试验,分析了路基土在0～12次冻融循环作用下,回弹模量随冻融循环次数变化的规律.结果表明:随着冻融循环次数的增加,土体的回弹模量减小,到第6次冻融循环后土体回弹模量衰减基本稳定.在进行季节冻土地区路面设计时,应考虑冻融循环作用对路基土的影响,建议选取第6次冻融循环后的土体回弹模量作为路基强度设计值.  相似文献   

基于应对公共健康危害的广州社区恢复力评价及空间分异   总被引：4，自引：0，他引：4  

杨莹  林琳  钟志平  欧莹莹  徐茜  蒙美昀  郝珊 《地理学报》2019,74(2):266-284

公共健康危害形势日趋严峻,综合测度社区恢复力并探寻空间分异格局,有利于摸清城市公共健康水平及社区应对健康危害的能力,对推动社区健康治理、促进健康公平具有现实意义,同时对社会—生态系统恢复力研究向公共健康领域拓展及中国化探索具有理论创新意义。以广州市社区为基本单元,从自然环境、建成环境、社会资本、经济资本和政府制度5个子维度选取23个指标、32个表征要素建立应对公共健康危害的社区恢复力评价模型,运用灰色关联TOPSIS法对其进行测度,将社区恢复力划分为优秀、良好、中等、较差和差5个等级,结果显示：恢复力中等水平社区居多,优秀级和差级社区均较少,整体呈“橄榄型”结构,且城市社区恢复力优于乡村社区;社区恢复力空间上由中部向四周,东北部向西部,南部向北部梯度递减,各子系统空间格局差异显著;不同等级恢复力的社区呈“集群化”空间分布,优秀级呈“双中心”格局、良好级呈“核心—边缘”格局、中等和较差级均呈“大分散—小集中”格局、差级呈“边缘延伸”格局;中部、南部公共健康安全,西部相对较危险因而是城市公共健康安全重点防御区域。  相似文献   

Mangrove forests: Resilience,protection from tsunamis,and responses to global climate change   总被引：2，自引：0，他引：2  

Daniel M. Alongi 《Estuarine, Coastal and Shelf Science》2008

This review assesses the degree of resilience of mangrove forests to large, infrequent disturbance (tsunamis) and their role in coastal protection, and to chronic disturbance events (climate change) and the future of mangroves in the face of global change. From a geological perspective, mangroves come and go at considerable speed with the current distribution of forests a legacy of the Holocene, having undergone almost chronic disturbance as a result of fluctuations in sea-level. Mangroves have demonstrated considerable resilience over timescales commensurate with shoreline evolution. This notion is supported by evidence that soil accretion rates in mangrove forests are currently keeping pace with mean sea-level rise. Further support for their resilience comes from patterns of recovery from natural disturbances (storms, hurricanes) which coupled with key life history traits, suggest pioneer-phase characteristics. Stand composition and forest structure are the result of a complex interplay of physiological tolerances and competitive interactions leading to a mosaic of interrupted or arrested succession sequences, in response to physical/chemical gradients and landform changes. The extent to which some or all of these factors come into play depends on the frequency, intensity, size, and duration of the disturbance. Mangroves may in certain circumstances offer limited protection from tsunamis; some models using realistic forest variables suggest significant reduction in tsunami wave flow pressure for forests at least 100 m in width. The magnitude of energy absorption strongly depends on tree density, stem and root diameter, shore slope, bathymetry, spectral characteristics of incident waves, and tidal stage upon entering the forest. The ultimate disturbance, climate change, may lead to a maximum global loss of 10–15% of mangrove forest, but must be considered of secondary importance compared with current average annual rates of 1–2% deforestation. A large reservoir of below-ground nutrients, rapid rates of nutrient flux and microbial decomposition, complex and highly efficient biotic controls, self-design and redundancy of keystone species, and numerous feedbacks, all contribute to mangrove resilience to various types of disturbance.  相似文献   

Relating root causes to local risk conditions: A comparative study of the institutional pathways to small-scale disasters in three urban flood contexts     

《Global Environmental Change》2020

The continued rise of global disaster losses pushes our attention yet further to the causal factors that drive risks, beyond the frame of standardised risk assessment models. A key gap in our understanding of the causality of disasters remains establishing how spatially and temporally distant factors – ‘root causes’ – drive local risk conditions. This is particularly the case for small-scale but high-impact disasters. It includes understanding the role that institutions play in influencing such pathways of risk production. This paper addresses this question using a holistic approach to risk analysis that links past drivers to contemporary conditions. We apply this in three case studies of coastal flood management in urban areas of differential size and integration within the European Union - Rethymno (Crete), Genoa (Italy) and St Maarten (Dutch Caribbean). The paper reveals the importance of local institutions in mediating the impacts of higher-level economic and political changes on local risks. It provides new empirical evidence of the relationship between austerity, institutional reform and local disaster risk reduction. The analysis supports a stronger causal epistemology of resilience to disasters but also leads to re-consideration of the institutional entry points for risk reduction, and the importance of considering context and trade-offs.  相似文献   

Coral bleaching and habitat effects on colonisation of reef fish assemblages: An experimental study     

Saleh A.S. Yahya  Martin Gullström  Marcus C. ÖhmanNarriman S. Jiddawi  Mathias H. AnderssonYunus D. Mgaya  Ulf Lindahl 《Estuarine, Coastal and Shelf Science》2011,94(1):16-23

Degradation and mortality of corals is increasing worldwide and is expected to have significant effects on coral reef fish; hence studies on these effects are essential. In the present study, a field experiment was set up within Mafia Island Marine Park in Tanzania (East Africa) to examine the effects of bleaching and habitat structure on colonisation of coral reef fish assemblages. Live and bleached staghorn coral Acropora formosa was transplanted onto plots in a site dominated by sand and rubble, and the experimental design comprised of three treatments: live coral, bleached coral and eroded coral rubble. There was an immediate increase (within 24 h) in fish abundance and diversity in the two treatments with standing corals. Overall, live and bleached coral plots showed similar effects, but differed from the eroded coral plots which had a much lower abundance and diversity of fish. In general, fish species diversity changed with time over the study period while fish abundance did not. Multivariate analyses showed that while there were differences in fish assemblage structure between standing corals and the eroded coral treatment, there was neither a difference between live and bleached coral treatments nor any temporal effects on fish assemblage structure. Our findings suggest that physical structure and complexity of habitat have stronger effects on colonisation of reef fish assemblages than changes in coral health (such as bleaching) which do not affect coral structure. This may have important implications for appropriate coral reef management.  相似文献   

生计资本对农牧民生活满意度的影响——以甘南高原为例   总被引：16，自引：1，他引：15  

赵雪雁 《地理研究》2011,30(4):687-698

地处青藏高原东缘的甘南高原是典型的生态环境脆弱区,提高农牧民的生计资本成为该区消除贫困、保护环境、可持续利用自然资源的基础与关键.本文建立了生计资本评估指标,结合实地调查资料评估了甘南高原纯牧区、半农半牧区和农区农户的生计资本状况,分析了不同区域农户面临的生活压力及需要的帮助,并采用logistic回归模型分析了农户生...  相似文献   

生计资本与气象可持续减贫          下载免费PDF全文

林霖  陈楠  张德卫 《气象与减灾研究》2018,41(4):310-314

基于英国国际发展署可持续生计分析框架,从农村贫困群体的物质资本、金融资本、人力资本、自然资本和社会资本五个方面,分析了气候变化和气象灾害对农村贫困群体生计资本的影响。建议通过助推贫困群体生计多样化,建立适应气候变化的农村社保体系,建立降低综合灾害风险的应对体系,建立气候变化与贫困减贫的监测评估体系,统筹适应气候变化资金整合渠道,推进气象可持续减贫精准发力。  相似文献   

“结构-能动性”框架下短期经济韧性的动态演化与影响机制——基于新冠肺炎疫情冲击下对东莞企业的访谈     

杜志威  文志敏  金利霞 《热带地理》2022,42(8):1217-1227

2020年初新冠肺炎疫情在全球范围蔓延,对中国中小企业的正常生产和经营造成极大的冲击。在应对疫情冲击的过程中,中国展现了强大的经济韧性,这为研究中小企业经济韧性重塑提供了契机。结构和能动性是影响区域经济韧性的两种因素,但现有研究大多聚焦于结构因素的作用,对于不同经济主体在危机中的能动性则关注较少。通过对东莞市43家中小制造企业的访谈,重点关注新冠肺炎疫情冲击下企业能动主体的响应与行动,运用能动性视角对较短时期内经济韧性的动态演化进行分析,并构建“结构-能动性”的分析框架以揭示影响经济韧性重塑的微观机制。研究发现：经济韧性并不是经济主体与生俱来的固有属性,其形成过程从冲击发生开始先后经历认知―适应―重塑3个阶段;重塑经济韧性是多重因素共同作用的结果,不仅需要个体能动性和集体能动性得到发挥,也受到产业经济、制度安排和基础设施等结构因素的影响。基于揭示能动性因素在塑造短期经济韧性关键作用,总结出3个方面的理论启示：注重短期适应与长期变革的转换;强调能动性对结构因素的塑造;关注能动主体与外部联系的耦合。  相似文献   

基于体制转换的乡村转型时空格局及演变机理——以甘肃省榆中县为例     

石育中  赵琳林  赵雪雁  兰海霞 《地理科学进展》2022,41(12):2311-2326

乡村转型是乡村振兴的关键,也是“三农”转型的重要抓手。论文以黄土高原沟壑区甘肃省榆中县为例,从人口转型、土地转型和产业转型3个维度构建乡村转型指标体系,基于2002—2018年统计数据、农户调研数据、遥感数据等多源数据,运用熵值法、层次分析法、乡村转型度模型和空间分析方法,从县域和农户视角,量化与分析榆中县乡村转型及其时空演变格局,刻画农户生计转型路径;在此基础上,引入体制转换理论阐释乡村转型过程机理,并运用逐步回归分析方法识别驱动乡村转型的关键因素。结果表明：① 2002—2018年榆中县乡村转型度、产业转型度和人口转型度明显上升,而土地转型度稳中有降,乡村转型度和产业转型差异明显且变化较大,在中部川区最为突出。② 乡村转型、人口转型、产业转型均呈现“中部川区较高速和高速转型、北部山区低速转型、南部山区由低速转型向较高速过渡转型的空间格局”,并伴有逐级式和跨级式的变化特点,土地转型空间分布较为分散;乡村转型、人口转型、产业转型和土地转型的热点区主要集聚在中部川区,冷点区主要集聚于北部山区。③ 农户生计表现出多路径转型特征,北部山区为综合型生计转型路径,中部川区和南部山区为兼农型生计转型路径。④ 中部川区实现乡村体制转换,南部山区乡村发展明显升级转型,但未形成新的乡村体制,而北部山区乡村转型不够显著。⑤ 固定资产投资是决定榆中县乡村转型的关键因素。研究结果可为乡村转型提供新的研究视角,也为黄土高原沟壑区乡村振兴与乡村高质量发展提供理论依据。  相似文献   

Research on the Integrated Planning of Blue-Green Space towards Urban-Rural Resilience: Conceptual Framework and Practicable Approach     

YU Qiao  DU Mengjiao  LI Haochen  TANG Xizi  LI Xiaoyan 《资源与生态学报(英文版)》2022,13(3):347-359

Facing the impacts of climate change and the ecological environmental problems caused by urbanization, urban-rural resilience is a new value goal of territorial space development. Blue-green space is an interconnected network system of natural and artificial green space and water bodies, which can dissolve the internal and external pressures of the system by way of mitigatory acceptance and adaptive interaction, reduce the impact of climate change and artificial construction disturbances, and provide diversified composite functions. By recognizing the connotation of the concept of blue-green space, its composite ecological functionality and its relationship with the value of urban-rural resilience, this paper constructs a conceptual framework for the integrated planning of blue-green space in urban and rural areas with “resilient objectives, resource identification, integrated configuration, differentiated regulation”. The paper proposes an integrated and coordinated multi-scale practicable approach of blue-green space planning (i.e., the construction of the blue-green corridor network, the configuration of blue-green open space, the allocation of blue-green infrastructure) and the regulation-based urban-rural transect, with the aim of improving the hydroecological performance and composite functional services in order to realize urban and rural resilience.  相似文献