芦苇形态结构对黄河三角洲不同生境的响应   总被引：2，自引：0，他引：2  

韩鹏  吴耿  吴勇泉  项俊  余龙江 《湿地科学》2011,9(2):185-190

植物的形态结构总是与环境相适应。采用光学显微技术和环境扫描电镜技术对黄河三角洲新生湿地河口区和内陆区两种生境下芦苇(Phragmites australis)根解剖结构、叶片解剖和超微结构进行了对比分析。研究结果表明,芦苇叶片和根的形态结构与生态环境有关;两种生境下,芦苇叶片上表皮均有明显泡状细胞群分布,芦苇上下表皮均有气孔分布,且下陷;在河口区,芦苇叶片维管束鞘细胞近上表皮处有较大程度延伸,下表皮处常延伸至近表皮,呈开放状态,叶片表面常有蜡质覆盖;在内陆区,芦苇叶片维管束鞘细胞较大,有的为两层;此外,河口区芦苇根的中皮层细胞分化为明显的通气组织,内皮层凯氏带明显,而内陆区芦苇根的中皮层细胞排列规则,呈辐射状。芦苇在适应不同生境时其形态结构所发生的变化是不同的。叶片维管束鞘细胞的延伸、表皮被蜡质和根中通气组织、凯氏带等结构是芦苇适应河口区盐胁迫的结果;而叶片维管束鞘细胞增大、细胞层数增加和根的中皮层细胞辐射状排列是芦苇适应干旱胁迫的结果。  相似文献   

The impacts of permafrost change on NPP and implications: A case of the source regions of Yangtze and Yellow Rivers     

Yiping Fang  Dahe Qin  Yongjian Ding  Jianping Yang  Keyan Xu 《山地科学学报》2011,8(3):437-447

This paper studies the relationship between net primary productivity (NPP) and annual average air temperature (GT) at 0cm above ground in permafrost regions by using revised Chikugo NPP model,cubic spline interpolating functions,and non-linear regression methods.The source regions of the Yangtze and Yellow Rivers were selected as the research areas.Results illustrate that:(1) There is significant non-linear relationship between NPP and GT in various typical years;(2) The maximum value of NPP is 6.17,5.87,7....  相似文献   

Adaptive finite element analysis of mode I fracture in cement‐based materials     

M. V. K. V. Prasad  C. S. Krishnamoorthy 《国际地质力学数值与分析法杂志》2001,25(11):1131-1147

Microscopic studies using advanced experimental techniques have provided better insight into the fracture mechanisms in cement‐based materials. A clear understanding of fracture mechanisms is critical for the development of rigorous computational models for analysing fracture. Fracture analysis is usually carried out by finite element method. Accuracy of FE analysis depends upon the choice of mesh and for the predictions to be reliable, discretization errors are to be minimized. In cohesive crack approach, the non‐linearity is limited to the boundary conditions along the geometric discontinuity while the bulk of the material retains its elastic nature. The paper presents a mesh‐adaptive strategy based on ZZ error estimator to model discrete crack propagation in cement‐based materials. Examples of simulations have demonstrated the potential of the mesh‐adaptive technique in modelling the evolution of the localized strain profiles as well as failure of concrete test specimen. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

基于GIS的赤水市金钗石斛农业气候区划   总被引：4，自引：0，他引：4  

罗天虎 《河南气象》2014,(2):70-73

石斛是热带、亚热带丛生植物,喜温暖湿润气候。赤水市是我国目前金钗石斛最大和最适宜种植区。根据赤水市气候资源特点及金钗石斛适宜生长环境指标,选取了年平均气温、全年≥10℃活动积温、海拔高度、月平均气温≥25.0℃月数、分蘖开花期(3-5月)空气相对湿度等5个气象因子作为种植区划指标,在综合考虑经度、纬度和海拔高度对气候资源影响的基础上,利用遵义市12个气象站1971-2000年气候资料和台站信息,采用逐步回归法分别构建了4个区划因子的细网格推算模型。基于数字高程(DEM)数据推算了分辨率为1 km的赤水市气候资源数据集。利用赋值法对5个区划指标分别计算,按照适宜种植区、次适宜种植区和不适宜种植区3个等级完成了赤水市金钗石斛种植气候区划。区划结果显示,赤水市金钗石斛的适宜种植区随地形和海拔高度而变化,主要分布在沿赤水河两岸和沿习水河两岸的沟谷或山地。次适宜和不适宜区主要分布在海拔700 m以上的半高山地区,冬季气温偏低、热量供应不足和夏秋干旱是这些区域不适宜种植的主要原因。  相似文献   

地震信息网自适应网络安全技术模型研究   总被引：1，自引：0，他引：1  

刘云华  刘治  单新建  李卫东 《地震研究》2011,34(1):96-101

对地震信息网存在的一些安全隐患做了初步调研,在此基础上,提出了自适应网络安全模型及法规、技术和管理三种因素相互配合的防御体系,使网络安全以合理代价控制在可以接受的范围内.  相似文献   

乌鲁木齐河流域普通民众对冰冻圈变化的感知及适应性对策选择   总被引：3，自引：0，他引：3       下载免费PDF全文

邓茂芝  张洪广  毛炜峄  王英巍 《气候变化研究进展》2011,7(1):65-72

基于乌鲁木齐河流域普通民众对气候变化及冰冻圈变化感知情况的问卷调查,结合有关监测研究结果,分析了普通民众对流域气候变化及冰冻圈变化的感知情况,探讨了环境变化对流域水资源和农业生产的可能影响.普通民众对气候变化和冰冻圈变化的感知基本与科学监测事实相符.对气候变化和冰冻圈变化条件下普通民众对水资源紧缺的适应措施的分析发现:...  相似文献   

Alleviating barriers to urban climate change adaptation through international cooperation     

《Global Environmental Change》2014

International cooperation on climate change adaptation is regarded as one of the major avenues to reduce vulnerability in developing countries. Nevertheless, it remains unclear which design properties of international arrangements match with specific problems in local adaptation processes. This paper analyses conditions and institutional design options under which international cooperation can facilitate climate adaptation in urban areas in developing countries. We conduct a qualitative meta-analysis of empirical evidence from 23 cases. Using the archetype approach, we identify re-appearing barriers and change factors in urban squatter settlements and municipal public sectors in developing countries. We characterise five generic modes of international cooperation for climate adaptation based on UNFCCC documents, process observation, and literature review. Combining these analyses, we develop testable propositions that explain how specific design options of international arrangements can alleviate barriers and make use of change factors for urban adaptation in developing countries. We find, first, that international cooperation has the most potential to tackle adaptation barriers in squatter settlements if its institutional mechanisms support improvements of procedures and rights in localised state–society interactions. Second, national or regional centres of competence may foster endogenous dynamics in municipal public sectors. Third, national adaptation policies can enable and incentivise municipal adaptation. Fourth, flexible indicators of adaptation benefits are instruments to tailor international decision making and monitoring systems to local needs. We conclude that these insights, the archetypes approach, and a multi-level study design can be used to advance research on international cooperation, barriers, and success factors for climate change adaptation.  相似文献   

Divergent adaptation to climate variability: A case study of pastoral and agricultural societies in Niger     

《Global Environmental Change》2014

Adaptation is a complex, dynamic, and sometimes unequal process. Stemming from social ecological systems theories of climate change adaptation and adaptive capacity, this case study introduces the concept of ‘divergent’ adaptation. Adaptation is divergent when one user or group's adaptation causes a subsequent reduction in another user or group's adaptive capacity in the same ecosystem. Using the example of pastoral and agricultural groups in northern and southern rainfall zones of Niger, this study illustrates the concept of divergent adaptation by identifying changes to the adaptive capacity of users who are currently engaged in conflicts over access to natural resources. Similar to other studies, we find that expansion of farmland and the consequent loss of pastoral space are restricting pastoral adaptation. Divergent adaptations favoring agricultural livelihoods include cultivating near or around pastoral wells or within pastoral corridors, both of which limit the mobility and entitlements of pastoralists. Institutions rarely secure pastoral routes and access to water points, a problem that is compounded by conflicting modes of governance, low accountability, and corruption. The case study illustrates the need to enhance the adaptive capacity of multiple user groups to reduce conflict, enhance human security, and promote overall resilience.  相似文献   

Scenario Analysis on the Adaptation of Different Maize Varieties to Future Climate Change in Northeast China          下载免费PDF全文

XU Yanhong  GUO Jianping  ZHAO Junfang  MU Jia 《Acta Meteorologica Sinica》2014,28(3):469-480

Based on gridded meteorological data for the period 1981–2100 from the RegCM3 regional model, the changing trends of climatic resources in Northeast China are analyzed, and the distributions of maize varieties are accordingly adjusted. In order to explore the effects of different adaptation countermeasures on climatic productivity and meteorological suitability in the future, maize cultivars with resistance to high temperatures and/or drought are selected. The results show that, in the future, there is likely to be a significant increase in thermal resources, and potential atmospheric evaporation will increase correspondingly.Meanwhile, radiation is predicted to increase significantly during 2041–2070 in the growing season. However, changes in precipitation are unlikely to be sufficient enough to offset the intensification in atmospheric evaporation caused by the temperature increase. Water resources and high temperatures are found to be the two major factors constraining grain yield. The results also show that the warming climate will be favorable for maize production where thermal resources are already limited, such as in central and northern Heilongjiang Province and eastern Jilin Province; while in areas that are already relatively warm, such as Liaoning Province, climatic productivity will be reduced. The climatic productivity and the meteorological suitability of maize are found to improve when the planting of resistant varieties is modeled. The utilization of agricultural climatic resources through the adaptation countermeasures of maize varieties is to increase obviously with time. Specifically, maize with drought-resistant properties will have a marked influence on meteorological suitability during 2011–2070, with suitable areas expanding. During 2071–2100, those maize varieties with their upper limit of optimum temperature and maximum temperature increased by 2℃, or water requirement reduced to 94%, or upper limit of optimum temperature and maximum temperature increased by 1℃ and water requirement reduced to 98%, all exhibit significant differences in climatic potential productivity, compared to the present-day varieties. The meteorological suitability of maize is predicted to increase in some parts of Heilongjiang Provine, with the eastern boundary of the "unavailable" area shifting westward.  相似文献   

Assessing vulnerability to climate change and socioeconomic stressors in the Reef Islands group,Solomon Islands     

Thomas Birk 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):59-75

This article assesses the vulnerability to climatic and socioeconomic stresses in the Reef Islands, Solomon Islands, an atoll island group in the Southwest Pacific. Climate change and the associated sea-level rise are often seen as the most pressing challenges to atoll communities, yet this study aims at critically re-assessing this view by placing climate in the context of a range of other internal and external stressors affecting local livelihoods, including population growth, inadequate land use practices, and lack of economic potential, as well as external factors such as poorly developed infrastructure, economic marginalization and weak governance of Solomon Islands. Findings suggest that some of these non-climatic stresses are currently – and in the short term – more important determinants of local vulnerability than climate change and sea-level rise. Certainly, these stresses are likely to be exacerbated by different elements of climate change in the short, medium and long term, but generally speaking climate change does not appear to be a major driver of the current changes in the islands. On the basis of these observations, the possible adaptation options, relevant to different time scales, are discussed.  相似文献