期刊文献+
共找到4,695篇文章
< 1 2 235 >
每页显示 20 50 100
The Transformation and Governance of Urban Villages with Historic Culture:A Case Study of Xiaxifang,Yongfeng County,Ji'an City,Jiangxi Province
1
作者 DING Fan 《Journal of Landscape Research》 2018年第5期119-121,127,共4页
The transformation and governance of urban villages with historic culture is faced with difficulties such as lack of attention and large-scale demolition and construction,which is not conducive to the continuation of ... The transformation and governance of urban villages with historic culture is faced with difficulties such as lack of attention and large-scale demolition and construction,which is not conducive to the continuation of urban characteristic culture.Taking Xiaxifang,Yongfeng County,Ji'an City,Jiangxi Province for example,this study explored the transformation and governance of urban villages with historic culture from the perspectives of spatial structure,urban function,infrastructure,ecological environment,and community governance,so as to provide a reference for the research and practice of urban villages with historic culture. 展开更多
关键词 HISTORIC culture urban villagE transformation and GOVERNANCE Xiaxifang urban double repair
下载PDF
Rural Development Transformation and Social Governance from the Perspective of Specialization:A Case Study of Ruiling Village in Guangzhou City,China
2
作者 LIN Yuancheng YANG Ren LI Simeng 《Chinese Geographical Science》 SCIE CSCD 2023年第5期796-812,共17页
The reorganization of the global production network and the increased mobility of urban-rural elements have accelerated the differentiation of rural spaces,resulting in a trend towards specialization in rural areas.Th... The reorganization of the global production network and the increased mobility of urban-rural elements have accelerated the differentiation of rural spaces,resulting in a trend towards specialization in rural areas.This paper focuses on the concept of specialization,and takes a renowned bonsai specialized village in Guangzhou City,China as a typical case to explore its transformation and development process,action logic and coupling mechanism with the social governance.The results show that:1)the development of rural specialization in Ruiling Village is shaped by several key actors,such as local governments,grassroots organizations,villagers,social organizations,policies,markets and infrastructure.The transfer of these key actors and the reconstruction of actor-networks in different stages have an important influence on the transformation and realization of rural development goals.2)Through subjects-driven,organization management and resource connection,social governance supports the specialization of rural industrial organization,operation,technology and mode.The governance structure shifts from decentralization to networking,refinement and integration.A coupling community of social governance and specialization is created by the social governance system of‘local government-grassroots organizationseconomic cooperatives-villagers’,which links industries,industrial chains and cooperatives.3)Social governance integrates into the value chain extension process of rural specialized development with a central,multi-level organizational structure.It promotes the construction of the whole value chain through organizational planning,resource integration and image shaping,thus realizing the value,branding and organization of the industry,as well as the integration of rural sustainable development and governance mechanism.Social governance has a profound impact on the development of rural specialization in terms of subject,structure and mode,and participates in the construction of the whole value chain of rural areas.This paper provides a new perspective for understanding the coupling effect of social governance in the rural development transformation,and promotes the rural sustainable development and governance. 展开更多
关键词 rural specialization rural development transformation social governance rural differentiation actor-network theory(ANT) Ruiling village
下载PDF
A new approach towards the sustainability of urban-rural integration:The development strategy for central villages in the Abbasiya District of Iraq using GIS techniques
3
作者 Ahmed Hussein ALLAWI Haider Mohammed Jawad AL-JAZAERI 《Regional Sustainability》 2023年第1期28-43,共16页
The development of rural areas usually has a positive impact on the urban-rural integration. This study explores an innovative approach to stimulate rural development by proposing qualified villages as central village... The development of rural areas usually has a positive impact on the urban-rural integration. This study explores an innovative approach to stimulate rural development by proposing qualified villages as central villages that can provide basic urban services for their residents and residents of neighboring villages. This approach can contribute to overcoming the various problems that rural areas faced at the social, economic, and environmental levels. It seeks to achieve spatial sustainability of rural areas, representing a new approach by integrating urban development methods to revitalize rural villages. The study analyzed 15 villages belonging to Abbasiya District of AL Kufa City in the Najaf Governorate of Iraq. Based on the GIS techniques and the analysis of urban service indicators(village population, percentage of urban building materials used in villages, distance between village and health centers, distance between village and main roads, nature of economic activity, distance between village and educational institutions, distance between village and drinking water sources, number of communication towers, and distance between village and urban administrative center), this study proposed that Abu Gharb and Albu Ghraib can served as central villages in Abbasiya District in the future. This study establishes a new rural spatial structure to achieve rural sustainable development, improves the development status of rural areas, and provides a theoretical basis for the government and relevant institutions to use urban service indicators, achieving rural sustainable development and formulating relevant development policies in Abbasiya District. 展开更多
关键词 Central villages Spatial reorganization Rural sustainable development urban-rural integration urban service Abbasiya District Iraq
下载PDF
Micro-reconstruction Strategies of Urban Villages in Small Towns from the Perspective of Policy Orientation:A Case Study of Zhuangqian Xiongjia Village,Fengcheng City
4
作者 WU Na FAN Qindan 《Journal of Landscape Research》 2023年第4期41-44,49,共5页
As China’s economy shifts from high-speed development to high-quality development,China’s urbanization also shifts from incremental expansion to stock optimization,providing a new direction for the transformation of... As China’s economy shifts from high-speed development to high-quality development,China’s urbanization also shifts from incremental expansion to stock optimization,providing a new direction for the transformation of urban villages.At present,the reconstruction work office of urban villages in small towns is mainly promoted based on government-led and villager main body in the initial exploration stage.From the perspective of policy orientation,to solve the main problems in urban villages in small towns,Zhuangqian Xiongjia Village,Fengcheng City was taken as an example,and the micro-transformation strategies of urban villages were put forward from the perspective of satisfying the appeals of the government,village committee and villagers,so as to provide some references for the transformation of urban villages in other small towns across the country. 展开更多
关键词 Policy orientation urban village in a small town Micro-transformation strategies
下载PDF
Landscape Upgrading and Transformation of Old Urban Parks from the Perspective of Place Attachment:A Case Study of Nanchang Bayi Park
5
作者 Baoyong LI Yuanqing WEN +1 位作者 Bo PENG Huimin TAN 《Meteorological and Environmental Research》 CAS 2023年第2期28-34,41,共8页
On the basis of combing the relevant theories of place attachment, the planning framework of upgrading and reconstruction of old parks based on place attachment was put forward. Taking Nanchang Bayi Park as an example... On the basis of combing the relevant theories of place attachment, the planning framework of upgrading and reconstruction of old parks based on place attachment was put forward. Taking Nanchang Bayi Park as an example, the methods and key points of landscape improvement and transformation of old urban parks based on place attachment were explained to provide new ways and references for the renewal of old urban parks. 展开更多
关键词 Landscape upgrading and transformation Old urban parks Place attachment
下载PDF
Architecture as a Means of Developing Social Exchange:Learning from a Danish Case Study of Refurbishment and Urban Transformation in a Disadvantaged Housing Area
6
作者 Claus Bech-Danielsen Marie Stender 《Journal of Civil Engineering and Architecture》 2023年第6期265-285,共21页
Disadvantaged housing areas from the postwar period typically consist of relatively monotonous and monofunctional multi-storey blocks and have a separate traffic system rendering the areas isolated enclaves in the urb... Disadvantaged housing areas from the postwar period typically consist of relatively monotonous and monofunctional multi-storey blocks and have a separate traffic system rendering the areas isolated enclaves in the urban fabric.It is argued that this spatial isolation contributes to social isolation,and current refurbishments are therefore aimed at linking the housing areas with the surrounding neighbourhoods to enable social exchange between the residents and people from the surrounding areas.Based on a case study in a Danish social housing area,this paper discusses to what extent architectural development and urban strategic transformations can contribute to enabling social exchange in disadvantaged housing areas.Do neighbours enter the disadvantaged housing area as intended?If so,how does this influence their perception of the housing area?The analysis shows that architectural development and urban transformations are interdependent in establishing a social mix in disadvantaged housing areas.It is argued that refurbishments can reduce the stigma surrounding the housing area and its residents.However,the applicability of such strategies is highly dependent on the local context of the housing area. 展开更多
关键词 Disadvantaged housing areas social housing postwar housing areas transformation REFURBISHMENT urban renewal
下载PDF
A Summary of Research on Urban Village Transformation in China from the Perspective of Architectural Spaces
7
作者 HU Jing SHEN Ying 《Journal of Landscape Research》 2019年第5期70-74,80,共6页
Based on the rational classification and screening of the literature related to the transformation of urban villages in China,this paper studied the research framework of the architectural space field in the study of ... Based on the rational classification and screening of the literature related to the transformation of urban villages in China,this paper studied the research framework of the architectural space field in the study of urban village transformation,and analyzed the research status of architectural spaces and users in the process of urban village transformation,proposed four research contents of urban village transformation,namely,promoting space rights for all types of people to live on an equal footing,paying attention to the renewal and rejuvenation of urban areas,attaching importance to the technical methods of space construction,and ensuring flexible and diverse space construction methods,and summed up the necessity of carrying out research on urban village transformation in the field of architectural space construction. 展开更多
关键词 urban villagE transformation ARCHITECTURAL space construction RESEARCH content RESEARCH RESULT
下载PDF
SUSTAINABLE URBAN-RURAL RELATION IN RAPID URBANIZATION AREAS——Case of Transformation of "Urban Village" in Guangzhou
8
作者 WEI Li-hua YAN Xiao-pei 《Chinese Geographical Science》 SCIE CSCD 2005年第3期212-218,共7页
Many studies have been made concerning the problems, characteristics, formation, transformation measures, etc. of urban village from sociology, urban planning and geography, etc., which have made insightful analysis. ... Many studies have been made concerning the problems, characteristics, formation, transformation measures, etc. of urban village from sociology, urban planning and geography, etc., which have made insightful analysis. However, most of these studies started mainly from the standpoint of the city government, drumming for the landscape-oriented urbanization, namely pulling-down the urban village and constructing the splendid residence or business buildings. The article maintains that the most important thing the city government should do is to pay much attention to the sustainable living of urban villagers, who would lose their main income source, namely, the collective dividend and the family housing rent. The single method of compensation has been proved to be harmful to the villagers’ community, in which some young villagers relying on rent were no longer to do anything but stay at home. On the other hand, considering the floating population has become the main stream of renters in urban villages, the emergence of urban villages was inevitable and would continue to exist in a long time under the socio-economic transition in urban China and globalization. Based on the analysis above, the transformation of urban village should take more concerns on the housing demands of floating population besides compensation for local villagers. Meanwhile, it is necessary to avoid the "landscape-oriented urbanization" without the "peasant-to-citizen" transformation. 展开更多
关键词 城乡二元经济结构 城乡经济联系 城市化 广州市 经济管理 广东
下载PDF
Peri-Urban Transformations in Agricultural Landscapes of Perugia, Italy 被引量:2
9
作者 Marco Vizzari 《Journal of Geographic Information System》 2011年第2期145-152,共8页
Urban fringes represent very complex landscapes because of their proximity and mutual dependency with cities and rural areas. These landscapes may be considered as transition entities characterized by fuzzy boundaries... Urban fringes represent very complex landscapes because of their proximity and mutual dependency with cities and rural areas. These landscapes may be considered as transition entities characterized by fuzzy boundaries. An uncontrolled development of urban sprawl and land use changes in these areas may deter- mine negative impacts on all natural, economic and social components. Thus, urban fringes assume a key-role in modern landscape analysis, planning and management. Landscape analysis of these interfaces, as this study shows, can be effectively supported by GIS spatial modelling. The Settlement Density Index (SDI), developed through GIS spatial analysis techniques, expresses punctually the territorial gradients generated by the presence of settlements and allows the identification of the urban fringes in the two periods under invest-tigation. These areas are then characterized and analyzed quantitatively using detailed land use data. The comparison of the diachronic information highlights the transformations of peri-urban landscapes that appear mainly related to the modifications of spatial configuration of urban areas and to the changes of agricultural systems. 展开更多
关键词 Landscape ANALYSIS Density ANALYSIS urban FRINGES GIS Land Use transformationS MORPHOLOGICAL Spatial Pattern ANALYSIS
下载PDF
Research on the Optimization of Public Spaces in Urban Villages Based on Space Syntax:A Case Study of Luochengtou Village in Handan City 被引量:2
10
作者 CHEN Xiaowei HU Qiyang CAI Qiang 《Journal of Landscape Research》 2021年第6期99-102,共4页
This paper based on the theory of space syntax took Luochengtou Village in Handan City,Hebei Province for example,tried to figure out a proper way for the renewal of urban villages,and change the current dilemma of&qu... This paper based on the theory of space syntax took Luochengtou Village in Handan City,Hebei Province for example,tried to figure out a proper way for the renewal of urban villages,and change the current dilemma of"one-size-fits-all"and"removing all"in most cases,and put forward that local conditions and regional characteristics must be considered to propose the renewal strategies more suitable for the targeted objects.Based on the space syntax Depthmap software and field investigation,the paper analyzed the accessibility,intelligibility and throughput of public spaces in Luochengtou Village,and put forward 3 optimization strategies in view of the problems such as insufficient public spaces,poor accessibility and intelligibility of roads,and poor activity of spaces,specifically,increasing public activity spaces,sorting out public space network,and creating active space nodes,so as to optimize public environment of the village,enhance villagers’sense of belonging,sense of safety and sense of identity. 展开更多
关键词 Space syntax urban village Public space Optimization strategy Luochengtou village
下载PDF
Evolution of Living Space in Traditional Villages in the Pearl River Delta under the Influence of Urbanization:A Case Study of Xiaozhou Village in Guangzhou City 被引量:1
11
作者 Zhong Guoqing 《Journal of Landscape Research》 2021年第5期36-40,共5页
Traditional villages in the Pearl River Delta are known as "Lingnan water village".Urbanization affects the style of traditional villages in three ways.It also presents a positive side under the background o... Traditional villages in the Pearl River Delta are known as "Lingnan water village".Urbanization affects the style of traditional villages in three ways.It also presents a positive side under the background of new urbanization.The living space of Xiaozhou Village has the unique characteristics of Lingnan water village.At the same time,it is obviously affected by urbanization.Industrialization and commercialization continue to promote the villagers to dismantle the old and build new ones until it becomes a village in the city.The evolution of the traditional living space is reflected in three aspects:being nibbled away or even disappeared,destroying the traditional style,function disappearance or transformation.In the later stage of urbanization,some living spaces have been repaired and updated. 展开更多
关键词 urbanIZATION Pearl River Delta Traditional villages Living space EVOLUTION
下载PDF
基于Transformer的城市三角网格语义分割方法
12
作者 资文杰 贾庆仁 +2 位作者 陈浩 李军 景宁 《南京大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第1期18-25,共8页
对城市三角网格(Urban Triangle Mesh)数据进行语义分割以识别不同类别的物体,是理解和分析三维城市场景的一种非常重要的方法.城市三角网格是一种具有丰富空间拓扑关系的三维空间几何数据,包含大量的几何信息,然而,现有的方法仅仅单独... 对城市三角网格(Urban Triangle Mesh)数据进行语义分割以识别不同类别的物体,是理解和分析三维城市场景的一种非常重要的方法.城市三角网格是一种具有丰富空间拓扑关系的三维空间几何数据,包含大量的几何信息,然而,现有的方法仅仅单独对每种几何信息进行特征提取,然后简单地融合再进行语义分割,难以利用几何信息之间的关联性,对个别物体的分割性能不佳.为了解决上述问题,提出一种基于自注意力机制Transformer的模型UMeT(Urban Mesh Transformer),其由多层感知机和MeshiT(Mesh in Transformer)模块构成,不仅可以利用多层感知机提取高维特征,还可以利用MeshiT模块计算各种几何信息之间的关联性,有效挖掘城市三角网格数据中隐含的关联.实验证明,UMeT能提取高维特征,同时保证城市三角网格数据的空间不变性,从而提升了语义分割的准确性. 展开更多
关键词 城市三角网格 语义分割 transformER MESH 自注意力机制
下载PDF
On the Process of Peasant Workers' Transformation to Urban Residents 被引量:1
13
作者 Liu Chuanjiang Dong Yanfang Wang Jing 《Chinese Journal of Population,Resources and Environment》 北大核心 2008年第1期63-71,共9页
The unique two-stage "Chinese path" of China’s ru-ral-urban migration, which cannot be fully explained by classical theories of economic development, makes us to give peasant workers’ transformation to urb... The unique two-stage "Chinese path" of China’s ru-ral-urban migration, which cannot be fully explained by classical theories of economic development, makes us to give peasant workers’ transformation to urban residents a top priority. On the basis of fully explaining peasant workers’ transformation to urban residents, a method for measuring its process has been advanced and then confirmed with the data of March in 2005 from surveys to peasant workers in Wuhan. Finally, the suggestions of acceler-ating peasant workers’ transformation to urban residents to pro-mote the construction of a harmonious society have been drawn from the analysis. 展开更多
关键词 农民 城镇居民 转化过程 农村城市化 小城镇建设 中国
下载PDF
基于轻量级Transformer的城市路网提取方法 被引量:1
14
作者 冯志成 杨杰 陈智超 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第1期40-49,108,共11页
针对现有方法存在道路区域提取不精准和实时性不足的限制,提出基于轻量级Transformer的路网提取方法RoadViT.利用卷积神经网络与Transformer混合的MobileViT架构进行编码特征,有效地提取高级上下文信息.提出金字塔解码器实现多尺度特征... 针对现有方法存在道路区域提取不精准和实时性不足的限制,提出基于轻量级Transformer的路网提取方法RoadViT.利用卷积神经网络与Transformer混合的MobileViT架构进行编码特征,有效地提取高级上下文信息.提出金字塔解码器实现多尺度特征的提取和融合,生成像素类别的概率分布.结合Mosaic与多尺度缩放和随机裁剪策略实现数据增强,构建精细多样的遥感图像.针对城市遥感图像中道路类别和背景类别的不平衡问题,提出动态加权损失函数.实验结果表明,RoadViT的参数量仅为1.25×10^(6),在Jetson TX2上的推理速度可达10帧/s,在CHN6-CUG数据集上的精度可达57.0%.所提方法是轻量级Transformer在城市遥感图像中的有效探索,在保证推理实时性的同时,实现道路提取精度的提升. 展开更多
关键词 城市路网提取 transformER MobileViT 遥感图像语义分割 轻量级模型
下载PDF
Planning,Protection and Construction of Ancient Villages in Jiangxi under the Background of New Urbanization: Taking the Water Management System of Mingkou Village in Leping City,Jiangxi Province as an Example
15
作者 Haoran LENG Zhiyuan BAI Shaomin NI 《Asian Agricultural Research》 2019年第7期34-37,41,共5页
Urbanization is an inevitable trend of economic development. It is an important indicator that reflects the industrialization and modernization of a country. In the long-term urbanization process in China, due to the ... Urbanization is an inevitable trend of economic development. It is an important indicator that reflects the industrialization and modernization of a country. In the long-term urbanization process in China, due to the excessive emphasis on the status of the city and one-sided emphasis on urban development, a serious of urban diseases such as population congestion and environmental damage have been caused. Meanwhile, neglected rural areas have exposed social problems such as aging and hollowing out, making the urban-rural dual structure more prominent. Currently, China s economic and social development has reached a new stage, and the realization of urban-rural integration is a major measure to comprehensively develop the national economy and social undertakings. Vigorously developing the rural areas and revitalizing the countryside has become a national policy. Traditional ancient villages are treasures in the vast rural areas. They should be more protected and developed to eliminate the urban-rural gap, thereby passing down and carrying forward the essence of traditional culture and enhancing China s national confidence and cultural confidence. Focusing on the protection and planning of ancient villages, combined with the current policy background of new urbanization, based on field research on Mingkou Village, Leping City, Jiangxi Province, protective development strategies are put forward for ancient villages and their water management from the perspective of water management in ancient villages to arouse people s attention to the protection of ancient villages. 展开更多
关键词 New urbanIZATION Ancient villagE Mingkou villagE Water management system PLANNING and PROTECTION
下载PDF
Urban structure transformation of Lhasa City after the peaceful liberation and democratic reform of Tibet
16
作者 张樱子 ZHAO Shi-chen Atsushi DEGUCHI 《Journal of Chongqing University》 CAS 2017年第3期124-140,共17页
In Tibet, Buddhism coupled with its theocratic history has given its cities and urban areas unique forms and structures. As the political, religious, and economic center of Tibet, Lhasa City has a special urban form a... In Tibet, Buddhism coupled with its theocratic history has given its cities and urban areas unique forms and structures. As the political, religious, and economic center of Tibet, Lhasa City has a special urban form and has experienced typical urban transformation processes for a thousand years. The city has been experiencing significant urban structure transformation that has accompanied the socio-economic development in recent decades since the peaceful liberation and democratic reform of Tibet during the 1950 s. Hence, this study presents the time-series of urban structure changes in Lhasa City for the purpose of understanding the characteristics and mechanisms of transformation under the republican political system. First, the study illustrates the urban socio-economic changes of Lhasa City beginning in the 1950 s via statistical data analysis. We then divide the urban development into several stages. Subsequently, we identify the transformation characteristics of urban structure by investigating urban growth, street structure, land-use, and religious facilities via maps of the city from every development stage. This paper ultimately discusses the regulation of city transformation. This study clarifies several probable issues facing Tibetan cities and proposes suggestions for future urban development of Tibetan cities. 展开更多
关键词 urban structure transformation highland city Tibetan Buddhism theocratic governance
下载PDF
Survival and Protection of Traditional Chinese Villages in the Context of Urbanization
17
作者 Yan YU 《Asian Agricultural Research》 2017年第4期26-28,共3页
The traditional village is the witness of farming civilization,but also the most important carrier of China's excellent traditional culture. However,in the process of high-speed urbanization,more and more traditio... The traditional village is the witness of farming civilization,but also the most important carrier of China's excellent traditional culture. However,in the process of high-speed urbanization,more and more traditional villages get gradually depressed and have problems of survival crisis. Fully exploring the value of traditional villages and protecting and activating them have attracted wide attention. This paper firstly introduced definition of traditional villages and analyzed the influence of urbanization on traditional Chinese villages. Then,it came up with recommendations for survival of Traditional Chinese villages in the context of urbanization from establishing the protection mechanism,raising the protection awareness,and strengthening dynamic inheritance,to provide some ideas and methods for protection and upgrade of traditional villages. 展开更多
关键词 Traditional village urbanIZATION SURVIVAL PROTECTION Dynamic inheritance
下载PDF
Changes of Villagers' Welfare and Security in the Reconstruction of Urban Villages——A Case of Guangzhou Province,China
18
作者 YU Xue-fei 《Asian Agricultural Research》 2010年第7期10-13,共4页
In the paper,the connotations of welfare are briefly outlined from the broad and narrow aspects and the changes of villagers' welfare ofurban villages in city are analyzed.In economic welfare terms,at the same tim... In the paper,the connotations of welfare are briefly outlined from the broad and narrow aspects and the changes of villagers' welfare ofurban villages in city are analyzed.In economic welfare terms,at the same time of losing their lands,villagers have obtain certain amount of landcompensation after the expropriation of lands.In non-economic welfare terms,the social status,lifestyle,environmental conditions and psychologi-cal state of the reallocated villagers have changed obviously.The status quo of the urban villages is outlined.Besides,the main problems in the ur-ban villages of Guangzhou are probed into,which covering the ubiquitous illegal utilization of lands and illegal construction,poor public order,lowpublic quality,imperfect public facilities and so on.The modes(Liede mode,Pazhou mode,Huadi mode and public self-financing mode) andcharacteristics of reconstructing the urban villages are concluded.The impact of the construction on villagers' welfare is concluded as well as the se-curity system for protecting villagers' welfare in the reconstruction of urban villages.It is suggested that the government and the villages should sharethe expenditures on the education and training of villages and share the input on infrastructure.In addition,the government and the villages shouldtake the responsibilities in terms of public security,culture and so on. 展开更多
关键词 villagers'welfare SECURITY Reconstruction of urban villages Security system China
下载PDF
Effects of phytoplankton community and interaction between environmental variables on nitrogen uptake and transformations in an urban river
19
作者 Jing YANG Haiguang PEI +5 位作者 Junping LÜ Qi LIU Fangru NAN Xudong LIU Shulian XIE Jia FENG 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2022年第3期1012-1026,共15页
Phytoplankton are not only the main bearer of the nitrogen cycle,but also a key link driving nitrogen cycle.However,most phytoplankton cannot directly use N_(2),and they must uptake nitrogenous nutrients(ammonium,nitr... Phytoplankton are not only the main bearer of the nitrogen cycle,but also a key link driving nitrogen cycle.However,most phytoplankton cannot directly use N_(2),and they must uptake nitrogenous nutrients(ammonium,nitrate,and urea)to meet their photosynthesis needs.We examined the uptake characteristics of several nitrogenous substrates using stable isotope technique and identifi ed the potential nitrogen transformations in the Fenhe River.Results revealed that spring phytoplankton community composed of mainly Fragilaria,Ulothrix,Microcystis,and Synedra.Urea can meet the spring partial nitrogen requirement of phytoplankton.The large uptake rate of urea depended on urease,chlorophyll a,and nitrate concentrations as shown in random forest models.Cyanobacteria explained more than 42.8%of the total abundance at all sites in summer.Upstream was dominated by Actinastrum,and Chlorella was relevant in the downstream section.The uptake rates of ammonium were higher than those of nitrate and urea.In addition,the random forest model demonstrated that ammonium,urease,and dissolved oxygen(DO)were the major contributors to the ammonium uptake rates.Ammonium was taken up preferentially in autumn and phytoplankton(Cyclotella,Chlorella,and Pseudanabaena)appeared to be able to respond to changes in nitrogen forms by adjusting their community composition.Structural equation models demonstrated that temperature-induced changes in DO directly affected the transformations of different forms of nitrogen.At the same time,dissolved organic carbon can directly act on nutrients and then indirectly affect enzyme activity.There were great diff erences in the positive and negative effects of different paths in the process of nitrate reduction to nitrite and then reduction to ammonium in time and space.These findings provide a better understanding of the underlying mechanism of nitrogen uptake and the influences of interaction between environmental variables on nitrogen transformations in urban river ecosystems. 展开更多
关键词 PHYTOPLANKTON environmental variables nitrogen uptake transformation urban river
下载PDF
Impact of Urban Land Transformation on Water Bodies in Srinagar City, India
20
作者 Shahab Fazal Arshad Amin 《Journal of Environmental Protection》 2011年第2期142-153,共12页
Human actions rather than natural forces are the source of most contemporary changes in the state and flows of the biosphere. Understanding these actions and the social forces that drive them is crucial to understandi... Human actions rather than natural forces are the source of most contemporary changes in the state and flows of the biosphere. Understanding these actions and the social forces that drive them is crucial to understanding, modelling and predicting local, regional as well as global environmental change and also for managing and responding to such change. The present study investigates the patterns of urban land transformation in Srinagar City, which lies in fragile hill eco-system of Kashmir valley. The results points towards unplanned and haphazard urban expansion and transformation. These transformations have severely destroyed the water bodies both in terms of area as well as its quality. 展开更多
关键词 urban LAND transformation Water BODIES AGRICULTURE Marshy
下载PDF
上一页 1 2 235 下一页 到第
使用帮助 返回顶部