Wenze Yue

Polycentric Urban Development: The Case of Hangzhou

Despite the advantages of polycentric structure and its rich literature drawn from cities in industialized countries, little attention has been paid to the study of polycentric urban development in developing countries based on land-use information. With Hangzhou used as a case study, the authors investigate polycentric urban development through an analysis of directions of urban expansion, urban–rural gradients, and growth types. The multidisciplinary methodology employed, based on theories and methods in remote sensing, geographic information systems, and landscape ecology, has been proved to be useful in the morphological study of polycentric urban development. It was found that Hangzhou has expanded in different directions at various speeds, shifting to a polycentric urban pattern through radial expansion. Along the main transportation corridors, the values of the mean patch sizes of urban patches displayed multiple peaks, and the landscape-shape index maintained a horizontal trend in urban fringes, reflecting the formation of polycentricity. Further, as edge growth and spontaneous growth accounted for 40%–50% and 30–40% of urban growth, respectively, and infill growth was responsible for only a small proportion of urban growth, it is suggested that dispersed urban patches have been increasingly agglomerated into big ones, especially along road corridors. Hangzhous polycentric urban development was shaped both by the planning efforts of the government and by market forces. The municipal government guided the polycentric development through drafting and revising master plans, annexing nearby districts, and establishing development zones. Nevertheless, market forces played an increasingly important role in Hangzhous polycentric development through the implementation of an urban land market, the inflow of migrant workers, and the relocation of industries.

Spatial determinants of urban land conversion in large Chinese cities: a case of Hangzhou

In this research we assessed the urban land conversion, and identified the factors responsible for the conversion, from 1995 to 2009 in Hangzhou, a large city located in the lower Yangtze River Delta of China. We mapped urban land from satellite images by using a hybrid approach of spectral mixture analysis, unsupervised classification, and expert rules. We employed binary logistic regression to model the probability of urban land conversion as a function of spatial independent variables. In recent years Hangzhou started its transformation from a compact, monocentric city to a polycentric city. We found that accessibility to the central business district, industrial centers, roads, Qiantang River, the amount of built-up area in the neighborhood, locations of markets, and spatial policies were the major determinants of Hangzhous urban land conversion. Moreover, the availability of land in the neighborhood has become increasingly important in recent years. We identified several major institutional forces underlying Hangzhous urban development: administrative annexation and development zones, the increasingly important role of the market, and the unique role of local government. The results from our research indicate the need for policies and plans that can better manage and reduce urban sprawl in Hangzhou.

Assessing spatial pattern of urban thermal environment in Shanghai, China

The aggravating urban thermal environment has considerable adverse effects on urban physical environment, energy consumption, and public health. Due to the complexity of factors contributing to the urban thermal environment, traditional statistical methods are insufficient for acquiring data and analyzing the impacts of human activities on the thermal environment, especially for identifying dominant factors. Based on thermal remote sensing imageries and Geographic Information System analysis, we assessed spatial pattern of urban thermal environment in Shanghai in 2008, and analyzed the factors contributing to the generation of urban heat island (UHI) using principal component analysis (PCA). We found that Shanghai had obvious UHI with uneven spatial pattern in 2008. Further, we identified three most important components leading to the variances of Shanghai’s UHI: the gradient from man-made to natural land cover, landscape configuration, and anthropogenic heat release. A linear model has thus been successfully constructed, implying that PCA is helpful in identifying major contributors to UHI. The findings are of significance for policy implication to urban thermal environment mitigation.

Economic development, urban expansion, and sustainable development in Shanghai

Studies of urbanization effects in Chinese cities from the aspect of the coupled development of economy and environment are rare due to data limitations. This paper studied Shanghai’s fast urban expansion and examined the dynamic relationship between economic growth and environment consequences at the district level. We extracted data on urban built-up area and land surface temperature from remote sensing images. We analyzed the patterns of urban expansion and land use change and explained the dynamic relationship between economic development and environment conditions. We attributed the uneven economic development and environmental change in districts of Shanghai to four main institutional factors: (1) the role of the government, (2) the multi-level urban planning system, (3) land market reform, and (4) the economic restructuring.

Storage and density of soil organic carbon in urban topsoil of hilly cities: A case study of Chongqing Municipality of China

Rapid urbanization results in the conversion of natural soil to urban soil, and consequently, the storage and density of the soil carbon pools change. Taking Chongqing Municipality of China as a study case, this investigation attempts to better understand soil carbon pools in hilly cities. First, the vegetated areas in the study area were derived from QuickBird images. Then, topsoil data from 220 soil samples (0–20 cm) in the vegetated areas were collected and their soil organic carbon (SOC) densities were analyzed. Using the Kriging interpolation method, the spatial pattern of SOC was estimated. The results show that the SOC density exhibited high spatial variability in the urban topsoil of Chongqing. First, the SOC density in topsoil decreased according to slope in the order 2°–6° < 25°–90° < 0°–2° < 6°–15° < 15°–25°. Second, the newly developed areas during 2001–2010 had a lower SOC density than the areas built before 1988. Third, urban parks and gardens had a higher SOC density in topsoil, residential green land followed, and scattered street green land ranked last. For hilly cities, the variability of terrain affects the distribution of SOC. The Kriging results indicate that Kriging method combining slope with SOC density produced a high level of accuracy. The Kriging results show that the SOC density to the north of the Jialing River was higher than the south. The vegetated areas were estimated to amount to 73.5 km2 across the study area with an SOC storage of 0.192 Tg and an average density of 2.61 kg/m2.

V-I-S model for cities that are experiencing rapid urbanization and development

This is a study of modeling urban environments from TM satellite images. Urban environments are so heterogeneous that it is necessary to simplify them as combinations of basic land cover materials in order to enable quantitative studies. The V-I-S model proposed by Ridd in 1995 is a conceptual model to simplify urban environments as combination of three basic ground components: vegetation, impervious surface, and soil. Most urban grounds can be interpreted as combinations of these three basic components. This model is used in this study on Shanghai City, China. As a step further, water bodies are masked. From the mixing space, however, we find some difference from the traditional V-I-S model according to the fact that most urban features have their own unique V-I-S composition. The difference can come down to the rapid urbanization and fast development in Shanghai. This is an uncommon course or stage in the development of cities’ urbanization for it may be a case evidence to testify something. Specific urban ecosystem or environment model is built. Percentages of main ground components are extracted from TM data. Various charts and plots are generated to demonstrate the capacity of V-I-S composition on urban land cover analysis. This unique V-I-S composition may provide another ideas for further urban land cover analysis aiming at cities that are experiencing rapid urbanization and development.

Applications of Spatial Interpolation for Climate Variables Based on Geostatistics: A Case Study in Gansu Province, China

Abstract Based on reviewing the origin, development and basic principles of Geostatistics. this article mainly introduces two interpolation methods: Ordinary Kriging and Cokriging. As an optimal one among so many methods to spatial interpolation for climate variables is not available, the article discusses Geostatistics-based interpolation methods by using 30-year average precipitation and evaporation data in Gansu province from 1961 to 1990. According to different semivariogram theory models, we adopt Ordinary Kriging and Bivariate Cokriging interpolation methods, and compare research results. We draw the following conclusions: (1) Both 30-year average precipitation and evaporation present obvious gradient change on space, in a great range. But the formers is larger than the latters. 30-year average precipitation decreases gradually from southeast to northwest, however, evaporation increases gradually from southeast to northwest. (2) According to semivariogram cloud plots and experiment variance minimum principle, we select suitable theoretical semivariogram models based on Geostatistics interpolation, which can simulate the spatially continuous distribution patterns of the special regionalized variables in a better way. Compared with Ordinary Kriging, Cokriging considers the influence of altitude on precipitation and evaporation and thereby has higher interpolation accuracy. (3) Though Geostatistics methods can better reflect the general space patterns of climate variables, their interpolations precision is not high as we expect and can be improved further.

Walkability in urban landscapes: a comparative study of four large cities in China

ContextWalkability is an important element for assessing the sustainability of urban landscapes. There are increased concerns that as the world becomes more urbanized, cities become less walkable.ObjectivesWe aim to develop a composite walkability index to evaluate the spatio-temporal pattern of the walkability of cities. By using the index to evaluate four major cities China, we also aim to provide policy implications.MethodsA comprehensive walkability index is developed to integrate five aspects of the urban built environment: dwelling density, street connectivity, land-use mix, access to public transit, and flatness. Shanghai, Hangzhou, Chongqing, and Lanzhou are chosen as case studies to evaluate the spatio-temporal patterns and changes of walkability in the context of rapid urban expansion.ResultsGreat variations exist among the four cities in terms of speed, scale, and locations of changes of walkability. During 2000–2010, the inner cities of Hangzhou, Chongqing, and Lanzhou and the entire cities of Shanghai and Chongqing increased their walkability index, whereas the inner city of Shanghai had decreased walkability. Furthermore, while inner cities of Shanghai and Hangzhou experienced decreased or stable walkability, the inner cities of Lanzhou and Chongqing enjoyed moderate to high increases in walkability. For inner cities, Shanghai had the highest average walkability index, whereas Lanzhou held the lowest in 2010.ConclusionsThe spatiotemporal changes in walkability seem to be closely associated with governmental policies and planning. The walkability index method can be widely implemented for any urban landscape because of its comprehensiveness, simplicity, and flexibility.

Financing China's Suburbanization: Capital Accumulation through Suburban Land Development in Hangzhou

Chinas rapid urbanization has resulted in substantial suburbanization over recent decades. However, limited research has been conducted into how land-based capital is mobilized, accumulated and circulated within the circuits of the capital accumulation process, or how land-based capital is used to finance massive investment in suburbanization by Chinas local governments, especially since the trend in land commodification during the 2000s. We examined the capital switching experience in the city of Hangzhou and our findings indicate that local governments have attempted to simultaneously strengthen housing development and industrial growth. In contrast to experiences of suburbanization in Western countries, a real estate boom during the early days of suburbanization in Hangzhou was not necessarily the result of diversion of excess capital from over-accumulated investments in the manufacturing industry. Rather, it was a consequence of capital accumulation facilitated by land-reserve systems and land-based financing of infrastructure orchestrated by local government. Local governments and their affiliated land-reserve centers and local investment platforms have acted as entrepreneurs by using profits from suburban property development to subsidize industrial investments and fund the infrastructure-supported expansion of outer suburbs. These findings highlight the potential risks of land-centered accumulation and provide important reflections upon the theory of David Harvey in the context of urban China.

Improvement of linear spectral mixture analysis and experimentation in estimation of urban vegetation fraction

Abundance of vegetation plays an important role in urban ecosystem, urban planning and development. Traditional classification methods on remote sensing data by assigning each pixel membership in one, and only one have the primary shortcomings of their inability to accommodate spectrally mixed pixels in gradational land covers. The traditional classification methods are giving way to spectral mixture analysis (SMA) gradually which is better in acquiring quantitative information for specific land covers. Vegetation fraction, in a general way, is defined as the areal fractions of vegetation within each pixel. This paper, besides introducing the traditional technique of SMA, discusses the improvement of traditional technique from the aspects of data noise removal, least-squares solution with constraining sum of endmembers fractions to unit, pixel purity index and the selection of endmembers. LSMA is tested further with the Shanghai city as an example. Unmixing pixels with root mean square (RMS) error less than 0.02 accounts for the proportion of 98.5%. The spatial distribution of vegetation is corresponding to actual situation. Then we conclude that: the improved LSMA is appropriate for estimating quantitative vegetation fraction and the technique will be widely applied in urban environment. I. INTRODUCTION