Megacities serve as global centers for economic, cultural, and high-tech industries. The structural features and population agglomerations are typical traits of urbanization, yet little is known about the morphological features and expansion patterns of megacities worldwide. Here we examined the spatiotemporal variations of urban land in megalopolises from 2000 to 2020 using the Urban Expansion Intensity Differentiation Index. The fractal features and expansion patterns of megacities were analyzed using the Area-Radius Multidimensional Scaling Model. Urban land use efficiency was then evaluated based on the linear relationship between urban land area and population. We found that Southeast Asia and China were the hotspots of urban expansion in megacities from 2000 to 2020, with urban land areas expanding by 3148.32 km2 and 5996.26 km2, respectively. The morphological features and expansion patterns of megacities exhibited a growing trend towards intensification and compactness, with the average radial dimension increasing from 1.54 to 1.56. The annual decrease in fractal dimensions indicated the integration of inner urban areas. North America and Europe megacities showed a low urban land use efficiency, with a ratio of urban land area to population ranging from 0.89 to 4.11 in 2020. Conversely, South Asia and Africa megacities exhibited a high urban land use efficiency, with the ratios between 0.23 and 0.87. Our results provide information for promoting efficient urban land utilization and sustainable cities. It is proposed to control the scale of urban expansion and to promote balanced development between inner and outer urban areas for achieving resilient and sustainable urban development.
China's mariculture provides more than 60% of the world’s mariculture products and plays an important role in the world’s aquaculture and food supply. Research on changes in the spatial distribution pattern of China’s mariculture, however, remains lacking. To accurately reflect the changes in the spatial pattern of mariculture in China, in this study, we used multitemporal optical and synthetic aperture radar remote sensing images to enhance the characteristics of mariculture and extracted the spatial distribution data for mariculture in China in 2000, 2010, and 2020. Accordingly, we explored the distribution pattern and changes in mariculture in China. We found that, in 2020, China’s mariculture exhibited a distribution pattern of more in the north and less in the south. With the Yangtze River estuary as the boundary, the proportion of mariculture in northern China was 70.9%, and that in southern China was only 29.1%. This difference did not exist in 2000, but it emerged because of the rapid development of mariculture in northern China from 2010 to 2020. In addition, by superimposing the mariculture data with shoreline and water depth data, we found that more than 90% of China’s mariculture area was located in the sea area within 20 km of the shoreline and that more than 80% of the mariculture area was located in the sea area with water depths of less than 20 m. In addition, the spatial distribution of mariculture in China developed from near the shore and moved outward from shallow to deep water areas. We examined the driving factors that influence changes in the spatial distribution of mariculture in China. We argue that technological advancements in mariculture, as well as the intensive concentration of mariculture near the shore, policy constraints and incentives, and economic development, collaborate to shape the current pattern of mariculture development in China.
Polycentric urban development has profound impacts on urban development worldwide. Most studies have identified its complex drivers of social economy and natural condition while ignoring the state-led policy factors. In recent years, China has undergone dramatic administrative division adjustment (ADA) during the process of unique state-led urbanization. However, as a crucial government strategy, the impacts of ADA on urban polycentricity remain unclear. This research investigates the relationship between ADA and urban polycentricity through spatial difference-in-differences models. The results reveal that ADA has contributed to the polycentric urban development in China. Specifically, boundary restructuring has more substantial impacts than hierarchy reorganization. In addition, ADA has significantly promoted urban polycentricity in local cities in central China and neighbouring cities in eastern China, while it has no significant effects in western China. Furthermore, ADA reshapes urban polycentricity mainly by the influencing mechanism of construction land and industrial structure. Policymakers should consider the various ADA’s impacts on urban polycentricity with socio-economic conditions. This research provides a deeper insight into urban spatial transformation with state-led drivers.
Accurately diagnosing and assessing complicated spatial linkages at various scales has become a crucial strategy for enhancing the efficacy of urban government policies and initiatives in the modern era. There is still room for improvement in identifying spatial scale disparities and coupling linkages in cities, although the standard research paradigm on urban sustainability has produced numerous positive outcomes. To advance urban sustainability research from the perspective of spatial coupling, this study used cluster and cross-tabulation analyses for considering urban sustainable development patterns from the requirements of both development scale and spatial accuracy. Subsequently, the spatial unit coupling relationship between district and street scales was explored. Our findings indicated significant scale dependence in the spatial divergence between the built environment sustainability levels of streets and the economic, social, and environmental sustainability levels of districts. The implication is that significant differences exist in the built environment levels of various sustainable development type districts. The scale effect of the spatial coupling relationship influences urban planning and the transition of sustainable development. Maintaining reasonable population density and maximizing the structure and quality of social public resources supply are priorities for streets with the highest habitat sustainability that are located in low-growth type districts. Priority should be given to population deconcentration for high habitat sustainable streets located in synergistic development type districts to increase the level of public service protection. Supporting facilities should be added to medium sustainable streets in low-growth areas to increase the mix of land use, which should encourage additional production activity concentration, thereby fostering overall economic strength. Further, increasing the accessibility of local public service facilities for low and medium sustainable streets located in ecologically biased areas should be prioritized, but a green and low-carbon orientation should be maintained during building.
The construction of rural life circle has an essential impact on the change of rural social space. Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space. Using social behavior as a link, we construct a logical relationship framework between rural life circle and social space. Based on the survey data of Baijia village in the loess hilly region, this paper analyzes the characteristics and adaptability of the two and discusses preliminary ideas of life circle reorganization and social space reconstruction. The study results are as follows: (1) Based on the location of four types of service facilities and the travel mode of villagers, two life circles of 15 min and 25 min have been formed in Baijia village. The rural social spaces such as communicative behavior space, health seeking behavior space, leisure behavior space, and consumption behavior space show a specific concentric circle structure and unique hierarchical structure. (2) The analysis of the adaptation between them shows that the 15 min life circle in Baijia village has a high level of adaptation to communicative and leisure behavior spaces. It plays a positive feedback role in the construction of social space. However, it has a low level of adaptability to the space of health seeking and consumption behavior spaces and has a negative feedback effect on the construction of social space. The 25 min life circle is the opposite. (3) The reorganization of facility layout, hierarchical structure, and service functions in the village life circle will lead to changes in the range, frequency, and purpose of villagers’ behavioral activities, resulting in a new social spatial pattern. These findings are important for formulating village development and construction plans, improving the settlement habitat, and reconstructing the order of social life.
Land use transition occurs through changes in land use morphologies. The decision-making and land use behavior of farmers is the main factor that causes changes in the land use system and subsequent transitions of land use. This study focused on the recessive morphologies of farmland based on the investment in agricultural production inputs by farmers, and established an analytical framework based on induced technological innovation theory and farmers’ behavior theory, which followed the pathway of “objective-willingness- behavior.” Using survey data for farming households in two counties (Shouguang and Yiyuan) in Shandong province, the main factors influencing farmers’ willingness to invest in agricultural production and their differences under the background of labor force changes were comprehensively analyzed with a binary logistic model and ordinary least squares (OLS) regression model. The aim was to provide decision-making guidance for promoting farmland use transition. There were three key results. (1) The scale management objectives of a farmer were limited, with 75% of farmers intending to maintain the current farmland management scale, and planning to retire at an advanced age, although there were regional differences in these phenomena. (2) Farmers’ willingness to invest in agricultural production inputs was closely related to agricultural production objectives, farmland use, and agricultural production, whereas the labor structure had no significant effect. Farmers’ behavior toward investment in agricultural production inputs was negatively related to their expected retirement age. Changes in the household labor structure were an important factor boosting farmers’ investment in agricultural production inputs. (3) It is essential to better understand the cognitive level and structure of farmers, and the characteristics of the labor structure and type of agricultural development could be combined to improve the farmers’ cognitive level and willingness to adopt scale management objectives and generate behavioral responses. Using the dual scale of “land + service” would overcome the structural obstacles faced by farmers, and effectively play the role of providing both policy incentives and regulation.
The integration of culture and tourism is conductive to the realization of urban-rural integration and rural revitalization. Taking 16 typical traditional villages in Beijing as cases, this study proposes an evaluation system and influencing factor model for the integration of culture and tourism in traditional villages. Based on the TOPSIS model supported by the entropy method, the level of culture and tourism integration in traditional villages is analyzed. Moreover, we discuss the main factors influencing the integration of culture and tourism in traditional villages and their paths by using fuzzy-set qualitative comparative analysis (fs/ QCA). The results can be summarized in four main areas. (1) The integration of culture and tourism in traditional villages is a dynamic process that continues to promote the comprehensive revitalization by deepening resource integration, advancing product cultivation and strengthening industry functions. (2) There are obvious differences in the development levels of the integration of culture and tourism among the case villages. Specifically, the levels of each village in the four dimensions present the characteristics of differentiation and imbalance. (3) No single factor can capture the necessary and sufficient conditions for the integrated development of culture and tourism. (4) There are three paths influencing the integration of culture and tourism in traditional villages, namely, the mature development path, the rapid development path and the progressive development path, which correspond to their respective combinations of influencing factors. The results of this study can provide theoretical inspiration and scientific guidance for the urban-rural integration and rural revitalization of traditional villages from the perspective of the integration of culture and tourism.
In the past 30 years, observational climate datasets reveal a significant a drying and warming trend over in North China. Understanding of climatic variability over North China and its driving mechanism in a long-term perspective is, however, limited to a few sites only, especially the lack of temperature reconstructions based on latewood density and blue intensity. In this study, we developed a 281-year latewood blue intensity chronology based on 45 cores of Picea meyeri in western North China. Based on the discovery that the warm season (May-August) mean maximum temperature is the main controlling factor affecting the change in blue light reflection intensity, we established a regression model that explained 37% of the variance during the calibration period (1950-2020), allowing to trace the mean maximum temperature up to 1760 CE. From the past 261 years, we identified seven persistent high temperature periods (1760-1773, 1778-1796, 1805-1814, 1869-1880, 1889-1934, 1984- 2000, 2004-2020) and three persistent low temperature periods (1815-1868, 1935-1963, 1969-1983) in North China. Comparisons of a nearby temperature reconstructions and climate gridded data indicate that our reconstruction record a wide range of temperature variations in North China. The analysis of links between large-scale climatic variation and the temperature reconstruction showed that there is a relationship between extremes in the warm season temperature and anomalous SSTs in the equatorial eastern Pacific, and implied that the extremes in the warm season temperature in North China will be intensified under future global warming.
Rainfall temporal patterns significantly affect variability of flash flood behaviors, and further act on hydrological model performances in operational flash flood forecasting and warning. In this study, multivariate statistical analysis and hydrological simulations (XAJ and CNFF models) were combined to identify typical rainfall temporal patterns and evaluate model simulation capability for water balances, hydrographs, and flash flood behaviors under various rainfall patterns. Results showed that all the rainfall events were clustered into three types (Type 1, Type 2, and Type 3) in Anhe catchment in southeastern China. Type 1 was characterized by small total amount, high intensity, short duration, early peak moment, and concentrated hourly distribution. Type 3 was characterized by great total amount, low intensity, long duration, late peak moment, and uniform hourly distribution. Characteristics of Type 2 laid between those of Type 1 and Type 3. XAJ and CNFF better simulated water balances and hydrographs for Type 3, as well as all flash flood behavior indices and flood dynamics indices. Flood peak indices were competitively simulated for all the types by XAJ and except Type 1 by CNFF. The study is of significance for understanding relationships between rainfall and flash flood behaviors and accurately evaluating flash flood simulations.
Road network expansion can result in the fragmentation of ecological landscapes due to the transformation of landscape processes and patterns. However, knowledge about these processes and patterns is scarce. In this study, the road network and landscape patterns in the Dongzhi tableland of the Chinese Loess Plateau (CLP) between 2005 and 2020 were characterized, and their spatial relationships were analyzed. The results showed that (1) the kernel density estimation (KDE) method is useful in characterizing road network density. When the bandwidth value is four, the boundary of the road network kernel can be distinguished clearly. (2) The road network in the tableland expanded greatly over the past 15 years, and the total area of road kernels in the Dongzhi tableland increased from 55.73 km2 in 2005 to 223.55 km2 in 2020. (3) High-density road networks were generally distributed on cultivated and constructed lands where the slopes were generally 0°-5°, while low- and medium-density road networks were mostly distributed in grassland areas where the slopes were greater than 5°. (4) Road network density is closely related to the coverage of cultivated and constructed lands. The results of this study are helpful in understanding the potential impact of road network evolution on the landscape at a regional scale.
