To understand the variations in vegetation and their correlation with climate factors in the upper catchments of the Yellow River, China, Normalized Difference Vegetation Index (NDVI) time series data from 2000 to 2010 were collected based on the MOD13Q1 product. The coefficient of variation, Theil-Sen median trend analysis and the Mann-Kendall test were combined to investigate the volatility characteristic and trend characteristic of the vegetation. Climate data sets were then used to analyze the correlation between variations in vegetation and climate change. In terms of the temporal variations, the vegetation in this study area improved slightly from 2000 to 2010, although the volatility characteristic was larger in 2000-2005 than in 2006-2010. In terms of the spatial variation, vegetation which is relatively stable and has a significantly increasing trend accounts for the largest part of the study area. Its spatial distribution is highly correlated with altitude, which ranges from about 2000 to 3000 m in this area. Highly fluctuating vegetation and vegetation which showed a significantly decreasing trend were mostly distributed around the reservoirs and in the reaches of the river with hydropower developments. Vegetation with a relatively stable and significantly decreasing trend and vegetation with a highly fluctuating and significantly increasing trend are widely dispersed. With respect to the response of vegetation to climate change, about 20-30% of the vegetation has a significant correlation with climatic factors and the correlations in most areas are positive: regions with precipitation as the key influencing factor account for more than 10% of the area; regions with temperature as the key influencing factor account for less than 10% of the area; and regions with precipitation and temperature as the key influencing factors together account for about 5% of the total area. More than 70% of the vegetation has an insignificant correlation with climatic factors.
Global solar radiation (GSR) is the most direct source and form of global energy, and calculation of its quantity is highly complex due to influences of local topography and terrain inter-shielding. Digital elevation model (DEM) data as a representation of the complex terrain and multiplicity condition produces a series of topographic factors (e.g. slope, aspect, etc.). Based on 1 km resolution DEM data, meteorological observations and NOAA-AVHRR remote sensing data, a distributed model for the calculation of GSR over rugged terrain within the Yangtze River Basin has been developed. The overarching model permits calculation of astronomical solar radiation for rugged topography and comprises a distributed direct solar radiation model, a distributed diffuse radiation model and a distributed terrain reflectance radiation model. Using the developed model, a quantitative simulation of the GSR space distribution and visualization has been undertaken, with results subsequently analyzed with respect to locality and terrain. Analyses suggest that GSR magnitude is seasonally affected, while the degree of influence was found to increase in concurrence with increasing altitude. Moreover, GSR magnitude exhibited clear spatial variation with respect to the dominant local aspect; GSR values associated with the sunny southern slopes were significantly greater than those associated with shaded slopes. Error analysis indicates a mean absolute error of 12.983 MJm-2 and a mean relative error of 3.608%, while the results based on a site authentication procedure display an absolute error of 22.621 MJm-2 and a relative error of 4.626%.
The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1:50,000 topographic map data, Landsat TM/ETM+ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963-2007/ 2011 were also analyzed. The results show that: (1) In the period 1956/1963-2007/2011, the Heihe River Basin’s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km2; the total number of the glaciers decreased from 967 to 800. (2) Glaciers in this basin are mainly distributed at elevations of 4300-4400 m, 4400-4500 m and 4500-4600 m; and there are significant regional differences in glaciers distribution and glaciers change. (3) Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate. (4) Analysis of the six meteorological stations’ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to some extent.
Global warming has led to significant vegetation changes in recent years. It is necessary to investigate the effects of climatic variations (temperature and precipitation) on vegetation changes for a better understanding of acclimation to climatic change. In this paper, we focused on the integration and application of multi-methods and spatial analysis techniques in GIS to study the spatio-temporal variation of vegetation dynamics and to explore the vegetation change mechanism. The correlations between EVI and climate factors at different time scales were calculated for each pixel including monthly, seasonal and annual scales respectively in Qinghai Lake Basin from the year of 2001 to 2012. The primary objectives of this study are to reveal when, where and why the vegetation change so as to support better understanding of terrestrial response to global change as well as the useful information and techniques for wise regional ecosystem management practices. The main conclusions are as follows: (1) Overall vegetation EVI in the region increased 6% during recent 12 years. The EVI value in growing seasons (i.e. spring and summer) exhibited very significant improving trend, accounted for 12.8% and 9.3% respectively. The spatial pattern of EVI showed obvious spatial heterogeneity which was consistent with hydrothermal condition. In general, the vegetation coverage improved in most parts of the area since nearly 78% pixel of the whole basin showed increasing trend, while degraded slightly in a small part of the area only. (2) The EVI change was positively correlated with average temperature and precipitation. Generally speaking, in Qinghai Lake Basin, precipitation was the dominant driving factor for vegetation growth; however, at different time scale its weight to vegetation has differences. (3) Based on geo-statistical analysis, the autumn precipitation has a strong correlation with the next spring EVI values in the whole region. This findings explore the autumn precipitation is an important indicator, and then, limits the plant growth of next spring.
The spatially explicit reconstruction of historical land-cover datasets plays an important role in studying the climatic and ecological effects of land-use and land-cover change (LUCC). Using potential natural vegetation (PNV) and satellite-based land use data, we determined the possible maximum distribution extent of forest cover in the absence of human disturbance. Subsequently, topography and climate factors were selected to assess the suitability of land for cultivation. Finally, a historical forest area allocation model was devised on the basis of the suitability of land for cultivation. As a case study, we used the historical forest area allocation model to reconstruct forest cover for 1780 and 1940 in Northeast China with a 10-km resolution. To validate the model, we compared satellite-based forest cover data with our reconstruction for 2000. A one-sample t-test of absolute bias showed that the two-tailed significance was 0.12, larger than the significant level 0.05, suggesting that the model has strong ability to capture the spatial distribution of forests. In addition, we calculated the relative difference of our reconstruction at the county scale for 1780 in Northeast China. The number of counties whose relative difference ranged from -30% to 30% is 99, accounting for 74.44% of all counties. These findings demonstrated that the provincial forest area could be transformed into forest cover maps well using the model.
Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon (SOC) storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011-2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil (0-20 cm) organic carbon storage in grasslands of Inner Mongolia between the 1980s and 2010s. The results showed that: (1) the SOC storage in grasslands of Inner Mongolia between the 1980s and 2010s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m-2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient. (2) SOC changes during 1982-2012 were estimated to be 0.12 Pg C, at 7.00 g C·m-2·yr-1, which didn’t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.
In isotope 137Cs tracing studies, it is a premise to determine suitable 137Cs reference inventory (CRI) plots and the CRI values. Owing to the heterogeneous spatial distribution of 137Cs deposition in the ground and diverse, or even irregular, operations in sampling and testing procedures, CRI determination is usually faced with many difficulties and uncertainties. In addition, more difficulties occur in an investigation of a large-scale region because of time constraints and measurement cost limitations. In this study, traditional CRI acquiring methods were summarized first, and then a new complex scheme was established, involving seven core steps and coupling the model estimate and sample measurement. The above CRI determination methodology was implemented in the central-eastern Inner Mongolia Plateau. The case study results showed that the CRI in the dark chestnut soil sub-region, located in the east and south of Xing'an City, exhibited 2447 Bq·m-2; the CRI in the aeolian sandy soil sub-region, positioned in the south central Tongliao City and central Chifeng City, showed 2430 Bq·m-2; the CRI in the sandy chernozem soil sub-region, situated in the northwestern Chifeng City, presented 2384 Bq·m-2; and the CRI in the chestnut soil sub-region, in the southern Xilin Gol City, was 2368 Bq·m-2. The newly proposed CRI determination scheme was proved effective, and the determined CRI plots and CRI values were convincing. The methodology offered a framework for 137Cs tracing studies in large-scale regions or long-distance transects.
Using the dataset provided by the Smithsonian Institution’s Global Volcanism Program, we have extracted the large volcanic eruptions (volcanic explosivity index ≥ 4) from the period 1750-2010 and have then analyzed the main characteristics of large volcanic eruptions since 1750 according to their geographic latitudes, their elevations, and the years and months in which they occurred. The results show that most large volcanic eruptions were located around the margins of the Pacific Ocean and the islands of Sumatra and Java, especially in the equatorial regions (10°N-10°S). Large volcanic eruptions were concentrated at 1000-2000 m elevations and in the months of January and April. There were more eruptions in the summer half-year (from April to September) than in the winter half-year (from October to the next March). Large volcanic eruptions have interdecadal fluctuations, including cycles of 15-25 years and 35-50 years, which were detected by Morlet wavelet analysis, with the fluctuations being more frequent after 1870 than before. During the periods 1750-1760, 1776-1795, 1811-1830, 1871-1890, 1911-1920 and 1981-1995, there were relatively many large volcanic eruptions.
This study presented a quantitative comparison of cockpit and doline karst by examining the numbers and characteristics of typical types of landform entities that are developed in Guilin (Guangxi, China), La Alianza (PR, USA), Avalton (KY, USA), and Oolitic (IN, USA). Five types of landform entities were defined: isolated hill (IH), clustered hills (CHs), isolated sinkhole (IS), clustered sinkholes (CSs), and clustered hills with sinkholes (CHSs). An algorithm was developed to automatically identify these types of landform entities by examining the contour lines on topographic maps of two cockpit karst areas (Guilin and La Alianza) and two doline karst areas (Oolitic and Avalton). Within each specific study area, the CHSs is the least developed type yet with a larger size and higher relief. The IH and IS entities are smaller in size, lower in relief, and outnumber their clustered counterparts. The total numbers of these types of entities are quite different in cockpit and doline karst areas. Doline karst is characterized by more negative (IS and CSs) than positive (IH and IHs) landforms and vice versa for cockpit karst. For example, the Guilin study area has 1192 positive landform entities in total, which occupy 9.81% of the total study area. It has only 622 negative landform entities occupying only 3.91% of the total study area. By contrast, the doline karst in Oolitic has 130 negative while only 10 positive landform entities. The positive and negative landforms in Oolitic occupy 12.68% and 2.61% of the total study area, respectively. Furthermore, average relief and slope of the landform entities are much higher and steeper in the cockpit karst than the doline karst areas. For instance, the average slope of CHs in Alvaton is 3.90 degrees while it is 19.78 degrees in La Alianza. The average relief of CSs is 4.07 m and 34.29 m in Oolitic and Guilin respectively. Such a difference within a specific area or between the cockpit and doline karst may reveal different controls on the development of karst landscape.
This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth (AOD), the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation (DDV) method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output (MOD09) as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially.
Innovative cities not only constitute an important basis for innovation activities, but also play a strategically critical role in constructing an innovative country, producing new forms of urban development, and fostering urban sustainable development. Currently, China is marching toward the goal of establishing an innovative country by 2020, but in the start-up phase of this process of innovative city construction, the fundamental transition from factor-driven development to innovation-driven development is not being realized. As a result, a wide gap currently exists between China’s innovative cities and the advanced innovative cities in developed countries. This paper argues that this necessary transition is being constrained by a series of bottlenecks in investment, income, techniques, contributions, and talents. The article takes 287 prefecture-level cities as its object of comprehensive assessment, developing a comprehensive assessment system for innovative cities and devising innovative monitoring system software in order to evaluate the current situation in China’s innovative city construction. The analysis addresses four key aspects - namely, independent innovation, industrial innovation, living environmental innovation, and institutional innovation - as well as the spatial heterogeneity of the innovative city construction process. The results demonstrate that the level of innovation in Chinese cities is low, and the paper warns that building an innovation-oriented country will, as a consequence, be difficult. Some 87.8% of the cities studied maintained comprehensive levels of innovation that were lower than the national average. The level of comprehensive innovation in a city was found to have close and positive correlation with economic development. The level of the eastern region of China was, in particular, found to be significantly higher than that of the central and western regions. The levels of urban independent innovation, industrial innovation, environmental innovation, and institutional innovation showed consistent spatial heterogeneity, as did the comprehensive level of innovation in cities. In the future, the authors suggest, China should speed up the construction process in accordance with the basic principles of “independent innovation, breakthroughs in key fields, market-oriented, regional interaction, talent-supported,” with the purpose of building up Beijing, Shenzhen, Shanghai, and Guangzhou as global innovation centers; and Nanjing, Suzhou, Xiamen, Hangzhou, Wuxi, Xi’an, Wuhan, Shenyang, Dalian, Tianjin, Changsha, Qingdao, Chengdu, Changchun, Hefei, and Chongqing as national innovation centers, by 2020. Through this process, China will finally build a national urban innovation network that includes 4 global innovative cities, 16 national innovative cities, 30 regional innovative cities, 55 local innovative cities, and 182 innovation-driven development cities, thereby contributing to the establishment of an innovative country by 2020.
Identifying the problem regions and regional problems, and thus improving regional policies, are crucial for the sustainable development of various economic entities. The coordinated development of industrialization, informatization, urbanization and agricultural modernization (hereinafter referred to as “Sihua”) is not only a practical need but an important strategic direction of integrating urban-rural development and regional development in recent China, and it also provides a significant perspective for identifying problem regions and regional problems so as to improve the regional policies. This study mainly aims to: firstly, establish a comprehensive evaluation index system so as to explore the spatial pattern of coordinated development of Sihua in China at prefecture level; secondly, to develop an evaluation criteria system to identify the problem regions and regional problems from the perspective of coordinated development of Sihua. This paper comes first in the scientific community to evaluate the coordinated development state of Sihua in China at prefecture level and identify the problem regions and regional problems from the perspective of Sihua development by quantitative analysis. This study may benefit the improvement of regional policies and thus contribute to the sustainable socio-economic development of China.
The aim of this paper is to analyze the relationship between mineral resources exploitation and economic and urban development in Xinjiang. The article summarizes the mineral resource exploitation development of Xinjiang especially over the last 50 years, and investigates energy industries and their driving forces, directions, and economic impact on the oasis urban system evolution in Xinjiang. Methods like correlation analysis, location quotient and elastic coefficient are employed in the presentation and discussion, and also field reconnaissance surveys, interviews and secondary sources are used. The result shows Xinjiang’s economic growth is promoted by the contributions of the increasing mineral resource industry which promotes economic development by accelerating infrastructure construction, developing industry and raising revenue and fixed investment. Mineral exploitation in recent years had profound impacts on urban development as a growth engine. The evolution of urban system has a close relationship with resource exploitation, and statistical results provide strong evidence to support the argument that mineral resource exploitation has promoted the growth of built-up areas and its expansion patterns in Xinjiang, especially regions along the northern slope of the Tianshan Mountains.
China’s reform and opening-up policy has brought the country a great development opportunity. The high-speed growth of the economy not only led China to a period of industrialization, urbanization, informatization and agricultural modernization, but also exacerbated the situation of the urban-rural dual structure. Based on the review of current studies, we first used the analytic hierarchy process (AHP) method to evaluate the urban-rural development and transformation level by population transformation index, land transformation index, industrial transformation index and social transformation index between 1996 and 2012 around the Bohai Rim Region. Then, based on the results of each index, we used the exploratory spatial data analysis (ESDA) method to investigate the spatial autocorrelation of the change in the urban-rural development transformation index during the 16-year period using Global Moran’s I index and Local Moran’s I index. Finally, we investigated the mechanism of change of the urban-rural development transformation index at county level, summarizing five main factors: (1) the radiation from the surrounding big cities, (2) the acceleration of the urbanization process, (3) the upgrading of the industrial structure, (4) the publishing and implementation of a macro development strategy and regional policy, and (5) natural factors such as topology.
City growth patterns are attracting more attention in urban geography studies. This paper examines how cities develop and grow in the upper tail of size distribution in a large-scale economy based on a theoretical model under new economic geography framework and the empirical evidence from the US. The results show that cities grow in a sequential pattern. Cities with the best economic conditions are the first to grow fastest until they reach a critical size, then their growth rates slow down and the smaller cities farther down in the urban hierarchy become the fastest-growing ones in sequence. This paper also reveals three related features of urban system. First, the city size distribution evolves from low-level balanced to primate and finally high-level balanced pattern in an inverted U-shaped path. Second, there exist persistent discontinuities, or gaps, between city size classes. Third, city size in the upper tail exhibits conditional convergence characteristics. This paper could not only contribute to enhancing the understanding of urbanization process and city size distribution dynamics, but also be widely used in making effective policies and scientific urban planning.
The traditional data envelopment analysis (DEA), bootstrap-DEA and Malmquist models are employed to measure different tourism efficiencies and their spatial characteristics of 61 cities in six coastal urban agglomerations in eastern China. The following conclusions are drawn. (1) The comprehensive efficiency (CE) of urban tourism using the bootstrap-DEA model is lower than the CE level using the DEA-CRS model, which confirms the significant tendency of the DEA-CRS model to overestimate results. (2) The geometric CE averages of urban tourism in the Yangtze River Delta (YRD) and the Pearl River Delta (PRD) have changed from ineffective to effective since 2000, the averages in the Beijing-Tianjin- Hebei (BTH) and the Shandong Peninsula (SDP) have changed from ineffective to moderately effective since 2000, and those in the Central and Southern Liaoning (CSL) and the West Bank of Taiwan Strait (WBTS) have been ineffective since 2000. (3) The CE values of urban tourism in the PRD, the YRD, the BTH and the SDP have been slightly affected by the pure technical efficiency (PTE), whereas the CE values in the CSL and the WBTS have been slightly affected by the scale efficiency (SE) since 2000. (4) Spatially, the range of geometric averages of the total factor productivity (TFP) for the PRD, the YRD, the BTH, the SDP, the WBTS and the CSL has decreased sequentially, while the one for most cities in six urban agglomerations has exhibited a downward trend since 2000. (5) Collectively, the natural conditions, the economic policies and the tourism capital drive the SE change of urban tourism of the CSL and the WBTS. The tourism enterprises for increasing returns to scale and imitating innovative technology have an effect on the CE change of urban tourism in the BTH and the SDP. The tourism market competition drives the PTE change of urban tourism in the PRD and the YRD. Although the PTE and the SE of urban tourism in six coastal urban agglomerations suffer from uncertain events, the CE maintained overall sound momentum since