Abstract  A box model of the interhemispheric thermohaline circulation (THC) in atmosphere-ocean for global elimate is considered. By using the multi-scales method, the asymptotic solution of a simplified weakly nonlinear model is discussed. Firstly, by introducing first scale, the zeroth order approximate solution of the model is obtained. Secondly, by using the multi-scales, the first order approximate equation of the model is found. Finally, second order approximate equation is formed to eliminate the secular terms, and a uniformly valid asymptotic expansion of solution is decided. The multi-scales solving method is an analytic method which can be used to analyze operation sequentially. And then we can also study the diversified qualitative and quantitative behaviors for corresponding physical quantities. This paper aims at providing a valid method for solving a box model of the nonlinear equation.

Abstract  This paper aims to examine New Economics of Labor Migration (NELM) in the northwestern Guangxi, China and investigate the relationships among rural-urban migration, rural household income and local geographical contexts. Stratified sampling and typical case study were adopted and 236 questionnaires were collected from four villages, Daxin, Lixin, Longhe and Yongchang. We analyzed the rural-urban migration rate, household income and local geographical factors, focusing on the ratio of remittance income to total household income. Data descriptions and statistical methods, such as Pearson Chi-square test, Contingency coefficient, Eta, Pearson correlation coefficient, t-test, multiple comparisons (LSD test, Tamhane T2, Dunnett T3 and Dunnet C test) were used. The results are as follows. Rural households’ income is diversified in survey villages so the motivation of rural-urban migration in the study area can be partly explained by NELM. The migration rate of households (the percentage of households with migrants in survey households) in survey villages varies from 50% to 86%, while the proportion of remittance income to household income is in the range of 30% to 80%. In the village of Yongchang, with the least average arable land area per household, the remittance income plays a vital role in household income (80%). And the statistical findings show that the proportion is significantly and negatively correlated with arable land area per household. The conclusion is that direct effect of migration, i.e., the contribution of remittance to household income, is negatively correlated with the contribution of resources to local income.

Abstract  As the Central Place Theory indicates, the centricity of a central city can influence the extension of its service. Since the service industry in the theory is mostly consumer services, it is worth studying the relationship between the producer services and the centricity of the city in the service society with producer services becoming a more important part of the service industry. The paper takes the case of the Zhujiang (Pearl) River Delta (PRD), a developed region in China, to study the relationship between the developing level of producer services and the urban hierarchy. Based on the analysis about the spatial difference of the producer services in the nine cities of the PRD, and the division of the nine cities according to some economic indices, it is shown that there is a correlation between the developing level of producer services and the urban hierarchy. Furthermore, two deductions about the future status of the producer services in the city and the location of the producer services in a large region can be made from this correlation between the developing level of producer services and the urban hierarchy.

Abstract  The land use patterns in Guyuan City, Ningxia Hui Autonomous Region of China, have changed greatly over the years, due to population growth and farming and stock raising development. This study, using 50-year statistical data of cultivated land and 14-year spatial data of land use pattern, analyzed the developmental stages, the character, and the spatial variance of farmland in the city, and discussed the driving forces of cultivated land changes based on empirical and conceptual statistical models. First, the change of cultivated land area went through different stages of rapid increase, fluctuating change, decrease and rapid decrease from 1949 to 2004, additionally, social and economic policies in different stages had an important impact on farmland variance. Second, from 1986 to 2000, the quantity of cultivated land increased, but its quality decreased. Third, social and economic factors are determinant factors in cultivated land transition. Five constructed paths explain cultivated land transition. Factors that have direct or indirect effects on farmland include the economy (X _eco), the population (X _pop), agricultural output (X _agr), and scientific input (X _sci). The sequence of impact was X _eco>X _pop>X _sci>X _agr. Among all these impacts, X _eco was the major positive one, and X _pop was the major negative one. It is urgent to take measures or adopt a policy to stop the vicious cycle in eco-environment and agriculture production. Otherwise, negative patterns of farmland use will increase, and high-quality cultivated land will continue to decline.

Abstract  The goal of land consolidation in China is still to develop agricultural production. The study of landscape effects of land consolidation projects (LCPs) faces many difficulties because of the lack of government’s interest and data. This paper, taking Tianmen City of Hubei Province in Central China as an example, presents a methodology for analyzing landscape effects of LCPs by GIS and Fragstats3.3. It describes landscape effects with indexes of Patch Density (PD), Largest Patch Index (LPI), Landscape Shape Index (LSI), Interspersion and Juxtaposition Index (IJI), Aggregation Index (AI), and Shannon’s Diversity Index (SHDI), showing more regular shape, simpler structure and less habitat diversity after LCPs. It computes ten landscape indexes of four categories of patches including Cultivated Land, Road, Water Channel, and River and Pond. The indexes show that 1) cultivated land becomes more fragmental in patch area, less irregular in patch shape and more concentrated in block; 2) the transport capacity of roads and irrigation and drainage capacity of water channels have been improved; 3) the landscape change of river and pond can be summarized as decreasing scale, more regular shape, reducing connectivity and diversity of the class. LCPs can facilitate agricultural production as well as protect cultivated land and food security. However, it is doubted that the increase of cultivated land from LCPs results from the reducing in landscape diversity of water area.

Abstract  County-level industrial development and structure upgrade is one of the most important issues of revitalizing old industrial base of China. After the cluster analysis on GDP per capita and GDP per area of each county in Liaoning Province, this paper finds the similarity of population size, land use intensity, and economic development of each county. Location quotient reflects the specialization intensity of industries in each county, and it also reflects the spatial differences of county-level industrial development. Economic development level is higher in the southeast than in the northwest of Liaoning, and the industry driving effect on county-level economy is apparent. The main influencing factors include location, industrial foundation and economic system reform, capital input level, knowledge and technology dissemination, conditions of domestic and overseas markets, population and labor force transfer. Industrialization is an important approach to urbanization for the counties in Liaoning Province. The proportion of agriculture is much higher in the northwest than in the southeast of Liaoning, so it will be take longer time for counties in the northwest of Liaoning to make industrialization, urbanization and modernization.

Abstract  This study investigated the linkages between river water quality and land use in river catchments in Yamaguchi Prefecture, the western Japan, in order to examine the effect of land use changes of both entire catchment and buffer zone on river water quality. Dissolved Oxygen (DO), pH, Biological Oxygen Demand (BOD), Suspended Solids (SS), Escherichia coli, Total Nitrogen (TN) and Total Phosphorus (TP) were considered as river water quality indicators. Satellite images were applied to generating the land use map. Multiple regression model was applied to linking the changes in the river water quality with the land uses in both entire catchment area and buffer zone. The results indicate that the integrative application of land use data from the entire catchment and the buffer zone could give rise to more robust model to predict the concentrations of Suspended Solids (r ²=0.88) and Total Nitrogen (r ²=0.90), rather than models which separately considered land use data in catchment and buffer zone.

Abstract  In this study, remote sensing data of Wuhan City, Hubei Province, China in 1996–2001 were selected to extract wetland landscape information. Several landscape indices were used to evaluate the changes of landscape pattern within the five years, including patch number, patch density, patch fractal dimension, landscape diversity, dominance, evenness, and fragmentation indexes. Then, transformation probabilities of wetland landscapes into non-wetland landscapes were calculated based on Markov Model, and on these grounds the relationship between changes of wetland landscape pattern and urban construction was analyzed. The results showed that fragmentation degree of all wetland types increased, lake area declined, and dominance of natural wetland decreased. The reasons for these results were mainly because of urban construction. According to the features of abundant wetland in Wuhan City, we suggested that protection of wetland landscape should cooperate with urban construction, which means wetland should become important part of urban landscape.

Abstract  Using the daily maximum and minimum temperature dataset from 128 stations from 1960 to 2004 in Northwest China, daily extreme high temperature (EHT) and extreme low temperature (ELT) thresholds were determined by centesimal method for different stations at first, then yearly EHT and ELT events were counted up in different stations, and the characteristics of their spatio-temporal distribution were diagnosed at last. The study drew following conclusions: 1) The consistent anomaly distribution characteristic was the most important mode of the EHT and ELT events in Northwest China. 2) The spatial distribution of the EHT and ELT events can be divided into five sub-regions, namely, the north of Qinghai and west of Gansu, the north of Xinjiang, the south of Xinjiang, the east of Northwest China and the south of Qinghai. 3) The EHT events showed remarkable increasing trend in all of five sub-regions, but only in the north of Qinghai and west of Gansu area, sudden change phenomenon occurred; the ELT events showed decreasing trend in all of five sub-regions, and sudden change phenomenon occurred in Northwest China except for south of Qinghai. 4) In all of five sub-regions the EHT events showed remarkable 12–14yr period oscillation, and the ELT event showed significant 13–15yr and 7–8yr period oscillation. 5) The EHT and ELT events displayed remarkable positive and negative responses to regional warming of Northwest China respectively.

Abstract  Recently, the degradation of permafrost and marsh environments in the Da and Xiao Hinggan Mountains has become a great concern as more human activities and pronounced climate warming were observed during the past 30 years and projected for the near future. The distribution patterns and development mechanisms of the permafrost and marshes have been examined both in theories and in field observations, in order to better understand the symbiosis of permafrost and marshes. The permafrost and marshes in the Da and Xiao Hinggan Mountains display discernible zonations in latitude and elevation. The marsh vegetation canopy, litter and peat soil have good thermal insulation properties for the underlying permafrost, resulting in a thermal offset of 3°C to 4°C and subsequently suppressing soil temperature. In addition, the much higher thermal conductivity of frozen and ice-rich peat in the active layer is conducive to the development or in favor of the protection of permafrost due to the semi-conductor properties of the soils overlying the permafrost. On the other hand, because permafrost is almost impervious, the osmosis of water in marsh soils can be effectively reduced, timely providing water supplies for helophytes growth or germination in spring. In the Da and Xiao Hinggan Mountains, the permafrost degradation has been accelerating due to the marked climate warming, ever increasing human activities, and the resultant eco-environmental changes. Since the permafrost and marsh environments are symbiotic and interdependent, they need to be managed or protected in a well-coordinated and integrated way.