China has been highlighting the planning and construction of the Yangtze River Economic Belt (YREB), radically every ten years. This indicates the important strategic roles of the YREB in China, which has resulted in great academic achievements in studying the YREB. These achievements raise an academic question: what is the new perspective on studying the YREB in the new era? This paper will systematically review the macro development trend at national and international levels and the general characteristics, issues and trends of the YREB. Based on the previously developed innovative theories and methods in the areas of regional development and the relevant studies on the YREB, this paper aims to propose three new perspectives on its future development. The first perspective of river basin is focused on coupling all the elements of the YREB. The second perspective of dual-nuclei concentrates on the spatial layout of the YREB. The third perspective of livability will look at the human settlement environment of the YREB. Specifically, the development of this region should be dependent on the economic strength of the river basin, using the three-level basin as a basic unit. Its socio-economy and resource and environment elements should be systematically integrated and coupled and spatially matched. Such analyses are used to refine the spatial development types and patterns, and particularly to achieve the coordination between socio-economic and resource and environment systems. Meanwhile, the macro strategic roles of the YREB in China should be explicitly positioned within the background of 'One Belt One Road' national strategy. The internal relationships between the YREB and other central cities should be clearly analyzed through its external pathways and doors. The patterns of infrastructure and evolution of cities and towns within the YREB should be clarified using the theory of dual-nuclei structure. Furthermore, the evolution process and essential mechanisms of the three urban agglomerations can be analyzed in details. These analyses facilitate the classification of human settlement types and the assessment of environmental livability from the perspective of environmental livability, which will provide policy suggestions for the pilot and demonstrative zones of environmental livability at the national level.
Improving the urbanization rate of registered population is regarded as a new target of building a moderately prosperous society in China. The gap between urbanization rates of residential population and registered population is caused by the large floating population. The research on urbanization rate of registered population is helpful for understanding the new urbanization process in China. This paper clarified the statistic definitions of "local", "nonlocal" and "urban" for urbanization rate of registered population. Then two calculation methods, which were direct method and indirect method, were put forward to measure urbanization rate of registered population. Based on the 6th census data in China, the urbanization rate of registered population at county scale in 2010 was calculated. Besides, the comparison was conducted between urbanization rates of registered population, residential population and floating population. The main conclusions are as follows. (1) Urbanization rate of registered population was obviously lower than that of residential population. In 2010, the urbanization rate of residential population reached 50.27%, while that of registered population was only 39.34%. The cities and counties with a large immigrant floating population usually have a relatively high urbanization rate of residential population. (2) The urbanization rate of registered population had a significant positive correlation with non-agricultural opportunities. Thus the urbanization rates of registered population in the coastal area, areas along the Yangtze River and in northern border area were relative higher than that in the inland area. The immigrant floating population mostly gathered in urban agglomeration area and provincial capital cities. As a result, in these areas and cities, urbanization rates of residential population were usually higher than that of registered population. (3) In China, two thirds of cities and counties had a relatively low urbanization level. The urbanization rates of all the three types in these cities and counties were below the national average level. The central and western regions of China should raise urbanization rate of registered population through encouraging local urbanization development. While those well-developed urban agglomerations and provincial capital cities should upgrade urbanization rate of registered population through promoting citizenization of immigrant floating population.
Nowadays family migration has become the main migration pattern of floating population in China, which may raise new requirements for residential independence, tenure and quality in the cities. For some researchers, the migrant households were generally considered as passive recipients of housing inequality, and the institutional barrier of Hukou were no doubt still the decisive factors for migrants' housing outcomes. However, other researchers start to challenge this perspective, and argue that migrants should be considered as enabling agents with coping strategies in the housing market since the influence of Hukou system in migrants' housing outcomes is declining. Under this context, this paper tries to explore the role of family strategy in family migrants' housing outcomes, and whether this conclusion differentiates among various households. Based on a questionnaire survey which covered 2394 migrants and their households in 12 cities of the Bohai Rim Region, the Yangtze River Delta Region, the Pearl River Delta Region, and the Chengdu-Chongqing Region, this paper uses logistic regression model to explore family migrants' urban housing outcome in terms of housing tenure and quality and the mechanism for this. The result shows, different household arrangements lead to diversification of housing outcome, which means that the ownership and housing quality differs significantly among sole migrants, couple migrants, two-generation migrants, and three-generation migrants. The three-generation migrant households, as expected, have the highest ownership percentage and residential quality among all types of migrant households, while the sole and couple migrants suffer from the poor residential conditions. This housing outcome should be explained by factors such as socio-economic characteristics, household arrangements, geographic environment, migrants' connection with the original hometown and adaptation to current destination. Especially, when considering the effect of migrants' sense of belonging, plan to settle down in the destination and connection with hometown, the effect of Hukou is weakened. Different household arrangements have different barriers and strategies, which leads to the divergence of housing outcomes. The implication from this research is that the governments should make gradient regulation policy for the diverse family migrants, and lead them to settle stably step by step.
With the rapid development of ICTs and big data technology, various "flow" data have become easier to be obtained such as population flows, information flows and capital flows. These data are key material to build the production network, social network, urban network and other types of network, which are becoming very important research subjects of geographical sciences and enrich the research content of this field. So far, researches on the networks in geography are still in their infancy stage. There are a number of methods that have not been utilized effectively, while it is difficult to find a proper abstracted network model to simulate the geographical phenomenon in many occasions. Therefore, to seek more appropriate methods and models for geographical network studies undoubtedly become urgent tasks in this field. In this context, an exploratory research was carried out. First, population flow network of China in the period of "Chunyun", a typical directed-weighted urban network, was built based on the population flow data acquired from “Big data on human migration during the "Chunyun" period from Baidu Map ("Baidu migration data" in short). Sequentially directed alternative centrality and directed alternative power were proposed in predecessor's foundation to evaluate the importance of each node and divide these nodes into different types according to their roles in the urban network. As analysis result, two dimensional spatial characteristic and geographical spatial characteristic was revealed which endowed the methods more practical significances. To validate the effectiveness of the methods, a contrastive analysis of the directed alternative centrality/directed alternative power and centrality/directed alternative power in previous studies was conducted. Based on directed weighted urban network and with the help of this method, this paper classified the cities into quintessential cities, hub cities, gateway cities and periphery cites, and identified the characteristics of agglomeration and diffusion at the mean time. And the result of classification was explained according to the internal structure and external context of the population flow network during the "Chunyun" period. It is found that the regional difference of directed alternative centrality and directed alternative power have certain relationship to economic and social development, national development strategy and administrative division. This explorative process demonstrated that one can effectively extract the information on the hierarchical structure, function divergence and imbalance of the directed weighted urban network via the directed alternative centrality-directed alternative power method. Directed alternative centrality-directed alternative power method is really a feasible approach to analyze the geographical network, and it also demonstrated that directed-weighted urban network can really make a difference from undirected and unweighted network in the geographical network studies.
This paper adopted the method of the ratio of construction land equivalent area to the total area to calculate human activity intensity at county level in the Loess Plateau region. On the basis, the overall change of human activity intensity, its spatial-temporal differentiation, geographical unit change and spatial autocorrelation were analyzed. The results were shown as follows. (1) Human activity intensity was 12.48% in 1992 and 14.49% in 2000. But it only rose to 14.81% in 2008. Before 2000, it grew fast. After that, the growth decelerated markedly. (2) Characteristics of spatial pattern of human activity intensity were that the northwest was low and the southeast was high. Human activity intensity in the central parts changed from lower type to lower-medium type. The type of very high and high was relatively stable. However, the range of the medium type greatly expanded. The scope of the type of low and very low narrowed down obviously. (3) The type of low and very low changed into the medium one in many parts of the loess hilly region. The spatial pattern of human activity intensity changed little in the other five natural geographical units. Valley-basin area and Hetao Plain were characterized by the levels of very high, high and medium. Multiple types were distributed in the eastern mountainous area. The loess hilly region was featured by the levels of medium and low. Erdos windy-sandy area had a characteristic of the types of low and very low. (4) Human activity intensity had obvious spatial agglomeration. Before 2000, spatial agglomeration level was increasingly strengthened. After that, it was relatively stable. High-value concentrated areas were mainly distributed in the Fenhe-Weihe Valley and northwestern Henan. Low-value concentrated areas was found in the Erdos windy-sandy area, the loess hilly region and eastern Qinghai Plateau. (5) Human activity intensity and population density were correlated under the significance level of 0.01. The correlation indicated that population density played an important role in the change of human activity intensity. Besides population density, human activity intensity was also influenced by natural and socio-economic factors, such as terrain, water resource, energy and mineral resources and traffic condition. There were good natural conditions and high socio-economic development level in the Fenhe-Weihe Valley, Taiyuan Basin as well as northwestern Henan, with the human activity intensity being higher that other regions. It was just opposite in eastern Qinghai Plateau and Erdos windy-sandy area etc. Because of the rich energy and mineral resources, human activity intensity was high or medium in some parts of Shanxi province.
Rural-urban fringe is an important part of urban and regional spatial structure in China. Zone location of rural-urban fringe, together with multi-functionality of agriculture, gives agriculture in rural-urban fringe distinct and diversified regional functions. Both production function and service function of agriculture in rural-urban fringe has made great contribution to urban and rural development, which is also helpful to overcome difficulties growing out of urbanization. This paper constructs an index system to calculate the execution of regional function of agriculture in rural-urban fringe. The result of Beijing case shows that in the last 10 years, the calculations fluctuate markedly, with an iterative process of decline-rally-decline. Specifically, indexes such as agricultural labor productivity and farmer income, which were obviously affected by macro-economic growth. At the same time, ecological construction has achieved great results. However, the functions of production and supply of agricultural production, the satisfaction of the consumer demand of leisure and recreation, and the contribution of expanding employment are relatively week. Moreover, the combination of agriculture in rural-urban fringe and modern urban industries does not consistent with the realistic demand.In the developing process of rural-urban fringe, economic benefits have usually been overemphasized and others neglected. Moreover, the deficiency of scientific planning, and the weakness of operation innovation of agriculture exacerbates the reduction of regional function of agriculture in rural-urban fringe. In Western countries, world cities have extensive agricultural spaces to promote ecological management and sustainable development, although industrial increase and urban sprawl needs a large amount of lands. In China, however, complete urbanization is still the coincident selection of most of cities in the process of rebuilding rural-urban fringe. Under the background of new-type urbanization, regional function of agriculture in rural-urban fringe should be enhanced.
In recent years, rural hollowing has become a common phenomenon in China's rural social and economic development .The essence of rural hollowing is considered to be an important part of the evolution of rural regional systems in the urban-rural transition. China is currently in a critical period of urban-rural transition and reconstruction. Urban and rural population mobility, as well as the reorganization and interactions of socio-economic development factors, have accelerated. A direct result is rural overpopulation, idle homestead, and economic backward. In some areas, there has emerged an obvious "rural disease." Therefore, understanding the regional differentiation of the rural hollowing during the new period, adapting to the new trends of rural population mobility and changes in villages during the process of new urbanization, and optimizing the rural population, industry, and use of land space are important strategic issues to be solved urgently, and are important problems in rural geography that need to be solved. By constructing the frame and index system, which measures the three aspects of land, population and economy of rural hollowing, 23 counties and districts of Changsha, Zhuzhou and Xiangtan area were used as the research units. Using the entropy method, multi-index comprehensive evaluation and multiple regression analysis, the spatial variability of rural hollowing was investigated, and the key influencing factors and mechanisms of hollowing were also discussed. The results show that the hollowing of land in Changsha, Zhuahou and Xiangtan agglomeration is gradually reduced from the center of the city to the fringe. The hollowing of the population is characterized by a high area in the central part, whilst there is low area in the northern part. The high and low distributions of economic hollowing have very similar characteristics to the low and high distributions of population hollowing. The spatial distribution of the comprehensive hollowing is unbalanced, and dominated by middle and low levels, with the spatial distribution of gradually slowing down from the central city to the east and west of the urban fringe. The distance from the central city has a more obvious influence on the spatial distribution of the comprehensive hollowing level. There are great differences in the modes, degrees and intensities of various factors. The increase in the income of farmers and the development of the regional economy, the size of the rural population, and the change in the employment structure are the leading and direct influencing factors of rural hollowness, land use patterns and efficiency changes, which inhibit the aggravation of the degree of rural hollowing.
With the growing importance of University-Industry cooperative innovation (U-I cooperative innovation) in regional innovation, there is an increasing concern over the factors influencing U-I cooperative innovation. While U-I cooperative innovation features a process of knowledge transfer, multi-dimensional proximity is an appropriate analytical perspective to study the influencing factors of U-I cooperative innovation. This paper argues that geographical proximity, cognitive proximity and social proximity are essential elements of a conceptual framework for the analysis of U-I cooperative innovation, which contains heterogeneous organization. As such multi-dimensional proximities represent an important factor in the promotion of U-I cooperative innovation, interactive learning has been proved to be the way to realize knowledge transfer under the influence of multi-dimensional proximities for cooperative subjects—since frequent and continuous interaction between U-I cooperative subjects can enhance the level of U-I cooperation. By constructing a theoretical framework of "Multi-dimensional proximities, geographical proximity and related proximities→Interactive learning→Level of cooperation", and based on a multi-case study methodology, this research takes high-tech enterprises in the Guangzhou Development District as an example and explores the influence of multi-dimensional proximities on "point to point" U-I cooperative innovation. The research findings show that: (1) while geographical proximity, cognitive proximity and social proximity all contribute to the level of U-I cooperation, these positive effects vary at different stages of technological innovation; (2) whilst interactive learning has significant moderating effects on multi-dimensional proximities and the level of U-I cooperation, there are noticeable periodic characteristics in its effects in terms of content, way and intensity; (3) geographical proximity, cognitive proximity and social proximity, respectively, have complementary and substitutive effects on the level of U-I cooperative innovation, although the effects may vary in different stages. In the interaction between different types of proximities, the positive influence of complementary effects is usually greater than that of substitutive effects. The conclusion is useful for us to understand the interaction process between the innovation subjects under different circumstances of proximities; in addition, it can also provide evidence for policy-making as regards rational distribution of scientific and technological resources, selection of U-I cooperative partners, as well as appropriate responses to different circumstances of proximities in the process of technological innovation cooperation.
Industrial transformation is a hot topic for resource-based cities. Based on the input-output table of Tangshan in 2002 and 2012, the whole structural increase of industries in Tangshan and their impact factors are analyzed by the increasing causative matrix and probit model. The results show that, there was not a structural increase in the sector of coal mining and processing and the sector of metal smelting and pressing from 2002 to 2012. Tangshan has been out of the development mode with the high dependency on coal and steel. Some sectors have experienced a structural increase characterized by the high technology, such as special equipment, instrumentation and cultural office machinery manufacturing, as well as information transmission software and information technology services. All of the indications illustrate that Tangshan has shown a trend of industrial transformation. As for the impact factors of industrial structural increase, it is found that the industrial influence coefficient has a negative effect, while the industrial sensitivity coefficient, GDP proportion of industrial value added, and industrial direct value added ratio have positive effects. Finally, it is helpful to improve the ratio of direct value added and linkages with downstream industries for the industrial transformation of the resource-based cities.
The Malacca Strait, the Suez Canal and the Panama Canal are the main channels in the global container shipping network. As the dependence of the world economy on container shipping constantly increases and terrorism wantonly spread, research of the impact of main channel interruption on the global container shipping network and China container shipping is of great significance in analyzing the vulnerability of the global container shipping network, establishing and improving the security mechanism of the global economy operation and guaranteeing unobstructed container shipping between China and other regions. To study the impact, we performed a statistical analysis of all ports and shipping lines that are operated by the top 100 container shipping companies in 2015, which occupy 93% of the global container shipping capacity. The results indicate that there are 2827 shipping lines and 734 ports in the global container shipping network. Based on the statistics, we calculated the change rates of network average degree, isolated-node proportion, clustering coefficient, network average shortest-path length and network efficiency of the network when the main channels are attacked respectively. The average of the change rates of the network's metrics are 5.61%, 3.50% and 1.89% when the Malacca Strait, the Suez Canal and the Panama Canal are attacked respectively. So the network is sensitive to the three main channels, and the Malacca Strait is the most influential channel, followed by the Suez Canal and the Panama Canal. At the same time, we analyzed the impact on China container shipping by combining the characteristics of global marine geography. The node degrees of 12, 6 and 6 ports in China decrease when the main channels are attacked respectively, and the network shortest-path lengths between the affected ports in China and other ports in the world increase in varying degrees, so the transport efficiency decreases obviously. Finally, to guarantee unobstructed container shipping between China and other regions, we present the alternative shipping lines by detour transportation or sea-land multimodal transportation according to different main channels, and make corresponding policies from the maritime security perspective.
Cultivated land is the foundation for sustainable development in China. The growth in both population and trade in China has triggered the increasing demand for food in recent years. However, aggressive urbanization continues to appropriate cultivated land. As a result, the conflict between food supply and demand has become prominent, and academics have become increasingly concerned with several challenges regarding cropland pressure. Existing research shows that it is particularly necessary to examine cropland pressure patterns in China at a smaller scale and analyze impact factors from more perspectives. Therefore, this article uses the pressure index of cultivated land to evaluate cropland pressure levels with 342 prefectural-level units. On this basis, we have analyzed the spatial-temporal differentiation and evolution of China's cropland pressure pattern from 2001 to 2013 using the GDI index, spatial autocorrelation, and the average growth index. Finally, based on the dual perspectives of grain production and social economy, we have established the impact factor evaluation system of 'quality of cultivated land + agent of agricultural production input + economic environment + farmers' income' and explored the main impact factors that cause change in China's food security, particularly socioeconomic factors. We found the following results. First, China's cropland pressure has been decreasing since 2001, but greater changes have taken place in the degree of spatial differentiation and the trend of accumulative spatial agglomeration. Specifically, the spatial agglomeration of high cropland pressure areas have become increasingly obvious. Second, China's cropland pressure pattern is generally stable with minor changes, and there is an obvious north-south differentiation trend; cropland pressure in areas along the southwest and southeast coasts increases quickly. Third, socio-economic factors, including farmers' income, economic level, and industrial structure, have a more obvious impact on changes in cropland pressure. The effect of these factors exceeds that of the grain production input factor. Furthermore, the quality of cultivated land is the fundamental factor that determines cropland pressure.
The snow cover over the Tibetan Plateau (TP), as a sensitive indicator of climate change, has a significant impact on regional and even global climate. MODIS 8-day snow cover extent products and ERA-Interim reanalysis data were employed to study the spatial and temporal variability of the snow cover over the TP and its relation to Arctic Oscillation (AO) by climatological statistical diagnosis. The spatial distribution of winter snow cover over the TP is far from uniformity, with high snow cover fractions (SCF) at the western edge and the southeast part of the TP but scarce snow in the northern and central parts. It is found that the SCF is out of phase between the eastern and western parts of the TP with respect to the leading mode of empirical orthogonal functions (EOF1), namely, the positive (negative) anomalies in SCF over the eastern part of the TP are associated with negative (positive) anomalies in SCF over the western part. This pattern is positively correlated with AO. During the positive AO phase, the East Asian Trough weakens, together with intensive Southern Branch Trough. The warm moist flows easily lift to the eastern part of the TP because of intensive Subtropical High over the Western Pacific and result in excessive snowfall, while an anomalous anticyclone with its center to the southwest of the plateau leads to sinking dry air flows over the western TP, which is not prone to snowfall, and the corresponding higher surface temperature is also against maintaining the snow cover. During the negative AO phase, the East Asian Trough strengthens and so does the East Asian winter monsoon, with dry cold air flows over the eastern part of the TP, leading to less snowfall. On the other hand, an anomalous cyclone centered to the southwest of the plateau makes it easier for the warm moist flows from the Bay of Bengal and Arabian Sea to lift to the western part of the TP and meet the cold air from Siberia, thus prompting more snowfall over the western part of the TP.
Studying the characteristics of extreme high temperature events under the changing environment is important for the mitigation and adaptation of climate change, as it provides theoretical basis for local disaster prevention and mitigation. How to quantify the non-stationary extreme high temperature and its changes has not well established so far. In this paper, two extreme high temperature indices, i.e. annual mean maximum temperature (AMMaxT) and high temperature intensity (HI), are proposed to describe the extreme high temperature events in the Heihe River Basin. Daily temperature observations from 1960 to 2010 of nine meteorological stations in the Heihe River Basin are collected. Four different statistical tests methods (including Mann-Kendall test, Spearman rank correlation test, Rank sum test and Pettitt test) are employed to detect the non-stationary characteristics of the two extreme high temperature indices. Eight theoretical probability distribution models (including Bate, Gamma, GEV, GPD, Log-Logistic, Lognormal, Wakeby and Weibull) are used to fit the frequency characteristics of the two indices. Trend analysis and change point detection show that nearly all the nine stations have experienced significant trends and obvious change points in both AMMaxT and HI series, and the main variation type is change point variation. Since the theoretical probability distribution models are commonly used to fit the stationary series, the non-stationary AMMaxT and HI series in this study are modified to be stationary by means of the backward restore for consistency. All of the eight probability distribution models can give good fittings to the modified AMMaxT series, while only three of the eight models, i.e. the GEV, GPD and Wakeby models give satisfactory fittings to the modified HI series. According to the ranking of goodness of fit, the GEV and Wakeby models perform the best for both AMMaxT and HI series. Considering its wide applications in other related researches, the GEV model is finally selected as the optimum theoretical one for fitting the extreme high temperature indices in the study area. Based on the GEV model, we calculate the estimated return levels for both the modified and non-modified extreme series at different return periods, and assess the changes of the extreme series at three different return periods (i.e. 10-year, 20-year and 50-year). Overall, the estimated return levels for non-modified extreme series are greater than those for the modified series. This means that the extreme high temperature indices in the study area present trends of increased intensity, shortened return period and increased frequency, which is consistent with the changes of temperature in Northwest China.
Western Henan Mountains, the extent of Qinling Mountains in Henan province and the transition from subtropical to warm temperate zone, are sensitive to climate change. This study sought to analyze vegetation NDVI change and its response to climate change in this sensitive area in multi-dimensions because the multi-dimensional ecological unit analysis is conducive to vegetation protection and ecology restoration in mountain ecosystems. We firstly used S-G filtering algorithm to reconstruct the MODIS-NDVI time-series data from 2000 to 2013 and combined DEM, temperature and precipitation data in the study area; then we used statistical analyses (i.e., linear regression, correlation analysis, and so on) to study vegetation NDVI change and its response to climate variables (temperature and precipitation) in different terrain factors (elevation, slope, and aspect). The results showed that: (1) in 2000-2013, there was a significant growth of vegetation NDVI in the study area, and the growth rate was 0.041/10a. The finding suggested that, in general, the vegetation in the Western Henan Mountains was positively developed in this area. Meanwhile, the mean NDVI value increased with the increase of elevation, and then the trend became decreased; while it gradually increased as the slope increased. The mean NDVI value, however, had no significant differences in each aspect. (2) The recovery probability of vegetation in <1100 m regions was the highest, whereas the degradation probability in >1700 m regions was the highest. Regarding the slope, the recovery probability of vegetation in 10°~20° regions was the highest, while the degradation probability in 0°~5° regions was the highest. The variation of recovery (or degradation) probability of the aspect was not obvious somehow. (3) Vegetation in different terrains was affected by distinctive climate factors. Specifically, vegetation NDVI change at high elevations had stronger correlation with precipitation than with temperature, which indicated that the vegetation dynamics in this range was mainly affected by precipitation change. Inversely, vegetation NDVI change on different slopes had closer relationship with temperature than with precipitation. Not surprisingly, in different aspects there was little difference in terms of the response of vegetation NDVI to climate variables. (4) NDVI growth rates on the north slopes of sub-mountains, such as Xiaoshan, Xionger, and Funiu, were much higher than those on the south slopes. Moreover, the vegetation on the north slopes was more sensitive to precipitation change, whereas on the south slopes it was more sensitive to temperature change. All this echoes the importance of studying the response of local ecological environment to mountain ecosystems in transition zone under the background of global climate change.
Over the last several decades, many studies proved that the first flowering date (FFD) of most plant species has become earlier in response to global warming. However, the existing results about the impact of climate change on the flowering duration (FD) were quite limited. In this study, we investigated the temporal distribution and trends in FFD, end of flowering date (EFD) and FD of 40 plants from 1978 to 2014 in Mudanjiang, China. Correlation and regression analyses were used to examine the relationship between the flowering phenophases and the preseason temperature. Meanwhile, we have evaluated the applicability of two phenological models (including the regression model and the growing degree day model) in simulating the flowering phenophases. The results showed that: (1) During the observation period, the mean FFD and EFD of the 40 plant species ranged from April 13 to August 27 and from April 25 to September 13, respectively. However, most of FFD and EFD were concentrated in May. The FD ranged from 6 to 69 days, with most of them (62.5%) ranging between 10 and 20 days. (2) During the study period, FFD became later at a mean rate of 0.06 days decade-1 with only one species showing a significant trend (P<0.05), while EFD occurred earlier at a mean rate of 0.28 days decade-1 (no one significantly). The averaged FD has shortened by 0.35 days decade-1 with only four species showing a significant shortening trend (P<0.05). (3) Most species showed a significant correlation between FFD (or EFD) and preseason temperature. The temperature sensitivities of FFD ranged from -6.2 to -2.3 days/°C-1, while those of EFD varied from -5.0 to -1.2 days/°C-1. The unapparent trends of flowering phenophases were probably due to the unobvious variation of spring temperature in the study area. (4) The regression model has successfully simulated the interannual changes in FFD and EFD with the mean goodness of fit (R2) ranging from 0.38 to 0.65, but failed to simulate FD accurately (mean R2 was 0.17). Compared to the regression model, the growing degree day model has improved the R2 for simulations of FFD, EFD, and FD. Overall, this study provides a basis for a better understanding of flowering phenological responses to climate change and simulation of flowering phenology.
Investigation of geochemistry of surface water is a fundamental study of the regional environment in ungauged areas. Also the study is helpful to determine the relationship between hydrological processes and environmental factors including the climate change and geologic structure. Sampling of the lake and river waters in the northern-central parts of Mongolia was carried out in 2013 and 2014. Then, using the measured chemical data of water solutes, the ion compositions and its controlling factors were analyzed preliminarily. The traditional methods in geochemistry, such as Gibbs correlation analysis and Stoichiometry, were applied in this study. Results indicate that the waters in the study area are from slightly alkaline to alkaline. The average value of total dissolved solids in river waters is about 114.0 mg/L, which presents a significantly different spatial variation of ion compositions in river waters. However, generally Ca2+ and HCO3- are the dominant ions in the surface waters in the study area. The most important source of the solutes in the surface waters is rock weathering process. In particular, the contribution of carbonate and sulfate minerals weathering are the largest. Although the current water quality is in a good situation in the northern-central parts of Mongolia, an accumulating trend of the nitrate in waters has been detected. Therefore, great attention should be paid to the influence from the anthropogenic input.
