The problem of grain shortages has long plagued the Tibetan Plateau, therefore both the state and the local government are scaling up efforts to achieve grain self-sufficiency and grain security in this region. Meanwhile, many researchers devoted themselves to study the grain security issues to provide rational advices. Here in this paper, we intended to analyze the temporal and spatial characteristics of grain production and consumption in the Tibetan Plateau and then evaluate the risk status of grain security in 114 counties. First, we revised the standards of per capita grain consumption demand in pasturing area and farming-pastoral region. Then, on this basis, we analyzed the corresponding data of the 114 counties during 1985-2015 by applying the fluctuation coefficient method, classification method, barycenter model and the index model of grain shortages. Analytical results showed that there was a non-uniform geographical distribution of grain production and consumption, moreover, the holistic status of grain security in the Tibetan Plateau was not optimistic. (1) The production of grain increased in fluctuation and the consumption of grain grew steadily, the local grain production could not meet the consumption demand, and the deficit amounts were between 0.21 and 1.22 million tons annually, which accounted for between 8.22% and 40.11% of the grain consumption. The gap between grain production and consumption including tourists increased to 1.33 million tons in 2015. (2) The spatial distributions of grain production and grain consumption in the Tibetan Plateau were imbalanced, the grain yields in Huang-Huang valley and the valley along the?Yarlung?Zangbo?River were higher, while the yields distributed in the central and western parts of the plateau were lower. Affected by population, city, and traffic distribution, the grain consumption was high in the eastern part and low in the western. (3) The spatial patterns of grain security in the Tibetan Plateau in 2015 showed that the higher-risk types involved 42 counties with a population of 2.92 million, and they were widely distributed in western Tibet, northern Tibet, southern Qinghai, Qilian Mountains, as well as in municipal districts of cities of Lhasa and Xining; compared to 1985, the risks of grain security on the midstream and downstream of Yarlung Zangbo River and southeastern Qinghai province were mitigated, while those in western Ngari and northeastern Qinghai were intensified. (4) The tourists increased the risks of grain security in Lhasa, Nyingchi, Shannan, Shigatse, Haidong and Hainan cities, and the negative influence of tourist on Linzhi city was most significant. (5) Production increase alone cannot solve the problem of grain shortage, so it is urgent for the Tibetan Plateau to improve the grain reserves, transportation facilities and expand the grain trade with other regions to achieve regional grain security.
The land use function transition is an important measure to promote the coordination of land use functions and achieve sustainable regional development. This paper constructs an analysis framework for land use function transition based on sustainable development from the perspective of functional coordination, and uses the five phases of remote sensing images of Jiangsu province in 1995, 2000, 2005, 2010 and 2015, as well as related resource utilization and socio-economic data to construct the three level evaluation system of land use function. Taking the county as an evaluation unit, through triangle model and spatial correlation analysis, the spatial-temporal evolution characteristics of land use functions are quantitatively analyzed, and the coordination status of land use functions is proposed for sustainable land use in Jiangsu province. This paper has obtained the following main findings: (1) During the research period, the overall level of land use function in Jiangsu province has increased at a slower pace. The production and living functions have enhanced in different degrees, and the ecological function has significantly been reduced. (2) The spatial aggregation of production and living functions of land use in this province has not been obvious, and the areas of ecological functional hot spots and cold spots have a "Y"-shaped pattern of agglomeration distribution. (3) The sustainable development of different functional areas has not been the same. The sustainable development of key development zones and restricted development zones has been generally good. The sustainable development of optimizing development zones has been weak and continued to deteriorate. In the process of implementing development plans and space planning, we suggest that priority should be given to construct the modern demonstrative region in Southern Jiangsu, the key development zones should be focused on the living function transition, the restricted development zones (I type) should be focused on the production function transition, and the forbidden development zones should be implemented strictly to protect the environment.
In order to improve the interpretation precision of the medium resolution satellite image, this paper proposed a new extraction approach of land use information combining Object Based Image Analysis (OBIA) with Random Forest (RF). Using the Landsat 8 OLI image and according to the features of all kinds of ground objects, the image objects were created combined with the multi-threshold and multi-resolution segmentation method, and the rule set and classifier were collaboratively used in the image classification. The Relief F algorithm was used to dimensionally reduce the spectral, texture and all feature variables, and to select 3 feature subsets. Then the RF model was conducted with the 3 feature subsets and all feature subset to build 4 models. The 4 models were applied to extract land use information in Longkou city, and the results were compared. The result indicated that the OOB (Out of Bag) misclassification, classification accuracy and Kappa index were 0.0958, 89.37% and 0.872 respectively with the land use information extraction approach combining OBIA with RF, dimension reduction based on the Relief F algorithm only for texture features. This retained the complete spectral, geometric and spatial features, which has a higher accuracy. The approach can be applied to the extraction of land use information with the medium resolution satellite image.
Fragmentation of cultivated land will lead to the reduction of agricultural production efficiency, the decline of land use sustainability and the shortage of cultivated land. Land consolidation is one of the important ways to improve the fragmentation of cultivated land in China. In order to explore suitable land consolidation model to solve the problem of optimal allocation of cultivated land resources, this study constructs a model of optimal allocation of cultivated land resources based on multi-objective linear programming model from three aspects: engineering design, ownership adjustment and plots allocation, and selects a typical land consolidation project for case analysis. Then it compares the model optimization and actual land consolidation results with the pre-consolidation from the aspects of agricultural production consumption, improvement of arable land morphology and location, and ownership status. The results show that: (1) Through the optimization of the model, the agricultural cost in the project area, the average number of plots per farmer, and the average cultivation distance decreased by 20.41%, 34.92%, and 68.17%, respectively, while the average size of the plot increased by 53.72%. The fragmentation of cultivated land is reduced and the agricultural production efficiency is improved. However, compared with the typical foreign land consolidation project, there is still much room for improvement in the allocation of cultivated land. (2) The current land consolidation methods have played a positive role in increasing the average size of plots and improving the shape of plots. However, there are still deficiencies in reducing the farming distance of farmers, increasing the adjacency of cultivated roads, and promoting the concentration of cultivated land property rights. (3) Combining land consolidation with land ownership adjustment plays an important role in reducing the agricultural production consumption caused by land fragmentation and inconvenient farming and improving agricultural production efficiency. The research is of significance for enriching planning and designing methods of land consolidation and promoting the solution to the issue of fragmentation of cultivated land.
The economic growth and urbanization development of Nanchang have been accelerated significantly and considerably by China's rapid urbanization and industrialization since the reform and opening-up in the late 1980s. However, due to the rapid urban expansion, the ecological and environmental problems caused by the fragmentation of green landscapes have become more serious. Thus, this paper chose Nanchang city as an example to analyze the changes and relationship of urban expansion types and ecological landscape types, which will provide guidance for improving the ecological environments. Firstly, this paper used the Landscape Expansion Index (LEI) to identify the expansion models of the three periods, and analyzed the variations of construction land expansion from both time and space, based on the land use data of 2000, 2005, 2010 and 2015. Then, the Morphological Spatial Pattern Analysis (MSPA) method was used to obtain the ecological landscapes of the four periods, and expressed the ecological landscape fragmentation process from nine representative points. Finally, multiple buffer layers were created to explore the correlation between the variations in different expansion types and landscape types. The results are shown as follows. (1) Edge-expansion is the main expansion pattern, while ecological landscape is dominated by "core", and the variation of expansion types and landscape types varies with time. (2) The relationship between urban expansion types and ecological landscape types in different circles is significantly different at different development periods. (3) During the urban expansion process, infilling expansion is the main method to improve the compactness at the central urban area. In general, the ecological landscape is more fragmented, the edge-expansion will accelerate the reduction of large green patches, and the outlying expansion promotes the green landscape units more fragmentary, while infilling expansion has the effect of weakening the process. According to the research results, calculating the landscape expansion index of the newly approved construction land and studying the current situation of ecological landscape types will enable decision makers to identify the urban expansion trend and make scientific and developmental predictions for the next stage of development. Then, decision makers can control the disorderly urban sprawl from a macroscopic level.
Scientific and reasonable marine eco-compensation standard has great significance in optimizing the allocation of marine resources and maintaining the sustainable development of the marine economy. Taking the famous aquaculture reclamation project of Shuhutu in Xiangshan county of Ningbo city as the research object, the paper constructed an index system of ecological services value damage assessment, and methods for assessing the recovery capacity of sea areas and the impact cycle of resources. The damage value and characteristics of various ecological services caused by the aquaculture project were calculated and analyzed. The eco-compensation standard and the recovery cycle of the aquaculture project based on the marine self recovery capability were determined, and the differences in the compensation standards determined directly from the ecological damage value and based on the recovery capacity were compared and analyzed. The results showed that: (1) The total value of the ecological damage caused by the famous aquaculture reclamation project is 3.189 million yuan/a, and the damage value per unit area is 32000 yuan/hm2·a. Ecological damage is mainly based on ecological services, accounting for 53.54% of the total. (2) In the category of biological resource damage, the primary category is dominated by the value of resource damage, which accounts for 32.92% of the total. In the second category, the biological damage value of intertidal biological is the highest, at 597100 yuan, followed by the damage value of seaweed farming, fish eggs and larvae, both of which have the same damage value accounting for 13.55% of the total. The value loss of benthos and swimming organisms is smaller. (3) In the category of ecological service damage, the primary category is mainly adjustment service value, accounting for 32.56% of the total. In the secondary damage category, the damage value of waste disposal is the highest, reaching 717700 yuan, while the value of recreation and entertainment is also large, accounting for 12.80% of the total damage. The other types have less value loss. (4) The eco-compensation standard of the famous aquaculture reclamation project based on the sea self-reclamation capacity is 2.809 million yuan/a, and the compensation value per unit area is 28200 yuan/hm2·a. The average compensation value to be paid in installments is 1.8068 million yuan/a and the compensation amount per unit area is 18100 yuan/hm2·a. (5) Compared with the compensation standard determined by the value of ecological damage, the total amount of eco-compensation standard based on the recovery capacity of sea areas is reduced by 11.92%, and the unit area is reduced by 11.88%. After the completion of the project, the recovery speed of nearshore intertidal zone will be 4.632 hm2/a. After a total of 12.97 years, the tidal flat near the new embankment will be restored to the baseline level which existenced before the reclamation starting.
Quantifying the impacts of climate change and human activities on runoff changes is one of challenges in hydrology and water resources researches. In order to reveal the impacts of climate change and human activities on the interannual flow of a karst subterranean river system, this study chose a big karst subterranean river in south China, Nandong subterranean river (NSR) as a research area to analyse the interannual variations of precipitation, evapotranspiration and flow based on the data of flow, evapotranspiration and precipitation of NSR from 1972 to 2014. The results indicated that precipitation, evapotranspiration and flow of NSR during the study period showed a fluctuating decline trend, in which the overall declining rates of precipitation, evapotranspiration and flow were 3.14 mm/a, 7.49 mm/a and 0.014×108 m3/a, respectively. Two inflection-point years in the variations of precipitation and flow, 2002 and 2008 were identified through the sequential clustering and Mann-Kendall test methods. The method of slope changing ratio of cumulative quantity was adopted in estimation of the contributions of climate change and human activities to the flow variations in NSR. Considering the influence of evapotranspiration in NSR, the results, with 1972-2002 as the base period, indicated less effect from human activities. The contribution rates of the climate changes to the flow changes were -86.68% in the T2 period (2003-2008), and 35.92% in the T3 period (2009-2014), while the contribution rates of human activities were 186.68% in the T2 period and 64.08% in the T3 period. Obviously, human activities were the dominant factor causing the interannual flow change in NSR catchment. Direct water consumption of production and living and the changes of flow processes under the influences of land use/land cover changes exerted a main influence on the interannual flow changes. The results can give us a better understanding of the variation characteristics under the impacts of climate change and human activities and help to reasonably regulate karst water resources.
Taking Yuexi county, the core area of Dabie Mountain, which is a focus in China's targeted poverty alleviation campaign, as the research unit, and based on remote sensing and GIS platform, we selected ten ecological resistance factors, namely, elevation, slope, land use type, vegetation coverage, soil erosion, and distance from tourist spot, industrial land, water area, road, residential areas, to establish an ecological security evaluation index system. With the aid of ArcGIS, ecological security level was evaluated and potential ecological corridor recognition was extracted, through Exploratory Spatial Data Analysis (ESDA) method, Minimum Cumulative Resistance (MCR) model and gravity model, to build ecological resistance. The results showed that: The high and higher level regions accounted for 37.79% of the total area of the county, while the low and lower ranking regions accounted for 51.89%, which present the spatial characteristics that the low level ecological security units were distributed in the north part, while the high level ones were in the south part, and that the overall ecological security level was relatively low in the county. Secondly, the spatial distribution characteristics of ecological security by means of ESDA analysis method indicated that the global Moran's I index was 0.6374, and LISA figure showed that there were mainly high (HH) and low (LL) types of aggregation for ecological security level, and the ecological security had a significant spatial clustering characteristic in Yuexi county. On this basis, good habitat in the nature reserve and large scenic spot patches were chosen as the ecological source, which is the first step for ecological source cumulative cost resistance surface generated by cost distance tool of ArcGIS. Then, the minimum cumulative cost path and the potential ecological corridor were identified and constructed based on MCR model. The results showed that a total of 21 important potential ecological corridors and 103 ecological nodes were identified and extracted, including 13 first-level corridors and 8 secondary corridors by means of gravity model. Finally, according to the characteristics of the tourism poverty alleviation industry and ecological economic development in the study area, the paper put forward the layout model of "one ring and three zones" ecological corridor network framework and some optimization countermeasures. This model is an effective supplement to the development pattern of ecological economy industry in Yuexi county.
This paper is mainly based on daily rainfall data from 76 meteorological monitoring stations in the Taihang Mountains and its surrounding areas from 1954 to 2016. A simple model is established to simulate the annual rainfall erosivity based on different magnitudes of aggressive annual rainfall. The climatic trend rate, wavelet period analysis, center of gravity model, Co-Kriging interpolation, Mann-Kendall non-parametric trend test and mutation analysis were used to analyze the spatial and temporal variations of rainfall erosivity and their influencing factors. The results show that: (1) The simple model of annual rainfall erosivity in the Taihang Mountains area is y=0.182x11.095+5.463x20.982+9.401x31.017+15.258x4-26.753, and the erosivity of rainfall over years showed a slight upward trend, and it increased by 2.4 MJ·mm·hm-2·h-1·a-1 in 10 years. There is also a major cycle of about 20 a and a small cycle of 6 a, and significant mutations occurred in 1996. The eclipse of moderate rain and heavy rain showed an upward trend in 63 years, while the violent rain and extraordinary rainfall erosivity showed a downward trend. The spring and autumn seasons are mainly affected by moderate and heavy rain erosivity, while summer is mainly affected by excessive rainfall erosivity. (2) The maximum rainfall erosivity of all magnitudes is mainly distributed in the southeastern part of the Taihang Mountains and the Wutai Mountain areas. The minimum is mainly distributed in the northeastern part of the study area. Using the center of gravity model, we found that the gravity center of each magnitude of rainfall migrating migrates to the east and northeast in spring and summer, while that of the autumn and winter seasons migrates to the south and southwest, forming a cycle that is consistent with the control time of the winter and summer monsoons. (3) There was a significant positive correlation between rainfall erosivity and erosive rainfall in different magnitudes in the Taihang Mountains (P<0.01). Heavy rain and extraordinarily heavy rainfall erosivity were significantly negatively correlated with latitude and altitude (P<0.05). This is mainly related to factors such as subtropical high pressure movement, topography, elevation and natural geographical environment.
The Sawuer Mountain spans the two countries between China and Kazakhstan and is the transitional section between the Tianshan Mountains and the central Altay Mountains. This mountain range is not only the most obvious watershed for the inland and Arctic sea systems in Xinjiang, but also the highest mountain in the northernmost part of the western Junggar Basin. Muz Taw Mountain is the main peak of the Sawuer Mountain and Muz Taw Glacier in the peak is the most important tourist resource in Jimunai county. The northern slope of the study area runs through a glacier snow-fed river, the Ulejkururasu River, which is also a boundary river between China and Kazakhstan. Glaciers, as the alpine solid reservoir, whose river runoff by ablation plays a very important role in the survival and development of agriculture and livestock husbandry in the middle and lower reaches of arid regions. Meanwhile, glaciers also affect the sustainable development of ecological environment and social economy in a large extent. Therefore, it is possible to predict future changes in the glacier and the future development of the area affected by the glacier via understanding the changing trends of glaciers and their response to climate change. Based on the Landsat 1977 MSS, 1989 TM, 1998 TM, 2006 TM and 2017 OLI / TIRS remote sensing image data, the glacier information of five periods in the Uighur region was extracted by visual interpretation and GIS technology. The trend and periodicity of temperature and precipitation were analyzed to investigate the response of the glaciers to climate change in recent 40 years in the region. The results show that: (1) From 1977 to 2017, the total glacier area in the study region decreased by 10.51 km2, retreating by 45.72%, and the retreat rate was 1.14%·a-1, with the glacier retreating at an accelerating stage. (2) The smaller the glacier scale, the faster the retreat speed; (3) The south slope retreats fastest, followed by the southeast slope and the southwest slope, and the slowest retreat is in the northeast slope, and the gradient of the glacier shrinkage at 5°-40° generally shows a trend of increasing with the increase of the slope; (4) The study region is in the period of temperature rise and precipitation increase, and the increase of precipitation cannot make up for the glacier ablation caused by the temperature increase, leading to the accelerating retreating rate of glacier. (5) Compared with the glaciers dominated by other factors, the glacier retreats. More glaciers with higher retreat rates and smaller areas is another factor in forming this result.
The evolution of the rural production space system is the representation or result of the exchange of material, energy and information within and out of the rural production space system. The pros and cons of this result is the endogenous material basis and guarantee which can realize the sustainable development of the system. This study sets Chongqing as the research area with a research period from 2001 to 2015 and establishes the index system of rural production space system evolution from four aspects of support-type input entropy, pressure-type output entropy, oxidation-type metabolism entropy and deoxidization-type metabolism entropy based on information entropy. The study reveals the evolution law and sustainable development capacity of rural production space system, analyzes the relationship between entropy change and sustainable development capacity of rural production space system in the process of co-evolution, and designs the optimal path for rural production space system. The results shows that: (1) From 2001 to 2015, the entropy flow of rural production space system in Chongqing is from 0.017 to -0.049 and the entropy production is from 0.204 to 0.059, which shows a downward trend; and the coordination and vitality of rural production space system are enhanced. The total entropy change is from 0.221 to 0.010, showing the same trend; the degree of order in rural production space system keeps improving, and generally, it is developing towards a healthy level. (2) From 2001 to 2015, the score of sustainable development capacity of rural production space system in Chongqing is from 1.285 to 2.803, showing an upward trend. The sustainable development of the system is in a good state and is evolving towards the sustainable direction. (3) The score of sustainable development capacity is positively correlated with support-type input entropy and deoxidization-type metabolism entropy, negatively correlated with pressure-type output entropy and oxidation-type metabolism entropy, and negatively correlated with entropy flow, entropy production and total entropy change.
Understanding the spatial and temporal variations of crop yield and soil nutrient can optimize the agricultural resources utilization and sustain the agro-productivity, which is of great significance for agricultural production activities. In this study, the quality monitoring data of crop yield and soil nutrients were used to analyse the evolution of crop yield and the spatial distribution of soil organic matter and other nutrients in the irrigated area at the lower reaches of the Yellow River in the North China Plain. The results showed that there were significant spatial and temporal differences in the level of agricultural productivity within the irrigated area. Since the late 1980s, the overall level of farmland productivity had been on the rise. The high yield field of winter wheat was distributed in Qihe county in the north part and the three counties in the south part of the lower reaches of the Yellow River with a range of 6084.0-6861.0 kg/hm2. The spatial distribution of summer maize yield showed that the intermediate area was higher than the two sides, and the yield of Qihe county was the highest with the yield of 7524.0 kg/hm2. The lowest yields of winter wheat and summer maize were found in Dongying county, which were 4705.5 and 5092.5 kg/hm2 respectively. The distribution of organic matter and nutrient of farmland in the irrigated area had obvious spatial and temporal differences. The highest organic matter content and available potassium were observed in Dezhou, being 16.30 g/kg and 202.40 mg/kg, respectively. The highest total nitrogen content was in Zibo, being 1.17 g/kg. The highest phosphorus content was in Tai'an, being 34.56 mg/kg. However, the lowest contents of organic matter, total nitrogen and available phosphorus were observed in Dongying, being 9.90 g/kg, 0.60 g/kg and 19.10 mg/kg, respectively. The results suggested that the level of agricultural productivity in the irrigated area had been continuously improving, which indicated that a great potential of agricultural productivity still exists. In addition, identifying the spatial difference of nutrient distribution can give the guidance to design the reasonable fertilization strategies for precision agriculture, and higher and more stable productivity.
In-situ conservation is an important measure to protect biodiversity. By the end of 2017, China had established 2750 nature reserves, accounting for 14.9% of China's land area, which exceeds the world average. However, management failure is still serious. The effective management of nature reserves requires adequate funding. Based on a thorough study of the cost estimation methods for nature reserves and relevant management standards, this paper develops a conservation cost model of nature reserves, and estimates the management cost and opportunity cost of nature reserves in China. The results show that: (1) The conservation cost of all nature reserves in China is 504.9 billion yuan in 2014, accounting for 0.78% of the national GDP of the year, far lower than the cost of environmental damage and the economic value of the products and services of the nature reserve ecosystem, so the nature reserve system is economically justified. (2) In order to meet the management standards, the nature reserves in China require approximately 8.59 billion yuan annually. But the actual total investment is much lower than the fund request, reflecting overall funding gaps, and the inequality of fund allocation among nature reserves. (3) The management costs show obvious geographical differences. The nature reserves in the western and northeastern regions have high ecological value and large demand for management funds, while the economy is relatively undeveloped and the local financial pressure is relatively high. The national government should give more support to the nature reserves in the western and northeastern regions. (4) The annual opportunity cost of nature reserves in China is approximately 496.3 billion yuan, reflecting the huge economic pressure on the local society. However, the ecological compensation for nature reserves is in short supply. Governments need to improve ecological compensation mechanism for nature reserves to solve the dilemma between nature conservation and the development of surrounding communities.
The shortage of water resources has become a hard constraint to the sustainable development of the arid areas of Northwest China. Increasing the technical efficiency of crop irrigation (TECI) and reducing agricultural irrigation water use may be one of the possible ways to ease the contradiction between water supply and demand. Based on the survey data of farmers in Zhangye city in 2014, this paper uses the DEA-Tobit model to analyze the TECI and its determinants in different types of irrigation zones in the middle reaches of the Heihe River Basin. The results show that there is a certain improvement space of TECI of main crops in the typical irrigation zones. With the other inputs unchanged, if the TECI reaches the current highest level in different types of irrigation zones, in order to produce the same amount of the seed maize and maize, the irrigation water can be reduced by 34.47% and 38.15% in the plain irrigation zone; in order to produce the same amount of the cotton, seed watermelon and maize-wheat (inter-corn), the irrigation water can be reduced by 48.42%, 34.82% and 22.99% in the northern desert irrigation zone; in order to produce the same amount of the wheat, potato, barley and maize, the irrigation water can be reduced by 14.48%, 30.75%, 25.50% and 35.96% in the mountain irrigation zone. In addition, the coefficient of variation of the TECI in different irrigation zones is negatively related to the proportion of cropland area, and there is a significant difference in the production management level of farmers who grow the same crop in the same irrigation zone. What's more, the fragmentation degree of cultivated land and the expansion of cultivated area have negative effects on the TECI in different irrigation zones, improving the quality of cultivated land has a significant positive effect on main crops in the northern desert irrigation zone. Increasing well water irrigation has a positive effect on crops such as maize in plain irrigation zone and wheat, potato, maize in mountain irrigation zone, and there is an inverted U-shaped relationship between irrigation frequency and the TECI. However, the influence of farmers' demand for cultivation and the attitude towards risk need to be judged based on specific conditions. Therefore, determining the production scale, accelerating the optimization and reorganization of cultivated land and improving the quality of cultivated land, rationally guiding the use of well irrigation, and enhancing the water conservancy facility and the flexibility of river water irrigation are the main ways to improve the TECI in the Heihe River Basin.
Coal has been China's dominant indigenous source of energy. Although the proportion of coal consumption in total (primary) energy consumption decreased steadily in recent years, China is still the world's largest coal producer and has been exporting substantial amounts of the energy. Due to a long history of underground coal mining, many more undermined areas have subsided than most people can imagine. Large coal-mine subsidence has resulted in serious structural damage to buildings, roads, irrigation ditches, underground utilities and pipelines. Besides, the consequences of ground subsidence generally consist of serious environment impact and livelihoods issues of residents. All these has drawn a lot of attention from scholars and government leaders. However, it still fails to figure out the whole picture of coal-mine subsidence and its consequences in China. The research has employed a unique dataset of mineral rights for coal in China to investigate spatial distribution of subsidence at present and foreseeable future. The damage to cities and farmland and the size of population involved in the subsidence areas has also been estimated through the comprehensive analysis of land use map and population and subsidence distribution. The results highlight the difference of potential losses of coal-mine subsidence between areas in China. For example, subsidence has significant influence on urban development in eastern China; while farmland in rural areas suffers relatively great loss in the western mountainous areas. Even so, it is not enough to answer how to govern and mitigate subsidence of those large coal-mines in China. Because governance modes and methods depend on not only characteristics of spatial distribution and potential losses but also natural conditions and the level of economic development. According to characteristics of potential losses, natural conditions and economic development, we further define six kinds of subsidence and figure out their governance directions and major works in China. The results are shown in the following: (1) The area of potential coal-mine subsidence is more than 60000 km2 in China. There are 4500 km2 of the urban-rural construction land and 26000 km2 of farmland in these subsiding areas. There are around 20 million residents involved in the subsidence. (2) According to climatic conditions and social and economic development levels, coal-mine subsidences fall into four types of areas with different governance directions in China: Focusing on eco-environmental modification; household livelihood security; exploitation and utilization; migration and relocation. (3) According to population and construction lands impacted and hydrogeological environment, exploitation-oriented areas are further divided into three types: Some should adapt to the changing environment; some should repair the infrastructures destroyed; some should develop characteristic industries such as tourism to increase residents' income.
Due to the difference of statistic standarda and calculation methods, the results of grain self-sufficiency rate were generally quite different and the assessment of the grain security situation in China varied greatly, which aroused great controversy. In order to accurately analyze the grain security situation of China to avoid misleading the relevant decisions, it is necessary to study the grain statistical data sources and the calculation methods of grain self-sufficiency rate. In this work, three commonly used methods, which were the stint counting method, the flow statistics method and the consumption statistics method, were used to estimate and analyze the grain, cereal grain and edible grain self-sufficiency rate in China during 2000-2016. The results were as follows: (1) The stint counting method would cause distortion in the results, while the results provided by the flow statistics method and the consumption statistics method were more accurate. (2) The cereal grain and edible grain self-sufficiency rates could report the actual grain supply demand relations. (3) The self-sufficiency rate of cereal grain was greater than 98%, and that of edible grain was greater than 100%. However, with the acceleration of industrialization and urbanization, city development demand for more land which would cause serious problems such as embezzlement of cultivated land and soaring grain demand, so grain production still should not be slackened in China. It is suggested that the agricultural structure should be adjusted in the future to stabilize the production of wheat and rice.
The rural revitalization, as a national strategy in the new era, puts forward the requirements and goals of the thriving industry, pleasant living environments, social etiquette and civility, effective governance and prosperity. China is a country with a vast territory, marked by regional differences in resource and economic development levels. What's more, rural areas are complex, diverse, and have many problems. Rural revitalization is a systematic project with comprehensive, complex and regional characteristics. Sixteen young scholars in the field of rural geography across the country have conducted in-depth discussions and reflections on the scientific path of rural revitalization in China. The core points are as follows: (1) In accordance with the law of time-space distribution, we should fully understand the connection between the historical basis of rural development and the practical needs, establish a theoretical and technical system that highlights regional characteristics and has operability, and promote the transformation of rural residential environment, industrial system and governance mode in a classified and orderly manner. (2) Rural revitalization strives for the integration between urban and rural areas to build a compound multi-center network system, which breaks through the village and town systems of traditional linear "central place", and innovate the spatial organization mode of "village cluster". Rural endogenous force, urban radiation force and planning binding force jointly drive rural revitalization. (3) The agriculture has multiple functions such as food safety, social stability, and ecological products. Its development needs to create the whole value chain of agriculture to promote the integration of primary, secondary and tertiary industries. (4) In energy-rich areas, we should fundamentally solve the problem of unbalanced and inadequate rural development under the premise of ensuring the national energy security demand. In Southwest China, we should take advantage of ecology and human resources to build a modern agricultural industry system, remodel the brand of rural tourism, and build landscape rural homes. In Northeast China, rural revitalization must proceed in an orderly and classified way in the process of synergistic promotion of the "northeast revitalization" strategy. In the Yangtze River Delta region, it is necessary to cognize the evolutionary stages from rural industrialization to rural urbanization, and then to rural characteristics with more and more emphasis on the social, cultural and ecological construction of rural areas, seeking a scientific path of rural revitalization. In Northwest China, we propose to effectively improve the ability of "independent poverty alleviation" in rural areas under the premise of ecological protection, and realize the transformation from "transfusing blood" to "producing blood". In the Beijing-Tianjin-Hebei region, oriented by equalization of basic public services in urban and rural areas, we will promote the development of urban-rural integration and rural revitalization. In resource-oriented areas, rural industries will replace the industrial system formed around resource exploitation with an efficient agricultural system integrating primary, secondary and tertiary industries. In traditional agricultural areas, it is necessary to optimize the coupling pattern between farmland use transformation and rural labor structure change, which is an important means to achieve rural revitalization. In economically developed areas, villages with "mixed" characteristics need to activate the assets and capital attributes of rural land resources, promote the integration and activation of spatial order, and comprehensively explore the modern rural governance mode with the participation of multiple subjects.
