Comprehensive suitability evaluation of spatial development and construction land is the scientific basis and guarantee for optimizing spatial development pattern and improve its quality and efficiency. It is of great significance for the implementation of regional coordinated development strategy. In this paper, according to the principles of urban-rural integration and land-ocean co-ordination, we selected Liaoning province as a case, the only both coastal and border province in Northeast China. The suitability evaluation index system was established from 3 dimensions, including natural environment, economy and society, and marine function. To evaluate and analyze the suitability of spatial development and constructive land in this province, we integrated the application of Delphi method, cask theory, linear weighted summation model and multi-factors space overlay analysis. The results show that there exist obvious characteristics of spatial differentiation in the suitability of spatial development and construction land throughout Liaoning. The most and more suitable construction land represent an obvious central peripheral structure, and concentrate along both the Shenyang-Dalian axis and the Binhai axis; the most unsuitable construction land shows a north-south symmetric distribution by the Binhai axis, while the more unsuitable construction land shows an east-west symmetric distribution by the Shenyang-Dalian axis. The construction land areas of most suitability, more suitability, more unsuitability, and most unsuitability are 15504.39 km2, 22645.34 km2, 66833.96 km2, and 68720.99 km2, respectively, and the proportions of land-ocean area are 8.93%, 13.04%, 38.48%, and 39.56%, respectively. The suitability of natural environment plays a fundamental and decisive role in the development and construction of regional land; and the characteristics of agglomeration and dispersion are significantly different at different levels and regions. The suitability of economy and society obviously modifies that of natural environment. The introduction of marine functional zone has greatly expanded the regional land in Liaoning province, but the spatial distribution of marine functional suitability is extremely uneven. And due to the nature of marine functional zone, the space which can be directly developed and constructed is limited, while the space for protection is great. The contradiction between spatial development and ecological environment protection will be still severe for a long time.
Grain reserves are of great significance to the maintenance of food security and social stability. Recently, the gap between the time and space in production, supply, and demand of grain in China has been continuously increasing, which leads to the unreasonable regional grain reserves scale problems of China. Taking province as research unit, this paper analyzed the temporal evolution and regional differences of regional grain reserves by utilizing spatial exploratory analysis and dissected influencing factors of regional grain reserves scale through spatial econometric model. It provided a definite method of regional grain reserves scale for different sub-regions. The results showed that: China's grain reserves spatial correlation index is bigger than zero and increased year by year, indicating that different regional reserves scales have significant positive spatial correlation. The overall distribution of China's grain reserves shows a polarization from east to west and has undergone a significant spatial-temporal evolution with high reserves area expanding to the northeast and low reserves area transferring to the west, which caused the increasing regional differences. Regression analysis shows that the scale of regional grain reserves is closely related to grain production capacity, population size, economic development, disaster influence, transportation conditions and social influence. The regression coefficient of the spatial lag term was 0.2451, manifesting that the geographical positive spatial correlation of regional reserves scales transmits through adjacent areas. Based on this, this paper put forward the prediction range of regional grain reserves scale in 2020 by considering the spatial effect and correlative factors, which provides a new perspective for researches on regional grain reserves in China.
As the economic development of China enters into a new normal, coal industry is changing greatly. To reduce the total cost of the coal supply industry in China and calculate the carbon emission of it, we developed the R-CSSM model based on linear program method to optimize the future pattern of China's coal production and transportation on the basis of the collection and analysis of the present situation of the coal supply industry and relevant policy. The carbon emission coefficients were calculated after we examined each link of the coal supply industry in different regions. Then we used these coefficients to calculate the carbon emissions from coal related activities under the optimized pattern. The results show that, under the existing arrangements and the constraints of resources and policy, China's coal production will continue to be centralized, the coal production of Shanxi, Shaanxi, Inner Mongolia, Ningxia, Gansu and Xinjiang will continue to rise, accounting for nearly 88% of all coal production in China by 2030, and this ratio rises by 17% compared with 2015. The pressure of coal transportation would increase first and then decrease, the railway transportation ability of Xinjiang, and southwestern and northeastern China for coal will be low, and railway expansion and reconstruction project need to be taken in these places. By 2020, the coal supply industry would have a total emission of about 641 million tons of carbon dioxide-equivalent, compared with 2015, and emission per unit of supply will fall by 8.75%. And the coal supply industry would have a total emission of about 526 million tons of carbon dioxide-equivalent in 2030, compared with 2015, emission per unit of supply will fall by 15.34%. Based on that, the coal production capacity, the coal transportation capacity, and the carbon emissions of coal supply industry in each province were analyzed. And the relevant suggestions for the development of China's coal industry have been put forward, which can provide a good support for the related decision making and the carbon emission reduction of coal industry.
Based on the statistical data from 1990 to 2016, this paper uses field theory to study the changes in the temporal and spatial pattern of coal resources in the world and their causes, revealing the flow of the world's coal resources and their evolution in the past 30 years. The results show that: (1) In 2016, the world's coal output reached 1.225 billion tons, an increase of 1.013 billion tons over 1990 and the average annual growth rate is 6.98%. Among them, Australia, Indonesia and Russia are the main exporters of coal, while India, Japan, China and South Korea are the main coal importers. (2) Analysis of the potential of the field theory, the distribution of the flow field and the angle of the flow trace, the flow of world's coal resources is the source flow in North America, Central and South America and Africa, with Europe and Eurasia, the Middle East and the Asia Pacific as the sinks flow field, and the major transport routes between Australia to East Asia, Indonesia to East Asia and India. (3) Spatial distribution of resources, matching degree of supply and demand, space distance, market factors and national policies are the main reasons for the flow of coal resources. The study found that although China's coal reserves are abundant, the amount of coal consumption is huge, and it can last for only 72 years, so we must attach importance to the import and storage of coal. This study is of great value to China in formulating industrial policies scientifically.
The traditional methods for allocating the quota of newly-added construction land have many deficiencies. For example, the research perspective is single and the administrative force intervened severely. This paper, based on the idea of fairness and efficiency, uses some rules of solution to bankruptcy model to allocate the quota of newly-added construction land in Zaoyang city of Hubei province, and applies digraph game theory to compare various results of the allocation creatively. The basic data of the case analysis come from "The Outline of the General Land Use Planning in Zaoyang city (2006-2020)" and its related research papers. First of all, the total demand for newly-added construction land in the whole city in 2020 is predicted to be 3976.66 hm2 by using the polynomial model that is based on the data of the construction land during 1996-2005. Secondly, the requirements of 16 subordinate administrative districts were determined by the analytic hierarchy process and entropy weight method, and then, a total of 2147.09 hm2 of newly-added construction land was decomposed among the subordinate districts by six rules of solution to bankruptcy model. Finally, the characteristics of various allocated schemes are analyzed according to the digraph game method. The concept corresponding to fairness and efficiency is balanced development and unbalanced development. Different stages and regions may follow different development ideas in practice of the general land use planning. The research results show that: (1) The proportional rule and the Piniles rule accord with the proposition of "fairness priority", which is applicable to the balanced development strategy in the development stage and region of relatively developed economy; (2) The constrained equal losses rule and the Talmud rule accord with the idea of "efficiency priority", which is applicable to the unbalanced development strategy in the development stage and region of relatively backward economy; (3) The constrained equal awards rule and the constrained egalitarian rule are applicable to the key support strategy in poverty-stricken areas. The new method not only avoids the problems caused by traditional methods, but also provides some choices for regional development strategy. The new method proposed in this paper can not only be used in new round of the general land use planning, but also be widely used in the distribution of public resources.
It is of significance to analyze the temporal and spatial evolution of karst valley of farmland so as to reveal the law of human-environmental relationship in the karst valley rural area, with Yinjiang county as an example, which was divided into trough valley region, low mountain valley region, Fanjing mountain region and hilly valley region. Based on the landform, multi-source data are used to discuss the change of cultivated land quantity and its distribution evolution at different elevations and on different slope scopes from 1958 to 2016 in the county. The results show: (1) Farmland increased first and then declined; woodland increased after decreases. Before 1990, woodland was transferred to farmland, but after 1990, cultivated land was transferred to forest, and the degree of transfer of each subregion was different. (2) The fluctuation elevation level of cultivated land is 700 m. When it is lower than 700 m, it expanded before 1990 and then shrank, the range of change decreased as the elevation increased. Above 700 m, the fluctuation was not obvious. (3) Taking 1990 as the boundary, the cultivated land expanded before 1990 and shrank after 1990 on all slopes. If the slope is less than 25° slope, the farmland increased with the increase of slope. Within the slope greater than 25°, the cultivated land decreased with the increase of slope. (4) The fluctuation of cultivated land in the study area was closely with the land dependence of local farmers. Cultivated land will expand, if farmers are highly dependent on land. On the contrary, the cultivated land will shrink.
Scientific division of urban development space and agricultural production space is an important way to solve the problems of unregulated urban development and food security. Taking Linchuan district in Jiangxi province as an example, this paper uses ArcGIS, GeoDa software and others to establish a preliminary demarcation of the permanent basic farmland based on the comprehensive quality and autocorrelation of cultivated land in Linchuan district, and uses a multi-criterion CA model to simulate urban expansion. Through the comparison and adjustment of the results of the two aspects, combined with the direction of urban development, urban development model and the farmland natural utility grade, the demarcation of the boundary between the permanent basic farmland and the urban development will be carried out. The results showed that the demarcated area of permanent basic farmland was 593.46 km2. The preliminary delimitation results were mainly distributed in Shangdundu town, Chonggang town, Hejian town, Rongshan town, etc. The comprehensive quality of cultivated land was high, and most of it was high-high gathered area. According to the results of urban expansion simulations, the area of urban construction land in Linchuan district has increased significantly, and the area mainly increased in Zhanping township, Shangdundu town, and Zhongling street. The results of urban development direction analysis and urban expansion model analysis show that the urban construction land in Linchuan district mainly expands to the northwest, southeast, and southwest, and the expansion type is mainly a spreading one. According to the farmland natural utility grade, the initially demarcated permanent basic farmland is divided into an adjustable-in area and an adjustable-out area, so that the optimization and coordination of the permanent basic farmland area and the urban development boundary are carried out, and the final results are obtained between the permanent basic farmland area and the urban development boundary. It is predicted that the boundary area of urban development will reach 142.59 km2 by 2030, with a difference of 4.21 km2 out of a total of preliminary delineation of permanent basic farmland area. The research results can provide reference for the protection of cultivated land resources and avoid the disorderly expansion of cities, and can also provide reference for the future delineation work.
Under the background of Sloping Land Conversion Program (SLCP), this study explores the temporal variation characteristics and the correlation and heterogeneity of spatial transfer of the ecological service value (ESV) for different land use types of Yan'an, a city with remarkable ecological improvement after the SCLP. To achieve this goal, the ESV of different land use types at a grid scale of 2 km × 2 km is calculated using land use transfer matrix achieved from the interpreted image data of three periods and exploratory spatial data analysis (ESDA). The results show that: (1) From 1990-2015, the increase (decrease) of ESV mainly occurred between arable lands, forests and grasslands, and the total ESV increased from forests and grassland was 2.129 billion yuan, the amount of transfer-in mainly occurred after the implementation of the SLCP; (2) The ecological service function was mainly provided by forestland and grassland, the ESV experienced a process of descending and then increasing from the temporal perspective, and the implementation of SLCP promoted the growth of ESV with an increase of 5.34% during 2001-2015; (3) The ESDA shows that, the ESV has a significant distribution of "high in the south, while low in the north" pattern at the grid scale which expresses positively spatial agglomeration and dependence, and it is obvious that the high-high aggregation area accorded with the spatial distribution of forestland and grassland whereas the low-low aggregation area accorded with that of farmland and construction land. Overall, the transfer of land use types and the changes of ESV in Yan'an city coincided with the implementation of SLCP temporally and spatially, which indicates that the SLCP, a government-dominated project, had a significantly positive effect on the restoration and protection of ecological environment. Therefore, with regard to the ecological service function of different land use types, the northern part of the study area with a large amount of cultivated land should pay attention to the balance between agricultural production and ecological benefits based on the basic farmland protection system, while the southern part with abundant forestland and grassland should continue to play a critical role in the regulation function of ecological barrier.
The economic value of irrigation water is an important basis for the pricing of irrigation water. Based on farmers' data in Shaanxi Guanzhong irrigation area, this paper applied Residual Value Method to calculate the economic value of irrigation water for wheat, corn and apple. The results show that the economic values of irrigation water for the three crops are 0.66 yuan/m3, 0.84 yuan/m3 and 3.17 yuan/m3, respectively. Taking the results as the upper limit of irrigation water price and compared with the current irrigation water price, we found that the water price increase range of wheat and corn is between 0.24-0.71 yuan/m3. The apple water price adjustment space is relatively relaxed, ranging from 2.72 to 3.04 yuan/m3. Furthermore, the analysis of factors influencing economic value of water based on quantile regression shows that the main factors are family economic level, type of crops, and whether to carry out comprehensive reform of agricultural water price project. The educational level, family economic level, farmers' subjective cognitive characteristics, and whether to carry out the comprehensive reform of agricultural water price project are positively correlated with the economic value of water, while age, non-agricultural occupations, number of non-farm labor forces in family, land quantity and water economic value are negatively correlated with it. Specifically, (1) when economic value of irrigation water is at low stage, the characteristics of farmers and families as well as the farmland dispersion have significant impact; (2) when the economic value of irrigation water is at high stage, raising farmers' water-saving consciousness and joining water users association will be able to effectively improve the economic value of irrigation water; (3) the conversion from grain into cash crops and the comprehensive reform of agricultural water prices have significant positive effects on all quantile points. This paper provides the basis for the agricultural water pricing classification in Guanzhong irrigation area, and also shows a new perspective for calculating the economic value of irrigation water.
As an important part of streamflow and water cycle in a watershed, base flow can not only provide reliable water supply but also maintain healthy watershed ecologically and environmentally. It is of great significance to divide the base flow accurately from the measured streamflow and to analyze its variations for understanding the dynamics of base flow changes and managing water resources. We used the measured daily streamflow data from Daning Hydrological Station of Xinshui River Basin (3992 km2) located on the Loess Plateau of northern China, climate data measured by meteorological stations and raingauge stations located within and in the vicinity of the basin from 1955 to 2015 and the GIMMS-NDVI data to explore the dynamic changes of base flow. Base flow partitioning was conducted by using digital filtering method (3 times, α=0.925) from the daily streamflow data. Mann-Kendall test, Pettitt test, wavelet analysis and Hurst test were performed to explore the base flow changes in the aspects of trend, turning point, periodic behavior, and sustainability at annual scales. Averaged annual base flow from the basin was 45 million m3 and the base flow index (BFI) was 0.368 between 1955 and 2015. There were significant decreasing trends for yearly base flow (P<0.01), with the turning points occurring in the year of 1985. In addition, a 27-year periodical cycle was observed for annual base flow. It was predicted that the annual base flow will be further reduced in the future as indicated by a positive correlation between historical change and the future regime (H>0.50). Double mass analysis indicated that climate variability and human activities have contributed to a significant decrease in base flow. Precipitation was the major climate factor rather than temperature, which caused the decrease of base flow. The base flow is divided into three stages by the double mass curve method. Human activities affected the base flow by changing vegetation coverage, exploiting groundwater, mining coals and taking measures in soil and water conservation. Compared with the first stage, the proportion of precipitation and human activities in the second and third stages was 25.89%, 74.11% and 0.37%, 99.63%, respectively. There has been an increased impact of human activities on the decreased base flow since the beginning of the 21st century.
Studying the law of spatiotemporal evolution of agricultural total factor productivity is of great significance to formulate the agricultural transformation and upgrading policies rationally. This paper, which is based on the calculation of agricultural total factor productivity growth from 37 counties in Chongqing over the period 2000-2016 by using DEA-Malmquist index model, investigates characteristics of spatiotemporal evolution of agricultural total factor productivity by using spatial analysis and Kernel density estimation methods and identifies the problem regions of Chongqing. The results are listed as follows: (1) From 2000 to 2016, the agricultural total factor productivity is on the rise. The agricultural total factor productivity index has a tendency of "U" type and periodic fluctuation, which shows obvious spatial imbalance. (2) The change trend of agricultural total factor productivity index is similarly consistent with that of technical progress index, which indicates that the technology progress is the main reason for total factor productivity growth. (3) From the view of the whole city, the Kernel density curve of agricultural total factor productivity keeps moving to the right, and the crest height continues to rise. The crest shape changes from "unimodal" to "multi-modal" distribution, which implies that the regional disparity of agricultural total factor productivity shows an increasing trend during the study period. (4) According to the relationship among agricultural total factor productivity growth, technical progress and technical efficiency, three types of problem regions are identified. Then policy suggestions for agricultural transformation and development are proposed for each type of problem region.
As industrial agglomeration increases, wastewater, waste gas, and solid waste are becoming the main sources of environmental pollution. Therefore, how to correctly deal with the relationship between industrial agglomeration and pollution emissions has become a hot issue in the current academic circles. Agglomeration externality is an important mechanism to reduce industrial pollution emission, and different agglomeration modes correspond to different pollution emission behaviors. Therefore, this study divides agglomeration into four types such as specialization, diversity, related diversity, and unrelated diversity. The research goal of this paper is to investigate the effects of different agglomeration types on pollution emissions. Taking 31 provincial units in China as an example, based on the theory of agglomeration economy, this paper analyses the characteristics of industrial pollution in China and studies the relationship between industrial agglomeration and different industrial pollution. The main conclusions are as follows: (1) There is a significant spatial difference in the intensity of industrial wastewater, waste gas and solid waste. Generally speaking, the discharge intensity of industrial wastewater in the Yangtze River Basin is higher, and that of the northwest and southwest regions are rising significantly. The emission intensity of industrial waste gas and industrial solid waste in the north and northwest regions is higher. (2) Diversity is more beneficial to the reduction of emission intensity of industrial pollution than specialized agglomeration. Diversity has the greatest impact on industrial waste water, and has little effect on the gas and solid pollution. Industrial linkage is an important condition for diversity agglomeration to produce environmental 'self-purification' effect. Related diversity is conducive to the decrease of emission intensity of industrial pollution, and unrelated diversity will exacerbate pollution levels. (3) From the perspective of different polluting industries, the specialized wastewater pollution industries is conducive to the decline of pollution intensity, while the specialized waste gas and solid waste pollution industries will intensify pollution emissions. The diversified development of the polluting industry is conducive to the decline of pollution intensity. (4) The effects of different agglomeration types on industrial pollution are heterogeneous in terms of regional and pollution types. (5) To further reduce industrial pollution, we should improve the diversity of the agglomeration industry. We should also pay more attention to the improvement of the inner correlation between the industries and avoid the spatial concentration of the unrelated industries. At the same time, differentiated prevention and control measures should be formulated according to different regions, polluting industries, and industrial pollutants.
The security of land use change is one of the important criteria for evaluating sustainable land use. The study takes Huajiang, Hongfenghu and Yachi rocky desertification control areas as examples, evaluates the security of land use change of rocky desertification control areas based on the "vertical-and-horizontal" method, and provides reference for evaluating the impact of land use change on rocky desertification and improving the land use pattern in the study areas. The results show that: (1) Land use change in the rocky desertification control areas is evident. The proportion of land use change in Huajiang, Hongfenghu and Yachi is 2.85%, 3.34% and 37.88%, respectively. Forest and construction land increased, while farmland and unused land decreased. (2) The comprehensive security and ecological, economic and social securities of land use change in different areas are different. The comprehensive security of Huajiang and Hongfenghu rose by 1.44% and 0.46%, while that of Yachi declined by 1.9%. In the Huajiang control area, the ecological and social securities were raised, and the economic security was declined. In the Hongfenghu control area, the ecological security rose, the economic security did not change remarkably, and the social security declined a little. In the Yachi control area, the ecological security declined significantly, the economic security rose a little, and the social security declined slightly. (3) The sensitivities of ecological, economic and social securities to land use change are different obviously, and ecological security is the most sensitive among these securities. The results reveal that the effect of land use change on ecological security is most obvious. In the follow-up rocky desertification control and land use planning, we should focus on the effect of land use change on ecological security.
Remote sensing is an effective method to assess Light-use Efficiency (LUE) by using Photochemical Reflectance Index (PRI) at leaf level. But when extending this approach to canopy level, we found that the structure of forest canopy is one of the factors that influence the estimation accuracy of LUE. This study calculated the PRI, Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Modified Simple Ratio (MSR) respectively, using the spectral reflection data from the spectro-radiometer at the Dinghu Mountain Forest Ecosystem Research Station in Guangdong, southern China. We compared and analyzed the influence of different canopy structural vegetation indexes (NDVI, EVI and MSR) on PRI used to track LUE as measured by eddy covariance at the canopy level. A multivariate linear regression model was built to improve the fitting accuracy of LUE seasonal dynamics in this subtropical evergreen forest. The results show that: (1) Canopy structural vegetation index of subtropical evergreen forest has a significant correlation with PRI at canopy scale, and the correlation between MSR and PRI was the strongest (R2=0.40, P<0.01); (2) The estimation accuracy of LUE is better when high NDVI and MSR are observed because of larger canopy density and higher LAI; (3) Multivariate regression model between LUE and PRI constructed by NDVI, EVI and MSR improves the estimation accuracy of LUE by 18.14% in the observation period, and 54% from January to May. The LUE estimation method modified by the canopy structure can improve assessment of LUE in the light-use efficiency model, and the ability of remote sensing to accurately assess subtropical evergreen forest productivity.
To examine the spatiotemporal variation of vegetation in the lower reaches of the Tarim River, in this study, we use the cloud-free data of Landsat 5 TM and Landsat 8 OLI to obtain 22 time-series NDVI data during the period 1986-2017. We use the standard deviation of the NDVI time series to reflect vegetation change and the slope of linear regression equation of NDVI time series to reflect the variation tendency of vegetation. The results show that: (1) The distribution of vegetation is closely related to the distribution of water resources, mainly along the river channel and the water logged area. (2) For 1986-2000, the average NDVI value in the range within 1 km from the river channel fluctuated around 0.055, and showed a trend of slow decline because of the long-term absence of water supply. For 2000-2017, the average NDVI value showed an increasing trend and its fluctuation was closely related to volume and allocation of ecological water transportation. (3) The variance of NDVI time series in the study area was between 0.0077-0.1957, and there was obvious spatial difference. Its fluctuation was closely related to vegetation species. (4) The vegetation was in decline, which mainly occurred in the vicinity of Yingsu and old Yingsu during 1986-2000, but the vegetation mainly presented an increasing trend, and occurred mainly in the area along the river and east of Ka'erdayi during 2000-2017.
Rapid expansions of wells for irrigation water have led to severe groundwater depletion, posing serious challenge to future's food security in China. Finding solutions is critical for sustainable use of groundwater in China. As groundwater is a typical pool resource and its use gives rise to externalities, controlling well density could be a plausible solution. However, little empirical evidence is available in existing literature in China to analyze the relationship between well density and water tables. This paper therefore aims to fill in some of the gaps in existing literature using Lankao county in Henan province as a case study area. Based on household survey data and well census data, the paper conducts spatial analysis and econometric analysis to examine the relationship. It finds that there is a significant relationship between well density and groundwater tables. Specifically, for each increase in the number of surrounding wells within a radius of 100 m, the water table significantly decreases by 15 cm at a 5% significance level. Moreover, the marginal effect of well density on water table decreases significantly when the radius becomes larger and larger. Based on the findings, the paper emphasizes the importance of the government to control well density and develops a groundwater water permit system for sustainable management of groundwater in China.
Atmospheric precipitation is the most important link in the process of global water vapor cycle and energy conversion, and it is the material basis for the global ecosystem to maintain stability. Therefore, it is increasingly important to monitor and forecast precipitation for regional climate analysis, water resources evaluation and hydrological process simulation. As an important ecological barrier, the Qilian Mountains plays a critical role in maintaining the natural environment and social development in Northwest China. Thus, it is of great significance to examine the distribution and variation of precipitation in the Qilian Mountains. However, there are relatively few studies on precipitation in mountainous areas due to some factors, such as insufficient measured data, complicated precipitation environment and so on, which limits the further study to some extent. In recent years, with the development of satellite inversion technology, the application of satellite to precipitation retrieval is becoming more and more mature, which provides data support for the study of precipitation in mountainous areas. Therefore, this paper uses the data of TRMM monthly precipitation and ground meteorological station precipitation, combined with the error evaluation and other mathematical statistics and Kriging interpolation method, to calibrate TRMM precipitation, so as to examine the spatiotemporal variations of the zone of the maximum precipitation in the study area. The results show that: (1) The overall performance of TRMM precipitation is good in the Qilian Mountains. The measured annual precipitation of 31 meteorological stations has a high correlation (0.94) with the TRMM data, and the correlation coefficients of the seasonal average precipitation are 0.87 (spring), 0.89 (summer), 0.88 (autumn) and 0.7 (winter). (2) The errors of some stations are large and the low values are overestimated and the high values are underestimated. (3) Annual average precipitation shows a decreasing trend from east to west in the region, and zones of the maximum precipitation in the eastern, central and western parts appear at 4100 m, 4500 m and 4700 m, respectively. The vertical variation rates of the average annual precipitation are 16.6 mm/100 m, 10.8 mm/100 m, 9.8 mm/100 m, respectively. (4) The precipitation fluctuated and increased in the eastern, central and western parts of the study area from 1998 to 2016. The zone of the maximum precipitation also shows a fluctuating upward trend. The maximum precipitation height in each season decreases in the order of summer, spring, autumn and winter.
The grain production transformation is the core content of the evolution of the rural production system. The breakthrough of grain production transformation research can clearly reflect the evolution of regional rural man-land interactions, and provide a new perspective for deepening urban-rural integration and rural transformation. Based on the analysis of grain production transformation since China's reform and opening-up, this paper attempts to construct an analytical framework for China's grain production transformation. We identified four stages in transformation process of grain production, namely, grain as the key link, gricultural restructuring, comprehensive transformation and urban-rural integration. Using GL-RL model, the analytical framework of China's grain production transformation was constructed. It was found that the grain production evolved from "Green Loop" stage to "Red Loop" stage, which was gradually integrated from rural local production network into urban-rural production network. In addition, the disturbance factors driving the grain production transformation have multiple spatial-temporal features and cross-scale effects. Factors such as urban-rural integration development, rural vitalization strategy, rural man-land interactions, and globalization will have an important impact on future grain production transformation. Furthermore, optimizing the relationship between grain production and rural transformation provides guarantees for safeguarding the orderly transformation of grain production, and improving the conditions for creating the rural production system.
