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Spatial data partitioning (SDP) plays a powerful role in distributed storage and parallel computing for spatial data. However, due to skew distribution of spatial data and varying volume of spatial vector objects, it leads to a significant challenge to ensure both optimal performance of spatial operation and data balance in the cluster. To tackle this problem, we proposed a spatial coding-based approach for partitioning big spatial data in Hadoop. This approach, firstly, compressed the whole big spatial data based on spatial coding matrix to create a sensing information set (SIS), including spatial code, size, count and other information. SIS was then employed to build spatial partitioning matrix, which was used to spilt all spatial objects into different partitions in the cluster finally. Based on our approach, the neighbouring spatial objects can be partitioned into the same block. At the same time, it also can minimize the data skew in Hadoop distributed file system (HDFS). The presented approach with a case study in this paper is compared against random sampling based partitioning, with three measurement standards, namely, the spatial index quality, data skew in HDFS, and range query performance. The experimental results show that our method based on spatial coding technique can improve the query performance of big spatial data, as well as the data balance in HDFS. We implemented and deployed this approach in Hadoop, and it is also able to support efficiently any other distributed big spatial data systems.

The scientific and reasonable division of geographical units of cultivated land reserve resource areas is an important foundation for comprehensive land consolidation (CLC). Saline–alkali land is an important cultivated land reserve resource, and is significant for ensuring food security. This paper constructs a two-level land consolidation index system for cultivated land reserve resource areas. The Kruskal graph theory clustering algorithm was used to divide the study area into four types of ecological zones. On the basis of ecological zones, the study area was further divided into three types of consolidation units. Finally, the spatial relationship between ecological zoning and land use types was clarified, and the classification distribution of land consolidation potential was determined through an analysis of the CLC of two-level geographical units. Da'an City, Jilin province, China, was selected as the study area. The results of this study show the following: (1) In Da'an City, the conservation priority areas are concentrated in the north, the development priority areas are concentrated in the central and southern areas, and the comprehensive upgrade areas and adjustment rebuilding areas are in the transition zones. (2) The CLC potential trend is low in the north but high in the south in Da'an City. This paper proposes a framework for a geographical unit delineation method for saline–alkali-enriched cultivated land reserve resource zones, and analyzes the spatial layout of ecological protection demands and land consolidation potential in Da'an City. The results and conclusions of this study will provide a reference for CLC in cultivated land reserve resource areas. [ABSTRACT FROM AUTHOR]

Extreme drought is increasing in frequency and intensity in many regions globally. Understanding the changes in vegetation resistance and resilience under aggravated drought is essential for maintaining regional ecosystem stability. In this study, a drought event–vegetation response framework was developed to explore vegetation resistance and resilience changes. The normalized difference vegetation index (NDVI) was correlated with the standardized precipitation evapotranspiration index (SPEI) at multiple timescales to screen out the vegetation response time to drought. Then, the SPEI for the response time was detected using run theory to identify drought events during the period 2000–2017. Finally, drought-induced NDVI anomaly changes were identified using a sliding window to explore the changes in resistance and resilience to drought. This study focuses on Jilin province, China, which contains a famous environmentally vulnerable area. The results illustrate that the response time of vegetation to drought is 3 months. The northwest of Jilin province is considered to be drought-vulnerable because it has suffered the most drought events, i.e., 19–21 times, with severities in the range of 2.6–3.2 and durations in the range of 3.6–4.1 months. Grassland shows the weakest resistance and the strongest resilience, and tree cover shows the strongest resistance and the weakest resilience under severe drought disturbance among all vegetation. As the severity and duration of drought increase, the resistance decreases, and the resilience increases. During the growing season, the drought from May to July significantly impacts the vegetation resistance. Drought occurring from June to July has much less impact on resilience. Drought in August to September has less impact on resistance and a more significant impact on resilience. The results of this study may increase our knowledge regarding the response of vegetation to drought and guide ecosystem stability restoration. [ABSTRACT FROM AUTHOR]

Reserved resource for cultivated land is an important supplement to cultivated land, and it plays an important role in requisition-compensation balance, however, it has disadvantages of subjectiveness and emphasizing on quantity in cultivated land supplement. It is necessary to play the role of farmland reserve resources to replenish cultivated land for the realization of the goal of farmland protection in the overall planning period of county land use. Data used for study are from the results of the new round of 'survey and evaluation of reserved resource for cultivated land'. A balancing method, which focused on both quantity and quality and was based on the ratio of added cultivated land and grade conversion coefficient, were proposed to analyze the capability of requisition-compensation balance in the planning period. And we analyzed the capacity to achieve the balance of arable land in the county planning period. The coefficient of newly increased cultivated land was developed by the weighted average of the newly cultivated land rate. The conversion coefficient of requisition and compensation of arable land is based on the national unified research results of arable land's requisition compensation balance according to grade conversion coefficient from Land Resources and Land Rehabilitation Center. Taking Yuanjiang City, Hunan Province as an example, we calculated the area of reserved resource for cultivated land needed for realizing both quantitative and qualitative balance. According to the "Yuanjiang City land use overall planning (during 2006-2020)", the new construction area of farmland was expected to not more than 899.2 hm2 until 2020, the quality of new construction occupation of cultivated land focused on the level of 1-5, whose composition ratios were 40.61%, 16.15%, 22.73%, 18.8% and 1.72%, respectively. The reserved resource area of cultivated land in Yuanjiang City was 1 744.14 hm2, of which 1 447.64 hm2 cultivated land can be added after the correction of the coefficient of newly cultivated land. Results showed that 1083.37 hm2 of reserved resource for cultivated land should be developed to meet the requirement of quantity balance of cultivated land. When the quality of cultivated land was at the level of 1-5, the minimum development area was 1 083.37 hm2, and the highest was 1 473.39 hm2, while according to the composition of quality grade of cultivated land, at least 1 083.37 hm2 of reserved resource for cultivated land should be developed to meet the requirement of quantity-quality balance, and 1 351.65 hm2 for the maximum. According to the area of the remaining arable land reserved, cultivated land development can last at most for 5 a, and at least for 2 a. Through analyzing, we find that the total area of reserved cultivated land in Yuanjiang city can meet the requirement of requisition-compensation balance which focuses on both quantity and quality. But there is a big pressure on requisition-compensation balance, especially on the quantity-quality balance. Therefore, to know the capability of requisition-compensation balance is in favor of planning construction project reasonably and reaching the goal of cultivated land protection targeted in the overall plan of land utilization. [ABSTRACT FROM AUTHOR]

The enhancement of cultivated land quality is an important measure to improve the production capability and ensure the food safety. At the construction course of cultivated land quality informatization, novel methods and techniques are promising to improve the current working pattern as well as raise the efficiency of cultivated land quality management. Irrigation guarantee capability is an important element of cultivated land quality monitoring, evaluation and construction. Evapotranspiration (ET) derived from remote sensing can be used for rapid monitoring of irrigation guarantee capability of cultivated land at the regional scale. In order to improve the acquisition efficiency of the regional cultivated land quality monitoring, a new evaluation method was proposed for irrigation capability evaluation of cultivated land based on Moderate Resolution Imaging Spectroradiometer (MODIS) ET products. First, in order to reduce the representative errors of meteorological data, the relationship between the monthly potential evapotranspiration (PET) parameter derived from MODIS evaporation products and the reference crop evapotranspiration (ET0) calculated from observed meteorological data with the Penman-Monteith (P-M) formula was analyzed. The continuous ET0 in space was obtained from the regression model. And then, water requirements for crop were obtained by the map of crop type from the classification of Landsat TM data and space-continuous ET0. Furthermore, the annual water requirement was calculated according to the difference of the water requirement for crop and the rainfall which was effectively consumed by crop. Additionally, based on the regional water balance principle, the actual quantity of irrigation was obtained from the difference of actual evaporation derived from ET products of MODIS and effective rainfall. The evaluation index of irrigation guarantee capability is defined as the ratio of the annual irrigation requirement and the actual quantity of irrigation, and used for the monitoring and evaluation of cultivated land irrigation guarantee capability. Finally, application and analysis were conducted in Hengshui City, Hebei Province, China. The R2 of the regression model between the PET and ET0 from meteorological stations reached 0.89. And the calculated results of the evaluation index of irrigation guarantee capability from 2005 to 2012 accurately reflected temporal-spatial variations for the cultivated land irrigation capability. Meanwhile, the comprehensive evaluation of irrigation capability, which was from the supervised classification results based on actual survey, had a good agreement with the classification results of irrigation probability in the gradation on agriculture land quality which had been updated in 2012. The area with no grade difference was up to 37% of the total cells, 38% of the study area had one-grade difference, and the area with two-grade difference was 19% of the study area. The area with three-grade difference only accounted for 6%. The grade difference of more than 75% of the cultivated land was less than one grade. Errors were mainly concentrated in the cultivated land around the city, because the MOD16A2 product with 1-km resolution was inadequate to accurately represent the information of that complex planting structure of cultivated land, and this problem would be solved with the development and improvement of remote sensing earth observation systems with higher resolution. The evaluation index of irrigation capability proposed in this paper has the advantage of clear physical meaning and easy data accessing. The experiment results indicate that the method can meet the needs of the regional cultivated land quality monitoring and evaluation. [ABSTRACT FROM AUTHOR]

The results of cultivated land quality gradation are made of the results of county, provincial, national levels. The results at the provincial level are integrated by the results at the county level. Provincial integration is an essential link in cultivated land quality grading work. The traditional provincial integration methods excessively depend on the provincial integration base map, which makes the integration efficiency low. Moreover, the quality of integration work completely depends on the quality of integration base map. Based on these defects, this paper comes up with a method that uses the grid instead of the integration base map. In provincial integration work, we need to build traceability relation between county units and provincial units. It requires all county units can find provincial units and all provincial units have their corresponding county units. Moreover, there is a principle we have to abide by: the ownership, the land type and the grade should be coincident between the county units and corresponding provincial units. That is "ownership-land type-grade" coincident principle. The purpose of this method is to make spatial distribution of provincial cultivated land quality is similar to that of the county when abiding by this principle. First we need to classify the county results according to "ownership-land type-grade". Then we determine the corresponding grid category according to the area dominant principle. Through the spatial nearest neighboring method, we find the grid unit closest to the unit at the county level to build "Grid-County grading unit" relations. But maybe there are some categories which can't be found in the provincial grids. Based this situation, the barycenter of the missing category was firstly calculated, then an uncultivated area grid closest to the barycenter was searched out, and lastly this grid was marked as the missing category. The grid coding method proposed in this paper stipulates that grid code is formed by county's administrative code, the grid rank, quality gradation and land class code. The length of the code is 21. At last, this paper uses the mean center and standard deviational ellipse to test the similarity of the spatial distribution of cultivated land before and after integration. This paper takes Daxing district, Bejing as a study area. By "ownership-land type-grade", there are 8 categories in Daxing. According to the distribution of cultivated land in Daxing district, 688 valid cultivated land grids were finally determined. Using the method in this article, we completed the integration at the provincial level for Daxing. After test, it showed that the difference of mean center between provincial grid results and county results is only 405.6 m, and the difference of distribution direction is only 0.34°, which means that this method can ensure the consistency of spatial distribution of cultivated land at different levels. Compared with the method which depends on the integration base map, the method based on grid doesn't make base map, reduces workload and improves work efficiency. This method orientates the provincial cultivated land into each grid and codes for these grids. Through grid code, we can quickly search cultivated land quality in the corresponding position, which is very convenient for both management and application. [ABSTRACT FROM AUTHOR]

As the material basis for the development of modern agriculture, well-facilitated capital farmland is the key to ensuring food safety in China By improving the comprehensive productivity of cultivated land and agricultural production conditions, the construction of well-facilitated capital farmland and its effective management and efficient utilization has great significance for food security and the development of modern agriculture. Taking Fujin city of Heilongjiang Province as an example, the paper conducted a study on the well-facilitated capital farmland construction sequence. The main conclusions of the study were as follows: It introduces the Four Quadrant model by a feasibility and spatial stability analysis on a well-facilitated capital farmland construction sequence. It comprehensively determined a well-facilitated capital farmland construction sequence combined with the construction scale and goal orientation. Evaluation of the construction feasibility is mainly used to reflect the feasibility of a well-facilitated capital farmland construction sequence. The evaluation index was selected from three aspects including natural quality, engineering construction, and economic society. It mainly included thickness of effective soil, field area, and the later maintenance funding levels. Spatial stability evaluation is mainly used to reflect the spatial stability after well-facilitated capital farmland is constructed. It selected the distance to the county seat, the distance to the township, the distance to the main roads, the distance to potential geological hazards, population density, local finance income, and other indicators from three aspects including location, ecology, and the construction land expansion force. The cultivated land to be evaluated was divided into three levels including high feasibility, medium feasibility, and low-grade feasibility based on the well-facilitated capital farmland construction feasibility evaluation model. The area of the highly feasible region was 13.18×104hm2 (22.69% of the total evaluation area), it was mainly in the state farms especially in the Qixing Farm and the Daxing Farm. The moderate feasible area was 22.72×104 hm2 (39.13% of the total evaluation area). It was distributed in the state farm and local government areas and the area was equal. It was mainly distributed in the Daxing Farm and the Qixing Farm of the state farms and Jinshan town of the local government; The low feasible area was 22.18×104hm2 (38.18% of the total evaluation area), all are located in the local government's area except for a little distribution in Qianjin Farm. On the issue of space stability, the area of highly stability, area of moderate stability, and area of low stability of well-facilitated capital farmland construction in Fujin City was 7.58×104hm2, 27.73×104hm2 and 22.77×104 hm2. It occupied respectively 13.06%, 47.73%, and 39.21% of the evaluation area. Highly stable areas were mainly distributed in the farm on the east of Fujin city; moderate stability areas were mainly distributed in the local towns in the south and west of Fujin city; and low stability areas were mainly distributed in the township in the western northern and central areas of Fujin city. The unstable areas were mainly distributed in the Songhua River, Sanhuanpao Nature Reserve, and some important areas of the rivers and city construction expansion area. It was coupled to the feasibility and spatial stability of well-facilitated capital farmland construction by the Four Quadrant model. It determined the well-facilitated capital farmland construction sequence based on the goal orientation of spatial stability priority. Qixing Farm, Hongwei Farm, Qianjin Farm, and Qinglongshan Farm are priority areas of well-facilitated capital farmland construction. [ABSTRACT FROM AUTHOR]