中国南方调整水稻种植格局——一种水稻生产预先适应气候变化的选择(英文)

Rice planted in southern China accounts for 94% of the total in sown acreage and 88% of the total in production, which matters a lot to Chinese food security. However, due to the prolonged conflict between water availability and rice growth in spatial/temporal distribu-tion, rice production suffers from seasonal drought at acreage of 16%-22%, which compro-mises food production capacity and food security. Focusing on the spatial distribution of seasonal drought with rice and the practices to adapt to it, and based on an analysis of bal-anced water supply for and demand by rice at a growing season scale during 1981-2030, this paper assesses the changing seasonal drought in the process of rice production under the changing climate in the future, and identifies general rice re-cultivation options for climate change adaptation. Some conclusions can be drawn as follows. (1) Rice suggests a decline in seasonal drought, with early season rice (early rice hereafter) by 12,500 km2, middle season rice (middle rice) by 80,000 km2, and in particular late season rice (late rice) by 25,000 km2, which accounts for almost 20% of its cultivated acreage. It is indicated that due to climate change, seasonal drought in major rice producing areas tends to alleviate in general, late season rice in particular. (2) Future climate change brings about a significant impact on the spatial/temporal distribution of water resources in rice producing areas in China. Based on ’pre-designed’ adaptation actions for rice-re-cultivation, the rice cultivation pattern undergoes a significant alteration between 1981-2000 and 2001-2030. In eastern Guizhou and western Hunan, the pattern of single early plus single dry farming is changed into double cropping. In eastern Hunan, the pattern of dry cropping is changed into single early plus single dry farming. In northern Anhui, the pattern of dry farming cropping is changed into middle rice. All this is aimed at a potential adequate availability of water for rice production in the future. (3) Rice re-cultivation patterns developed in this paper help re-balance water demand and supply for rice growth using the spatial analysis tool to adapt rice growth to the changing water avail-ability from spatial perspective, and come up with rice producer-friendly re-cultivation options in response to climate change.     

鄱阳湖区2004-2010年水稻种植制度时空变化(英文)

Rice cropping systems not only characterize comprehensive utilization intensity of agricultural resources but also serve as the basis to enhance the provision services of agro-ecosystems.Yet,it is always affected by external factors,like agricultural policies.Since 2004,seven consecutive No.1 Central Documents issued by the Central Government have focused on agricultural development in China.So far,few studies have investigated the ef-fects of these policies on the rice cropping systems.In this study,based upon the long-term field survey information on paddy rice fields,we proposed a method to discriminate the rice cropping systems with Landsat data and quantified the spatial variations of rice cropping systems in the Poyang Lake Region(PLR),China.The results revealed that:(1) from 2004 to 2010,the decrement of paddy rice field was 46.76 km2 due to the land use change.(2) The temporal dynamics of NDVI derived from Landsat historical images could well characterize the temporal development of paddy rice fields.NDVI curves of single cropping rice fields showed one peak,while NDVI curves of double cropping rice fields displayed two peaks an-nually.NDVI of fallow field fluctuated between 0.15 and 0.40.NDVI of the flooded field during the transplanting period was relatively low,about 0.20±0.05,while NDVI during the period of panicle initiation to heading reached the highest level(above 0.80).Then,several temporal windows were determined based upon the NDVI variations of different rice cropping systems.(3) With the spatial pattern of paddy rice field and the NDVI threshold within optimum tem-poral windows,the spatial variation of rice cropping systems was very obvious,with an in-creased multiple cropping index of rice about 20.2% from 2004 to 2010.The result indicates that agricultural policies have greatly enhanced the food provision services in the PLR,China.     

中国省域耕地集约利用态势与驱动力分析(英文)

The aim of this study is to establish several important factors representing land use intensification in cultivated land(denoted by CII), using a multi-dimensional approach to achieve realistic and practical cultivated land use policies in China. For this reason, the theoretical framework was first built to explain the changes of land use intensification in the cultivated land, and then the variables and index were further developed for the purpose of characterizing the dynamic trends and driving forces of the land use intensification in the cultivated land at the provincial level. The study results indicate that the extent of CII significantly increased during the period of 1996 to 2008, due to the extensive use of fertilizers, machinery and pesticide, increased labor and capital input, and intensified land use. Moreover, the principal component regression results show that the productivity of cultivated land, economic benefits of cultivated land, labor productivity, and land use conversion are the main factors affecting the village development. The first three factors play a positive role, while the last one has a negative effect on the land use intensification in the cultivated land. According to these results, the main policies for sustainable intensification in cultivated land are proposed. First, the sustainable pathways for intensification should be adopted to reduce the unsustainable uses of chemical fertilizer, agricultural chemicals, etc. Second, the conditions for agricultural production should be further improved to increase the cultivated land productivity. Third, it is very necessary and helpful for improving labor productivity and land use efficiency from the viewpoint of accelerated the cultivated land circulation. The last step is to positively affect the production activities of peasants by means of reforming the subsidy standards.     

利用GIS和Dyna-CLUE模拟泰国东北部粮食作物保护区土地利用变化（英文）

Land use in the northeast region of Thailand has changed dramatically in the past two decades. These changes are mainly due to the government policies, which launched a scheme to promote rubber plantation during 2003–2013 targeting to solve the problem of poverty in the region. At least 50,000 ha of paddy fields were found to be converted to other land use types between 2002 and 2012. This study was conducted in Nong Khai and Bueng Kan province of northeast Thailand, where massive rubber plantation is going on prompting significant amount of land-use change, with the objective of investigating how land-use changes will affect on food availability in future. We analyzed land-use changes of the past and simulated future land uses using GIS and Landsat Thematic Mapper Data. The most obvious change was the decrease in paddy field and an increase in rubber plantation. This eventually leads to decreased paddy production affecting food supply of farm households. The land use projections for 2032 were done for three scenarios using Dyna-CLUE model. Unlike business as usual scenario, which will further decrease the paddy area, other scenarios with different land use policies if implemented will help protect paddy areas and thus achieving higher food production locally. The lack of implementation of proper spatial policies will lead to a further loss of paddy areas at macro level.The smallholder farmers may be highly vulnerable to land use-change and experience significant food crop losses, food insecurity and income loss when they change the land to rubber and there is market failure.     

The spatial—temporal dynamic characteristics of the marsh in the Sanjianlg Plain

Using the methods of combining landscape ecology with GIS spatial analysis,this paper analyses the dynamics of the marsh landscape stucture of the Sanjing Plain in the past 20 years,furthermore,taking Fujin County,located in the north of the plain,as an example,analyzes the conversion between marsh and other land use types.It is shown that the marsh in the Sanjiang Plain decreased greatly in the past 20 years,but the trend has begun to reverse,The marsh area decreased by 51.33% from 1980 to 1996,whereas it decreased by 4.19% from 1996 to 2000.The fragmentation of the marsh increased;the number of the patches increased by 326 from 1986 to 1996,whereas it only increased by 18 patches from 1996 to 2000,It is obvious that the speed of patches number diminished and the marsh fragmentation decreased,which shows that the reclamation of the marsh converted from the fragmentation to the brim in a large area of the marsh.The reclaimed marsh has mainly converted to paddy field and dry land .Large area of the marsh.The reclaimed marsh has mainly converted to paddy fiedld and dry land.Large-scale reclamation in the Sanjiang Plain influences its natural environment directly:the climate of the region turns from cold and wet to warm and dry,which makes the marsh both in the low-temperature northern part and in the deeply stagnant eastern part suitable for further agricultural development.     

华北地下水超采区冬小麦退耕的生态补偿（英文）

The land fallow policy was adopted by central and local governments to encourage the abandonment of water-intensive crops, such as winter wheat, in groundwater over-exploited areas. At the same time, since the 1990 s, many households in the North China Plain(NCP) have chosen to replace the winter wheat and summer maize double-cropping system with the spring maize single-cropping system. Therefore, it is crucial to identify target land parcels for winter wheat abandonment and to design reasonable and proper standards for ecological compensation prior to the implementation of the land fallow policy in the NCP. In this study, multi-level logit models were used with household survey data in order to detect determinants across land parcel, household and village levels on household cropping system decisions; the opportunity costs for winter wheat abandonment were also calculated using cost–benefit analysis. The results show that:(1) land quality and irrigation condition at parcel level are two essential elements influencing household cropping system decisions. Nearly 70% of the total area of poor land and more than 90% of the total area of unirrigated land has suffered winter wheat abandonment. Target land parcels for the land fallow policy should be those that are irrigated and of high quality.(2) There were no significant differences between net profits from spring maize and summer maize under similar farming conditions, and the opportunity cost for winter wheat abandonment should be equal to the net profit of winter wheat.(3) The primary purpose of the land fallow policy is to induce groundwater recovery and restoration as a preliminary stage. A higher level of 350 yuan/mu is recommended as subsidy for ecological compensation at this stage. Later, the primary purpose of the policy should be a transition to a balance between exploitation and supplementation of water resources, and a lower level of 280 yuan/mu is recommended as a subsidy at this stage.     

“一带一路”沿线区域耕地格局变化（英文）

The Belt and Road Initiative(BRI)–a development strategy proposed by China – provides unprecedented opportunities for multi-dimensional communication and cooperation across Asia,Africa and Europe.In this study,we analyse the spatio-temporal changes in cultivated land in the BRI countries(64 in total) to better understand the land use status of China along with its periphery for targeting specific collaboration.We apply FAO statistics and Globe Land30(the world's finest land cover data at a 30-m resolution),and develop three indicator groups(namely quantity,conversion,and utilization degree) for the analysis.The results show that cultivated land area in the BRI region increased 3.73×10~4 km~2 between 2000 and 2010.The increased cultivated land was mainly found in Central and Eastern Europe and Southeast Asia,while the decreased cultivated land was mostly concentrated in China.Russia ranks first with an increase of 1.59×10~4 km~2 cultivated land area,followed by Hungary(0.66×10~4 km~2) and India(0.57×10~4 km`2).China decreased 1.95×10~4 km~2 cultivated land area,followed by Bangladesh(–0.22×10~4 km~2) and Thailand(–0.22×10~4 km~2).Cultivated land was mainly transferred to/from forest,grassland,artificial surfaces and bare land,and transfer types in different regions have different characteristics:while large amount of cultivated land in China was converted to artificial surfaces,considerable forest was converted to cultivated land in Southeast Asia.The increase of multi-cropping index dominated the region except the Central and Eastern Europe,while the increase of fragmentation index was prevailing in the region except for a few South Asian countries.Our results indicate that the negative consequence of cultivated land loss in China might be underestimated by the domestic-focused studies,as none of its close neighbours experienced such obvious cultivated land losses.Nevertheless,the increased cultivated land area in Southeast Asia and the extensive cultivated land use in Ukraine and Russia imply that the regional food production would be greatly improved if China' "Go Out policy" would help those countries to intensify their cultivated land use.     

1999-2007年中国耕地利用变化——政策演进视角(英文)

Cultivated land protection (CLP) entered the new era of macro administration in 1999 in China. This paper presents a holistic analysis of cultivated land use change concerning the three goals of the CLP, i.e., grain security, ecological security and harmonizing regional development. Farmers’ willingness to grow grain has been the key factor in safeguarding grain security. Grain-for-green policy has contributed to improving ecological state especially in the western provinces. Effects of the land macro-control of the CLP on harmonizing regional development were significant. Moreover, cultivated land use change in 1999-2007 points out the way of the evolving policy in the future. From the viewpoint of normative concept of multifunctionality, we discuss development of the three land functions, i.e., production function, environmental function and carrier function. Finally, we propose to emphasize multifunctional land management based on regional differences to promote transition of the CLP.     

2000–2012年中国黄淮海农业区多熟种植时空变化（英文）

Multiple cropping index(MCI) is the ratio of total sown area and cropland area in a region,which represents the regional time intensity of planting crops.Multiple cropping systems have effectively improved the utilization efficiency and production of cropland by increasing cropping frequency in one year.Meanwhile,it has also significantly altered biogeochemical cycles.Therefore,exploring the spatio-temporal dynamics of multiple cropping intensity is of great significance for ensuring food and ecological security.In this study,MCI of Huang-Huai-Hai agricultural region with intensive cropping practices was extracted based on a cropping intensity mapping algorithm using MODIS Enhanced Vegetation Index(EVI) time series at 500-m spatial resolution and 8-day time intervals.Then the physical characteristics and landscape pattern of MCI trends were analyzed from 2000–2012.Results showed that MCI in Huang-Huai-Hai agricultural region has increased from 152% to 156% in the 12 years.Topography is a primary factor in determining the spatial pattern dynamics of MCI,which is more stable in hilly area than in plain area.An increase from 158% to 164% of MCI occurred in plain area while there was almost no change in hilly area with single cropping.The most active region of MCI change was the intersection zone between the hilly area and plain area.In spatial patterns,landscape of multiple cropping systems tended to be homogenized reflected by a reduction in the degree of fragmentation and an increase in the degree of concentration of cropland with the same cropping system.     

1980–2011年中国农作物种植结构时空变化（英文）

Understanding the spatial and temporal variations of cropping systems is very important for agricultural policymaking and food security assessment,and can provide a basis for national policies regarding cropping systems adjustment and agricultural adaptation to climate change.With rapid development of society and the economy,China's cropping structure has profoundly changed since the reform and opening up in 1978,but there has been no systematic investigation of the pattern,process and characteristics of these changes.In view of this,a crop area database for China was acquired and compiled at the county level for the period 1980–2011,and linear regression and spatial analysis were employed to investigate the cropping structure type and cropping proportion changes at the national level.This research had three main findings:(1) China's cropping structure has undergone significant changes since 2002;the richness of cropping structure types has increased significantly and a diversified-type structure has gradually replaced the single types.The single-crop types—dominated by rice,wheat or maize—declined,affected by the combination of these three major food crops in mixed plantings and conversion of some of their planting area to other crops.(2) In the top 10 types,82.7% of the county-level cropping structure was rice,wheat,maize and their combinations in 1980;however,this proportion decreased to 50.7% in 2011,indicating an adjustment period of China's cropping structure.Spatial analysis showed that 63.8% of China's counties adjusted their cropping structure,with the general change toward reducing the main food types and increasing fruits and vegetables during 1980–2011.(3) At the national level,the grain-planting pattern dominated by rice shifted to coexistence of rice,wheat and maize during this period.There were significant decreasing trends for 47% of rice,61% of wheat and 29.6% of maize cropping counties.The pattern of maize cropping had the most significant change,with the maize proportion decreasing in the zone from northeastern to southwestern China during this period.Cities and their surroundings were hotspots for cropping structural adjustment.Urbanization has significantly changed cropping structure,with most of these regions showing rapid increases in the proportion of fruit and vegetables.Our research suggests that the policy of cropping structural adjustment needs to consider geographical characteristics and spatial planning of cropping systems.In this way,the future direction of cropping structural adjustment will be appropriate and scientifically based,such as where there is a need to maintain or increase rice and wheat cropping,increase soybean and decrease maize,and increase the supply of fruit and vegetables.     

北京城市空间发展和土地利用—伦敦经验启示

Beijing is facing a huge challenge to manage the growth of its built-up area whilst also retaining both productive arable land and land for conservation purposes in order to simultaneously realize the three aims of economic development,protecting arable land and generating environmental improvements. Meanwhile,London,as a world city with more than 200 years of industrialization and urbanization,has accumulated rich theoretical and practical experiences for land use planning in a major urban area,such as the creation of Garden Cities,a designated Green Belt and New Towns. This paper firstly analyzes the main characteristics of the spatial distribution of the built-up area,arable land and conservation land in Beijing. Then,some of the key aspects of urban fringe planning in the London region are examined. Lastly,several implications from the experience of London are provided with respect to land-use planning for Beijing,concentrating on a re-appraisal of land-use functions around Beijing,measures to improve the green belt,the development of small towns to house rural-urban migrants and urban overspill,and effective implementation of land-use planning.     

三峡库区秭归县和兴山县的土地利用

In this study the arable land changes in two counties (Zigui and Xingshan) in the Three Gorges Reservoir area in China are investigated. The statistical data fTom the officially published statistical books are used to study these changes in the two counties during the past 50 years since 1949. The changes of arable land, changes of arable land per capita, and changes of multiple crop index in Zigui and Xingshan counties are examined. Using an index method, we conclude that the two counties are critical in the sustainable utilization of arable land.     

Change analysis of rice area and production in China during the past three decades

Rice＇s spatial-temporal distributions, which are critical for agricultural, environ- mental and food security research, are affected by natural conditions as well as socio-eco- nomic developments. Based on multi-source data, an effective model named the Spatial Production Allocation Model （SPAM） which integrates arable land distribution, administrative unit statistics of crop data, agricultural irrigation data and crop suitability data, was used to get a series of spatial distributions of rice area and production with 10-km pixels at a national scale -it was applied from the early 1980s onwards and used to analyze the pattern of spatial and temporal changes. The results show that significant changes occurred in rice in China during 1980-2010. Overall, more than 50% of the rice area decreased, while nearly 70% of rice production increased in the change region during 1980-2010. Spatially, most of the increased area and production were in Northeast China, especially, in Jilin and Heilongjiang; most of the decreased area and production were located in Southeast China, especially, in regions of rapidly urbanization in Guangdong, Fujian and Zhejiang. Thus, the centroid of rice area was moved northeast approximately 230 km since 1980, and rice production about 320 km, which means rice production moved northeastward faster than rice area because of the significant rice yield increase in Northeast China. The results also show that rice area change had a decisive impact on rice production change. About 54.5% of the increase in rice pro- duction is due to the expansion of sown area, while around 83.2% of the decrease in rice production is due to contraction of rice area. This implies that rice production increase may be due to area expansion and other non-area factors, but reduced rice production could largely be attributed to rice area decrease.     

Coordinated development efficiency between cultivated land spatial morphology and agricultural economy in underdeveloped areas in China: Evidence from western Hubei province

Suitable spatial morphology of cultivated land is a basic requirement for sustaining agricultural economic development in mountainous areas. Coordinated development efficiency of cultivated land spatial morphology and agricultural economy(CECA) is of great practical significance to measure the efficiency of cultivated land use, and thereby promote regional rural revitalization. However, few studies to date have focused on coordinated development efficiency between cultivated land use and agricul...     

20世纪80年代以来全球耕地变化的基本特征及空间格局（英文）

In this paper, we analyzed the spatial patterns of cultivated land change between 1982 and 2011 using global vector-based land use/land cover data.(1) Our analysis showed that the total global cultivated land area increased by 528.768×104 km~2 with a rate of 7.920×104 km~2/a, although this increasing trend was not significant. The global cultivated land increased fastest in the 1980 s. Since the 1980 s, the cultivated land area in North America, South America and Oceania increased by 170.854×104 km~2, 107.890×104 km~2, and 186.492×104 km~2, respectively. In contrast, that in Asia, Europe and Africa decreased by 23.769×104 km~2, 4.035×104 km~2 and 86.76×104 km~2, respectively. Furthermore, the cultivated land area in North America, South America and Oceania exhibited significant increasing trends of 7.236× 104 km~2/a, 2.780×104 km~2/a and 3.758×104 km~2/a, respectively. On the other hand, that of Asia, Europe and Africa exhibited decreasing trend rates of –5.641×104 km~2/a, –0.831×104 km~2/a and –0.595×104 km~2/a, respectively. Moreover, the decreasing trend in Asia was significant.(2) Since the 1980 s, the increase in global cultivated lands was mainly due to converted grasslands and woodlands, which accounted for 53.536% and 26.148% of the total increase, respectively. The increase was found in southern and central Africa, eastern and northern Australia, southeastern South America, central US and Alaska, central Canada, western Russia, northern Finland and northern Mongolia. Among them, Botswana in southern Africa experienced an 80%–90% increase, making it the country with the highest increase worldwide.(3) Since the 1980 s, the total area of cultivated lands converted to other types of land was 1071.946×104 km~2. The reduction was mainly converted to grasslands and woodlands, which accounted for 57.482% and 36.000%, respectively. The reduction occurred mainly in southern Sudan in central Africa, southern and central US, southern Russia, and southern European countries including Bulgaria, Romania, Serbia and Hungary. The greatest reduction occurred in southern Africa with a 60% reduction.(4) The cultivated lands in all the continents analyzed exhibited a trend of expansion to high latitudes. Additionally, most countries displayed an expansion of newly increased cultivated lands and the reduction of the original cultivated lands.     

贫困地区荒山土地整治的综合效应研究——以河北省阜平县为例（英文）

Land is the root of rural revitalization, and its core is to reinvigorate land resources through the building up of land capacity. Since the late 1990s, land consolidation efforts have been widely extended to all parts of China. Land consolidation has served as an essential instrument for reinvigorating stock land, strengthening intensive land use, timely supplementing cultivated land, and promoting agricultural modernization, as well as urban-rural integration. This study uses a typical poor village(Dadao Village) in a state-designated impoverished county(Fuping County, Hebei Province), to analyze the socioeconomic benefits and eco-environmental impacts of land consolidation. With the aid of first-hand data from questionnaire surveys, face-to-face interviews and the visual interpretation of land use and land cover changes(LUCC), we found that: 1) the barren hilly land consolidation(BHLC)helps to promote the transformation of resource-advantages into asset-advantages in poverty-stricken areas. In 2017, 60.16% households in the study area gained the additional transferred-income with an annual average of 2843 yuan, while 19.11% households received the wage-income with an annual average of 9871 yuan. 2) Land consolidation inspires farmers' enthusiasm to participate in village government and helps alleviate rural poverty. From 2014 to 2017, land consolidation has helped 585 poor in the village out of poverty. Meanwhile,by land consolidation, most farmers' attitudes towards land consolidation have shifted from"not caring" to "have great concern," and their identity cognition has gradually changed from being bystanders to becoming decision makers and supervisors. 3) Further analysis demonstrated that land consolidation could not only increase the quantity and quality of arable land,but also have a certain impact on eco-environment. During 2014–2016, the BHLC in the study area transformed 242.12 ha unused barren hilly land and open forest land into well-facilitated arable land, and increased the average arable land by 0.19 ha per capita. Also, the index of land use intensity increased by 27.01% between 2014 and 2016. Farmers' perceptions of environmental awareness have confirmed that such high-intensity LUCC were significant enough to make two-side impacts on eco-environment. We appeal to establish a combined organization and encouragement mechanism of rural land consolidation, to take the full breadth and depth of farmers' participation into consideration, and to formulate more scientific and sustainable land consolidation planning. Also, we put forward some suggestions and notes for the implementation and promotion of BHLC model. These findings can provide beneficial references for those involved in policymaking and planning in the areas of land consolidation and poverty alleviation in China, as well as other developing countries around the world.     

Feasibility analysis of a double-cropping system for the efficient use of farmland on China's Loess Plateau

Cropping systems worldwide have been affected by the current trend in global warming and the optimization of cropping systems is an important area of research in the transition of agricultural land. The Loess Plateau is a typical ecologically fragile region with the most serious soil erosion in China. We carried out a field experiment in Yan’an city on the Loess Plateau to explore the effect of sowing date on crop growth and yield. We then analyzed the feasibility of a double-cropping system by ...     

Extent and spatial distribution of terrace abandonment in China

Driven by urbanization and industrialization, arable land in hilly and mountainous regions of China is gradually becoming marginalized, with the extent of arable land abandonment rapidly expanding from poor-quality sloping arable land to high-quality terraces. The abandonment of large-scale terraces will lead to a series of socio-economic and ecological effects. A national sample survey was used to investigate the extent and spatial distribution of terrace abandonment in China, and a total of 56...     

中全新世黄河流域耕地格局重建及对原生植被的影响(英文)

Yangshao culture is the most important mid-Holocene Neolithic culture in the Yellow River catchment,and thus,a study on the impact of human activities on the environment is important.In the current study,the distribution pattern of the cultivated land in late Yangshao culture is reconstructed using GIS tool and site domain analysis(SDA).The results show that the cultivated land during 5.5-5.0 ka BP was mainly distributed in the Weihe River valley,Luohe River valley,northwestern Henan Plain,Fenhe River valley and eastern Gansu region,especially concentrated in the Xi’an-Baoji line of the Weihe River valley.At that time,at least 37,000 km 2 of lands were reclaimed in the middle and lower reaches of the Yellow River,and 132,000 km 2 of lands were affected by agricultural activities.Human activities had become the driving force of land use/land coverage.Charcoal records indicate that the ancestors of Yangshao culture burnt forests for reclamation,leading to the decrease of arbor pollen at 5 ka BP in core areas of the Yangshao culture.The areas that were significantly affected by human activities accounted for 3.2% of the Yangshao culture influenced area,while the moderately affected areas accounted for 20.1% of Yangshao culture influenced area.Meanwhile,92% of the land areas on the edge and outside of the Yangshao culture influenced area were not affected by human activities.The arbor pollen in these areas did not decrease until 4.0 ka BP.     

Current situation and trend of arable land change in China

IntroductionAlmost all the developing countries have experienced the decrease of cultivated land in the process of population growth, economic development and urbanization. The situation is more serious in China because of the huge amount of population and relative limited arable land. From 1986 to 1995, the cultivated land has decreased nearly 7 million hectares, the amount of annual decrease is 0.7 million hectares in China according to the available statistical data. But the real situation…