Exploring the key influencing factors of food security guarantee during the typical period is of significance for the development of cultivated land protection and agricultural policy. This paper aims at exploring the factors between 1999 and 2007 which was in the new period of cultivated land protection administration. Methods such as comparison, spatial and econometric analysis are used to analyze the change in cultivated land productivity which was the cause of the disparity between cultivated land area and grain output changes. Results show that farmers' willingness to grow grain which determines cultivated land use intensity is the key factor. The sustained improvement of the willingness in 2003-2007 was mainly resulted from the rise of grain market price. Meanwhile, direct subsidy merely inspired farmers' anticipation for the profit of grain growing at the beginning years of implementing this policy. In addition, suggestions on the development of cultivated land protection are proposed involving improvement of farmers' willingness to grow grain, optimization of inputs in grain growing and improvement of cultivated land protection models.

选取耕地保护“新政”时期的1999-2007 年为研究时段,以耕地面积与粮食产量变化的分歧原因—耕地生产力变化为切入点,通过比较分析、空间与计量分析探寻粮食安全的关键影响因素。结果表明:农民种粮积极性变化决定着耕地集约利用是影响粮食安全的关键;2003-2007 年农民种粮积极性的持续提高主要来自市场粮价的上涨;粮食直补仅在开始实施的年份激发了农民对种粮收益的预期。此外,本文从提高农民种粮积极性、优化粮食生产投入及改进耕地保护模式3方面,提出了耕地保护发展的政策建议。

This paper presents an approach for spatially explicit assessment of food security in consideration of a combination of the biophysical, social and economic factors of food security. To do that, two indicators, i.e., per capita food availability and per capita GDP, were used to cover the four dimensions of food security as many as possible. These two indicators were then linked to three models, i.e., spatial EPIC model, crop choice model and IFPSIM model. This proposed approach was applied to assess food security at a global scale over a period of approximately 20 years, starting with the year 2000. The results show that some regions such as southern Asia and most African countries will likely remain hotspots of food insecurity in the future. Both the per capita food availability and the capacity of being able to import food will decrease between 2000 and 2020. Low food production associated with poverty is thus the determining factor to starvation in these regions, and more efforts are needed to combat hunger in terms of future actions. Other regions such as China, most eastern European countries and most southern American countries where there is an increase in per capita food availability or an increase in the capacity to import food between 2000 and 2020 might be able to improve their food security situation.

在综合考虑自然、社会和经济等因子对粮食安全影响的基础上,选择了人均粮食占有量和人均GDP两个指标空间显性评价全球粮食安全状况。为此,本研究构建了3 个模型,即空间EPIC 模型、作物选择模型和IFPSIM 模型,分别模拟作物单产、作物播种面积和作物价格。利用构建的评价框架和模型,以网格大小为6 分弧度的地理单元为评价对象,选择水稻、 玉米、小麦和大豆等4 类全球主要作物类型,以2000 年为初始年份,对未来2020 年的全球粮食安全状况进行了评价。结果表明,到2020 年,多数南亚国家和非洲国家,由于其人均粮食占有量和人均GDP两个指标值都显著降低,粮食供应不足和贫困一起将可能导致该区域存在 粮食危机和饥饿风险。对于其他区域,日益增长的粮食需求可以通过本区域的粮食生产自给予以满足,或通过外部购买或粮食进口得到满足,总体上不存在粮食安全问题。为保障未来粮食安全,一方面要保护耕地数量和质量、防止土壤退化、增加资本投入、进行技术创新和升级,提高粮食综合生产能力,保障粮食的有效供给;另一方面加大农业补贴,切实提高农民收入,保障农民利益,增强农业购买力。同时,大力改善粮食流通和农产品贸易体制,通 过外部市场来调节粮食供给;积极应对气候变化,提高农业生产对气候变化的适应能力,保证粮食生产的稳定。

China's food security has been a major concern of academic community and governments. The loss of farmland caused by rapid industrialization and urbanization is worrisome. At the same time, the Chinese government upholds the principle of "ensure basic self-sufficiency in grain and absolute security in ration" with the largest population in the world. So how serious a threat is farmland loss to China against the backdrop of continued growth both in grain output and food imports? And how should China respond to the challenge of food security? This paper will provide strong evidences for these issues. With the consideration of labor flow and regional difference, the paper modifies the farmland pressure index properly. Then using a modified farmland pressure index, this paper employs two-step GMM to estimate farmland pressure index on grain output based on the provincial panel data during 2000-2012. We find that farmland pressure index has a strong negative effect on grain output. Moreover, the effect is more obvious in the main producing areas than in non-producing areas. However, by exploring the temporal-spatial variations of China's farmland pressure index, we find that the farmland pressure is declining, and it remains in a safe range. This indicates that there is no serious risk of food security in China under the current urbanization background, and the goals of urbanization and food security are compatible. In the long run, if land policy adjusts properly, Chinese will not only feed themselves, but also will make a contribution to world food security. Therefore, our suggestions are as follows: (1) farmland protection should be combined with the comparative advantage of farmland use: the high quality cultivated land in some regions may demand special protection, such as controlling the scale of urbanization in normal and small cities (towns) properly, promoting the large-scale agricultural operations by subsidies in these areas. And to follow the direction of the agricultural labor flow, the government should encourage the land conversion in metropolises in the eastern region of China to create more jobs for the relief of China's farmland pressure; (2) the purpose of farmland policy adjustment should encourage agricultural scale management.

中国粮食安全问题备受关注,与城镇化背景下耕地资源的减少有关。近年来,中外粮食价格“倒挂”引致的粮食进口量增加进一步加剧了未来中国可能发生粮食安全危机的担忧。与之相关的一个问题是,随着城镇化的推进,中国人能否养活自己?借用广泛使用的耕地压力指数,并对其进行修正,在此基础上,从人均耕地压力的角度重新审视了耕地资源的变动对粮食生产的影响。研究显示：修正耕地压力指数对粮食产量的影响显著为负。不仅如此,这种影响在粮食主产区表现得比非粮食主产区更为明显。同时,通过对修正耕地压力指数的时空演变趋势考察后发现,2000-2012年,中国粮食主产区的修正耕地压力指数始终处于安全压力区并呈下降趋势,表明现阶段耕地资源的减少并没有显著地威胁中国的粮食安全。从长期看,城镇化与保障粮食安全不仅目标是兼容的,如果农地政策调整得当,中国人不但能够养活自己,还能够为全世界的粮食安全做贡献。为此主要建议：耕地保护要以发挥耕地生产力比较优势为原则;农地政策的调整以农业规模化经营为目的。

Food security is a key governmental and academic concern in China. In the past 25 years, due to the rapid industrialization and urbanization, competition for land resources and environmental pollution threatened the sustainability of China's grain production. Studies to date have focused on the urbanized areas, and rural industrial land expansion and impact on food security in China remain largely unknown. This study constructed an 1 km resolution grain output dataset using the latest remote sensing data-derived land use dataset (NLUD-China) and county-level grain production data of China to evaluate the impacts of industrial land expansion and pollution on food security of the country. The results show that the industrial land area increased by 326% between 1990 and 2015, with an increasing expansion rate of 288 km2/a in the 1990s to 2600 km2/a in 2010-2015, close to the current urban expansion rate (3000 km2/a). During 1990-2015, industrial land expansion led to 1.7×104 km2 reduction of crop land, resulting in a direct production loss of 6.49 Mt (106 tons). Indirect losses caused by industrial pollution was conservatively estimated at 83.20 Mt. Overall estimated losses due to industrial land influence can be up to 17% of China's cropland production. Spatially, direct loss of crop production in China decreased from the central and coastal region to the northwest region. In the central and western regions losses caused by soil pollution is relatively serious. With the increasing population and other socioeconomic and environmental changes, the balance between the supply and demand of food becomes more delicate. Therefore, remote sensing monitoring of crop land and industrial land for national macroeconomic development and environmental protection is of great significance.

中国城市化和工业化进程所带来的粮食安全问题一直是政府和学术界关注的焦点。中国近25年来快速的城市化与工业化导致耕地资源减少和环境污染加剧,对国家粮食安全和农业可持续发展产生一定影响。本文基于中国土地利用/覆盖变化最新解译结果和中国分县粮食产量数据,重建了中国1 km分辨率的粮食产量空间数据,分析了中国1990-2015年工矿用地扩张及其对粮食产能的影响。结果表明：中国工矿用地面积在1990-2015年间增长了326%,扩张速率从1990-2000年的288 km²/a增加到2000-2010年的1482 km²/a,近5年(2010-2015年)扩张速率最快,达2600 km²/a。过去25年间工矿用地扩张导致耕地面积减少1.7×10⁴ km²,直接导致粮食产能损失约6.49 Mt(10⁶ t),因工矿用地扩张可能会对周边耕地污染等间接影响的粮食产量达83.20 Mt。经评估,国家工矿用地扩张对粮食产能潜在影响总体上是当前粮食总产能的17%。在空间分布特征方面,工矿用地扩张对粮食产能的直接影响呈现由东部沿海地区向西北地区逐渐减小趋势;间接影响在中部和西部地区相对较大。

Trade of agricultural commodities is an important part of the economic and trade cooperation between the Belt and Road countries, but the existing trade theories cannot fully explain the pattern and change of the cereal trade network between these countries. This study set up a four-dimensional analytical framework, combined social network analysis with spatial econometric analysis, and analyzed the spatial structure characteristics and mechanism of change of cereal trade network between the Belt and Road countries based on the United Nations Comtrade data from 1993 to 2016. The results show that: 1) The cereal trade network density of the Belt and Road countries is constantly increasing while the trade relations and trade intensity between these countries are constantly deepening. The position of the Belt and Road countries in the global grain trade network is on the rise and there is a clear phenomenon of trade club. 2) The network of trade relations has evolved from non-nuclear to multi-nuclear, and then to reshaping. 3) China's cereal trade with other Belt and Road countries has undergone an evolution from export-oriented to import-oriented. The Belt and Road initiative has enhanced China's position in the global grain trade network. 4) The evolution of the national cereal trade network of the Belt and Road countries is the product of resource endowment, economic environment, cultural identity, and political games. Compared with other trade networks, grain trade network has distinct characteristics and stronger stability. This study may provide some guidance for promoting cereal trade cooperation among the Belt and Road countries, optimizing trade structure, and ensuring food security.

农产品贸易是“一带一路”沿线国家间经贸合作的重要内容,但现有贸易理论无法很好地解释“一带一路”国家间粮食贸易网络的格局演化。该文构建了一个四维菱形分析框架,并将社会网络分析与空间计量分析相结合,基于1993—2016年联合国商品贸易数据,分析了“一带一路”国家间粮食贸易网络的空间结构特征及其演化机制。结果表明：① “一带一路”国家间的粮食贸易网络密度不断提高,贸易关系和贸易强度不断加深,在全球粮食贸易网络中的地位呈波动上升态势,并出现明显的贸易俱乐部现象;② 该粮食贸易网络呈现由无核到多核再到重塑的演化历程;③ 中国与其他“一带一路”国家间的粮食贸易经历了从出口导向到进口导向的演化历程,“一带一路”倡议提高了中国在全球粮食贸易网络中的地位;④ “一带一路”国家间粮食贸易网络的演化是受资源禀赋、经济环境、文化认同和政治博弈4个因素共同作用的结果,各因素在不同阶段所起的作用不同;粮食贸易较其他贸易而言特色鲜明,其稳定性更强。研究结果对促进“一带一路”国家农业贸易的健康繁荣,建设开放包容的经济环境具有指导意义。

As important member states of Shanghai Cooperation Organization and key areas of the Silk Road Economic Belt, Russia and Central Asia are gaining a closer and closer relationship with China, which will play a much more important role in ensuring China's geopolitical security and promoting the opening-up of Chinese inland provinces in the future. Under this background, this paper employs Trade Intensity Index, Trade Complementarity Index and Export Concentration Index to depict the dynamics of China's trade with Russia and Central Asia during 1992-2012. Thereafter, the spatial pattern and industrial structure of China's trade with Russia and Central Asia in 2012 are studied thoroughly with special attention paid to the spatial pattern of trade in several key commodities. At last, based on the historical data of China's trade, the authors make a brief predication for the prospects of China's trade cooperation with Russia and Central Asia to the year 2020. The main conclusions are as follows: (1) China's trade intensity and trade complementarity with Russia & Central Asia have been increasing over the past 20 years. Besides, the range of commodities imported from Russia and Central Asia has been extended dramatically. (2) Primary energy and raw materials account for a large proportion in export from Russia and Central Asia to China, while the commodities exported from China to those countries are mainly composed of machinery equipments, textile and clothing. (3) The provincial structure of China's export trade to Russia and Central Asia is the result of a combination of cross-border trade and geographical specialization in China, while China's import trade from those countries is mainly affected by cross-border trade as well as spatial distribution of energy demands. (4) In 2020, the trade volume of China with Russia and Central Asia is expected to exceed 400 billion dollars, among which Turkmenistan will account for a much higher proportion. The commodity structure of China's export will be improved to some extent while that of China's import is more likely to remain the same. Besides, the status of some richer inland provincial units, such as Chongqing, Shaanxi and Sichuan, will be enhanced significantly in China's trade with Russia and Central Asia.

作为上海合作组织成员国及丝绸之路经济带的重点区域,俄罗斯及中亚地区与中国经贸关系日益密切,对中国内陆开放及地缘政治安全具有重大意义。利用贸易强度指数、贸易互补性指数、出口集中指数等,对1992-2012年中国与俄罗斯及中亚地区的贸易发展历程及空间格局、进出口产品格局进行深入分析。结果显示双方贸易强度不断提升,且贸易互补性增强,同时俄罗斯及中亚出口产品种类明显增加。当前双方贸易格局呈现以下特点：俄罗斯及中亚形成了以资源类初级产品为绝对主导的出口产品结构,中国则以机械设备及纺织服装等为主;中国对其出口贸易格局是边境贸易与地区产业专业化格局叠加的结果,进口贸易格局则受边境贸易及能源需求格局的影响。

The discovery, interpretation, and presentation of multivariate spatial patterns are important for scientific understanding of complex geographic problems. This research integrates computational, visual, and cartographic methods together to detect and visualize multivariate spatial patterns. The integrated approach is able to: (1) perform multivariate analysis, dimensional reduction, and data reduction (summarizing a large number of input data items in a moderate number of clusters) with the Self-Organizing Map (SOM); (2) encode the SOM result with a systematically designed color scheme; (3) visualize the multivariate patterns with a modified Parallel Coordinate Plot (PCP) display and a geographic map (GeoMap); and (4) support human interactions to explore and examine patterns. The research shows that such "mixed initiative" methods (computational and visual) can mitigate each other's weakness and collaboratively discover complex patterns in large geographic datasets, in an effective and efficient way.

The research reported here integrates computational, visual, and cartographic methods to develop a geovisual analytic approach for exploring and understanding spatio-temporal and multivariate patterns. The developed methodology and tools can help analysts investigate complex patterns across multivariate, spatial, and temporal dimensions via clustering, sorting, and visualization. Specifically, the approach involves a self-organizing map, a parallel coordinate plot, several forms of reorderable matrices (including several ordering methods), a geographic small multiple display, and a 2-dimensional cartographic color design method. The coupling among these methods leverages their independent strengths and facilitates a visual exploration of patterns that are difficult to discover otherwise. The visualization system we developed supports overview of complex patterns and, through a variety of interactions, enables users to focus on specific patterns and examine detailed views. We demonstrate the system with an application to the IEEE InfoVis 2005 Contest data set, which contains time-varying, geographically referenced, and multivariate data for technology companies in the US.

Since 2018, with the major adjustment of the global political and economic structure, Sino-US relations, which take trade friction as the representation and science and technology competition as the essence, have become increasingly tense. Based on this, this paper characterizes the evolution of global high-tech products trade structure from three aspects of product structure, network structure and influencing factors, and draws some conclusions. First of all, in terms of product structure, global high-tech trade is increasingly concentrated on electronic communication products based on telecommunications equipment. However, on the national scale, chemical products and armament products are not only the dependence products of most countries (regions) on imports, but also the superior export products of most countries (regions). Second, in terms of topology, the global high-tech product trade network continues to expand and is closely linked. It is a typical small-world network and develops a stable "core-edge" hierarchical structure. Third, in terms of spatial structure, the global trade pattern of high-tech products has changed from Europe-North America dominated to East Asia dominated, and also the largest trade country has changed from the United States to China. In addition, the spatial structure has changed from the "double arch" structure with the United States as the core to the "multi-arch" pattern with China as the core, but the United States still occupies a central position in the trade network of various high-tech products. Fourth, in terms of influencing factors, trade scale, economic proximity and cultural proximity have positive effects on the evolution of global high-tech products trade network, while geographical distance has an obvious negative effect. The four factors of political stability, openness, infrastructure and technological innovation only pass the significance test on the importing country (region), while the economic scale only passes the significance test on the exporting country (region). The technological gap is one of the driving forces for the evolution of the global high-tech product trade network.

为清晰刻画全球高科技产品贸易体系变迁,本文利用世界银行以及联合国商品贸易数据库中2000—2017年高科技产品贸易数据,从产品结构、网络结构和影响因素3个方面探讨了全球高科技产品贸易结构的演化态势。研究发现：① 产品结构上,以电信设备为主的电子通讯产品主导全球高科技贸易发展,但在国家尺度上,化学产品和武器产品是大部分国家（地区）的进口依赖产品或出口优势产品;② 拓扑结构上,全球高科技产品贸易网络持续扩张,联系紧密,是一典型的“小世界”网络,并发育出稳定的“核心—边缘”式的等级层次结构;③ 空间结构上,全球高科技产品贸易格局呈现出由欧洲—北美主导向由东亚主导转变,贸易最大国也由美国转变为中国,网络空间结构也呈现出由以美国为核心的“双拱”格局向以中国为核心的“多拱”格局转变,但美国依然在多种高科技产品贸易网络中占据核心地位;④ 影响因素上,贸易规模、经济邻近性和文化邻近性对全球高科技产品贸易网络演化皆具有一定的正向作用,地理距离对全球高科技产品贸易网络的演化起到明显的负向作用。