Cropland redistribution to marginal land has been reported worldwide; however, the resulting impacts on environmental sustainability have not been investigated sufficiently. Here we investigated the environmental impacts of cropland redistribution in China. As a result of urbanization-induced loss of high-quality croplands in south China (∼8.5 t ha–1), croplands expanded to marginal lands in northeast (∼4.5 t ha–1) and northwest China (∼2.9 t ha–1) during 1990–2015 to pursue food security. However, the reclamation in these low-yield and ecologically vulnerable zones considerably undermined local environmental sustainability, for example increasing wind erosion (+3.47%), irrigation water consumption (+34.42%), fertilizer use (+20.02%) and decreasing natural habitats (−3.11%). Forecasts show that further reclamation in marginal lands per current policies would exacerbate environmental costs by 2050. The future cropland security risk will be remarkably intensified because of the conflict between food production and environmental sustainability. Our research suggests that globally emerging reclamation of marginal lands should be restricted and crop yield boost should be encouraged for both food security and environmental benefits.

It is important to study the contributions of climate change and human activities to cropland changes in the fields of both climate change and land use change. Relationships between cropland changes and driving forces were qualitatively studied in most of the previous researches. However, the quantitative assessments of the contributions of climate change and human activities to cropland changes are needed to be explored for a better understanding of the dynamics of land use changes. We systematically reviewed the methods of identifying the contributions of climate change and human activities to cropland changes at quantitative aspects, including model analysis, mathematical statistical method, framework analysis, index assessment and difference comparison. Progress of the previous researches on quantitative evaluation of the contributions was introduced. Then we discussed four defects in the assessment of the contributions of climate change and human activities. For example, the methods were lack of comprehensiveness, and the data need to be more accurate and abundant. In addition, the scale was single and the explanations were biased. Moreover, we concluded a clue about quantitative approach to assess the contributions from synthetically aspect to specific driving forces. Finally, the solutions of the future researches on data, scale and explanation were proposed.

耕地集约利用是保障粮食安全、提高农业经济效益、增加农民收入的重要手段,在面对日益复杂的人地关系以及社会经济发展变化过程中,如何通过破解土地、劳动力、资金与技术难题来探究耕地集约利用转型是土地资源科学亟需解决的重要议题,这对于促进耕地资源优化配置、农业转型发展和质量兴农具有重要的理论和现实意义。鉴于此,本文运用文献回顾和综合归纳法,基于耕地利用系统理论,从要素替代视角分析耕地集约利用转型内涵,进而剖析耕地集约利用转型的动力机制、演化阶段与特征,并提出转型优化调控途径。结果发现：①耕地利用系统是指农业生产经营参与者在一定数量和质量的耕地上通过投入适量的劳动生产要素而获得农产品及社会经济效益的自然-人工复合系统。由耕地利用系统要素和结构优化调整转变而引发的耕地利用系统演化对研究耕地集约利用转型的本质具有借鉴意义。②耕地集约利用转型是指耕地利用系统的要素和结构随着自然地理、社会经济等外部环境变化而不断调整变化后呈现出的趋势性转折。耕地集约利用转型的演化过程是：劳动集约型阶段—资金集约型阶段—技术集约型阶段,具有一定持续性和阶段性特征。③耕地集约利用转型动力机制包括：耕地、劳动力、农业物资、技术等耕地利用系统内部不同要素价值和价格非同步演变机制与各要素相互替代和重组机制,以及产权赋能与合理收益分配制度的联合反馈机制。因此,本文认为,助推耕地集约利用转型可以通过促进耕地增值、调整耕地利用主体、对农业生产进行补贴等途径进行综合调控。

Farmland intensive use is the key to ensuring food security, improving agricultural economic benefits, and increasing farmers' income. Farmland intensive use transition is an important issue that needs to be examined urgently in land resources science. Analyzing the factors of land, labor, capital, and technology has important theoretical and practical significance for promoting the optimal allocation of arable land resources, agricultural transformation and development, and quality agriculture. Based on the theory of farmland use system, this study used literature review and comprehensive induction to analyze the connotation of farmland intensive use transition from the perspective of factor substitution; the dynamic mechanism, evolution stage, and characteristics of farmland intensive use transition; and ways to optimize the regulation and control of farmland intensive use transition. The results show that: (1) Farmland use system is a natural-artificial composite system in which agricultural operators obtain agricultural products and benefits by inputting labor and production factors on farmland. The study on the transition of farmland intensive use can benefit from studies on the evolution of farmland use system. (2) The transition of intensive use of farmland refers to the trend transition of the elements and structure of the farmland use system as the external environment changes. The evolutionary process of the transition of intensive use of farmland is labor intensive stage capital intensive stage technology intensive stage, which has certain continuity and stage characteristics. (3) The dynamic mechanism of the transition of intensive use of farmland includes the non-synchronous evolution mechanism of the value and price of different elements, the mutual substitution and reorganization mechanism of each element, and the joint feedback mechanism in response to the perfect property rights. Therefore, it is necessary to carry out comprehensive regulation in terms of promoting the value-added of farmland, adjusting the main subjects of farmland utilization, and subsidizing agricultural production.

基于“理性小农”、超边际经济学等理论,建立了农户耕地集约利用解释的理论框架。构建了集约利用度指数 (CII) 和驱动力模型,分析了1996-2008年中国省域的耕地集约利用程度及其影响因素。研究结果表明：我国耕地利用集约度总体大幅度提高,但地域差异明显,初步形成了第一阶梯较高集约度、第二三阶梯较低集约度的空间格局;耕地集约利用的首要贡献来自于化肥、机械、农药等省工性劳动的大量使用,其次是资本投入和劳动力;耕地自然本底条件、耕地经济收益和劳动力生产率,与耕地集约度呈正相关,而耕地非农化效益与耕地利用集约度呈负相关。基于研究结论的政策引申：加强政策引导,科学合理使用非可再生能源等省工性劳动;切实改善农业生产条件,适度规模经营,提升劳动生产率和耕地综合生产力;提高耕地经营性经济补贴标准,激励农户稳定从事农业生产的积极性。

The aim of this study is to establish several important factors representing the land-use intensification in the cultivated land (denoted by CII) using a multi-dimensional approach for achieving realistic and practical cultivated land use policies. For this reason, the theoretical framework was firstly built to explain the changes of land-use intensification in the cultivated land, and then the variables and index were further developed for characterizing the dynamic trends and driving forces of the land-use intensification in the cultivated land at provincial level. Results indicate that the extent of CII obviously increased during the period from 1996 to 2008 due to the extensively use of fertilizers, machinery and pesticide, the increased labor and capital input as well as the intensified land use. Moreover, the principal component regression results show that the productivity of cultivated land, the economic benefits of cultivated land, the labor productivity and the land use conversion are the main factors affecting the village development. The first three factors play a positive role while the last one produces a negative effect on the land-use intensification in the cultivated land. According to these results, main policies for sustainable intensification in cultivated land are formulated. Firstly, the sustainable pathways for intensification should be adopted to reduce the unsustainable uses of chemical fertilizer, agricultural chemicals and etc. Secondly, the condition for agricultural production should be further improved to increase the cultivated land productivity. Thirdly, it is necessary and helpful for improving labor productivity and land use efficiency from the viewpoint of speeding up the cultivated land circulation.

本文基于中分辨率卫星遥感数据,深入分析了2000-2010年间中国耕地变化及其空间差异,并对中国耕地占补平衡政策的实施效果进行了评估。结果表明：10年间中国耕地面积有所减少,由2000年的1.85亿hm²,减少到2010年的1.81亿hm²,耕地减少的主要方式为耕地转为城镇建设用地。耕地变化在空间上呈现出西增东减,北增南减,东部沿海自然条件良好地区以及中部生态环境脆弱地区耕地减少,西部水资源缺乏地区耕地增加的基本格局。大部分省份没有实现耕地占补平衡基本目标,有18个省份占补平衡指数小于-50％。建设占用的耕地多适宜农业耕作,而新增耕地只有不到一半适宜农业耕作。研究时段内经济快速发展、人口增加以及城镇化等因素导致的建设用地需求快速增加,决定了东部地区耕地占补平衡很难有效实施。全国耕地总体占补平衡背后存在较为严重的生态风险,耕地增加过于依赖土地开发,对现有耕地的保护亟待加强。

地形是影响人类生产和生活的重要环境因子之一, 也是影响土地资源结构及其变化的重要因素之一。本文基于全国地形数据和2008年-2010年土地利用动态变化数据, 以占补耕地的海拔、坡度以及破碎度为主要参数, 分析近年来中国占补耕地的地形分布特征。结果表明:①2008年-2010年, 全国耕地占补呈现南占北补的空间分布格局, 黑河-腾冲线以西以补充耕地为主, 而黑河-腾冲线以东以占用耕地为主。其中新疆耕地补充较多, 占全国补充耕地的76.8%, 长三角、京津冀等地区耕地占用较为严重。甘肃、内蒙古、黑龙江等北方城市占用与补充耕地交错分布, 在数量上基本达到占补耕地的动态平衡;②我国耕地重心向西北方向移动。耕地占用主要发生在华北、华中等地区, 而补偿耕地主要在北方以及西北地区。从各省的情况看, 产粮大省耕地占用较多, 补偿不到位, 且占用耕地地形要素较为优越, 而补充耕地地形要素较差不利于农作物生长, 如若不引起重视会对我国的粮食安全产生威胁;③从占补耕地的地形分布特征来说, 全国38.7%的省份占用耕地的坡度小于全省耕地的平均坡度, 而补偿耕地的平均坡度大于全省耕地的平均坡度, 海拔、破碎度与耕地占补的关系也表现出与坡度类似的特征。这说明, 我国在城市化加速的进程中, 优质耕地资源存在被占用的情况, 而在对耕地资源进行补偿的过程中, 往往不能做到等质等量的耕地补偿, 尤其是当占用了大量连片耕地时, 补偿过程以零散地块补偿为主, 大大削弱了耕地的生产能力, 降低了耕地的规模化生产价值, 增加了农业的投入产出比

Terrain is one of the most important environmental factors affecting human life, production, land resource structure, and changes in these. Based on topographic data and land use dynamic change from 2008 to 2010 we analyzed China’s terrain features related to occupation and supplemental cropland using elevation, slope, and degree of fragmentation. We found a spatial distribution pattern of occupation cropland in southern China and supplemental cropland in northern China. The Heihe-Tengchong line still plays an important role, to the west of the line supplement cropland was more common than occupation cropland, while east of the line the opposite is true. Xinjiang had more supplemental cropland, accounting for 76.8% of the supplemental cropland in China. The occupation of cropland in the Yangtze River Delta, Beijing-Tianjin-Hebei and other areas is serious. Occupation and supplement cropland of Gansu, Inner Mongolia, Heilongjiang and other northern areas are interlaced in distribution and almost in dynamic balance. The barycenter of cropland moved northwest, from the view of China’s cropland dynamic change characteristics. China's cropland occupation occurred mainly in northern and central China, while supplemental cropland is mainly in northern and northwest China. Provinces that produced large quantities of food occupied more cropland, but supplement was not in place. The terrain elements of occupation cropland are of better quality, while terrain elements of supplement cropland are poorer quality and not conducive to the growth of crops. From topographical distribution characteristics of occupation-supplement cropland, the slope of occupation cropland is less than the average slope of the cropland across the province. The slope of supplemental cropland was above the average slope of the provincial cropland for 38.7% of provinces. Relationships among elevation, fragmentation degree and occupation-supplement cropland followed a similar pattern to that found for slope. China occupies a large number of high quality cropland resources in the process of accelerated urbanization, and cannot supplement the same amount and quality of cropland in the process of cropland compensation. Supplemental cropland occurs mainly as scattered plots and this greatly weakens the production capacity of cropland, reduces the large-scale production value of cropland, and increases the agricultural input-output ratio.

研究占补耕地光温生产潜力的时空特征对指导耕地资源开发与粮食生产具有重要意义。论文基于1980年代末—2010年的多期土地利用和多年平均光温生产潜力,以占用耕地与增补耕地单位面积光温生产潜力为依据,分析20 a来中国占补耕地光温生产潜力时空特征,并进一步探讨其对光温生产潜力总量的影响。结果表明:①1980年代末—2010年,全国耕地存在明显的占优补劣情况;②从各分区看,东北平原主产区、北方干旱半干旱主产区、青藏高原区、华南主产区、云贵高原区占用耕地单位面积光温生产潜力持续高于增补耕地,长江中下游主产区占用耕地单位面积光温生产潜力持续低于增补耕地,四川盆地及周边地区、黄土高原区、海南由占优补劣变为占劣补优,黄淮海平原区由占劣补优变为占优补劣;③占优补劣对全国光温生产潜力总量变化有显著影响;④东北平原主产区等我国耕地开垦的主要区域受占优补劣的影响较大,华南主产区等耕地损失区受占优补劣的影响相对较小,占劣补优对缩小耕地占用对光温生产潜力总量影响的作用并不大。

It is of great significance to study the light-temperature potential productivity (LTPP) on cropland occupation and supplement for reasonable developing cropland resources and instructing grain production. This paper analyzed spatial-temporal characteristics of LTPP on cropland occupation and supplement for recent 20 years in terms of LTPP per unit area based on multiperiod land use change data and average annual LTPP from 1990 to 2010. The results demonstrate: 1) LTPP per unit area on cropland occupation was higher than on cropland supplement at country level from the 1980s to 2010. 2)At regional level, LTPP per unit area on cropland occupation was continuously higher than on supplement in the last 20 years in producing areas of Northeast China Plain, arid and semiarid northern China, Qinghai Tibetan Plateau, South China and Yunnan-Guizhou Plateau. Cropland with lower LTPP per unit area was occupied and cropland with higher LTPP per unit area was supplemented in the middle and lower reaches of the Yangtze River. LTPP per unit area on occupation was higher for the former 10 years but however, lower for the latter 10 years in Sichuan Basin and the surrounding area, the Loess Plateau, and Hainan. The cropland with higher LTPP per unit area was supplemented for the former 10 years and occupied for the latter 10 years in Huang-Huai-Hai Plain. 3)Better cropland occupied and worse cropland supplemented had an important effect on total LTPP at country level. 4)The regions (Northeast China Plain, etc.), with a greater deal of cropland supplement than occupation were remarkably affected by better cropland occupied and worse cropland supplemented, which had a slight effect on the regions (South China and so on) with a greater deal of cropland occupation than supplement. Better cropland supplied than worse cropland occupied also slightly impacts the regions (the middle and lower reaches of the Yangtze River and so on) where more cropland was occupied and less cropland was supplemented.

20 世纪90 年代以来的快速城市化进程和1999 年开始启动的退耕还林草生态工程对耕地的分布与生产能力产生了重要影响。本研究应用由TM 遥感影像获取的1980s-2000 年与2000-2005 年两个时间段耕地变化数据,结合以多时相遥感数据为主要数据源的耕地生产力光能利用率遥感模型估算两个研究时段耕地生产力变化特征,比较城市化与退耕还林草政策主导下两个时期耕地转移对各区域耕地生产力的影响。研究结果表明:两个研究时段因城市占用损失的耕地生产力占土地利用变化(LUCC) 导致的耕地生产力减少总量比例均在60%以上。在20 世纪90 年代,全国新增耕地生产力总量比被占用耕地生产力高87%,耕地转移使中国耕地生产力增加。2000-2005 年间,退耕还林草政策的启动和快速城市化进程对耕地的持续占用导致耕地生产力占补正平衡指数由前一时段的正平衡变为负平衡,转出耕地生产力总量比新增耕地生产力高31%,耕地转为林草地和建设占用损失的耕地生产力分别较前一时段提高57%和85%。城市化与退耕还林草政策等驱动因素作用下耕地开垦区与占用区的空间分布差异使得耕地生产力占补平衡状态和趋势呈现明显的区域分异。

In this study, the changes of agricultural production from cropland transformation in the periods of the late 1980s-2000 and 2000-2005 were estimated based on: 1) the cropland transformation results derived from Landsat TM imagery by artificial interpretation method, and 2) net primary productivity (NPP) data from the light use efficiency models of Global Production Efficiency Model (GloPEM) and Vegetation Photosynthesis Model (VPM). Changes of regional grain production capacity were mainly from two aspects of cropland transformation: cropland conversion (e.g. urbanization, converting cropland into forest) and land reclamation (e.g. converting grassland into cropland). The impacts of different cropland transformation types on agricultural production within the two periods were evaluated, a series of comparisons were conducted between the two periods as well as different regions. Results indicated that the agricultural production loss due to urban sprawl accounted for more than 60% during both stages (1980s-2000 and 2000-2005) in the total loss. In the first stage, generally, agricultural production increased evidently. The increased production from land reclamation was 87% higher than production decrease from cropland conversion. However, in the second stage (2000-2005) the agricultural production loss due to cropland conversion was 31% higher than the production increase from land reclamation, in other words, the production decrease due to cropland loss could not be compensated by limited land reclamation, as unban expansion and Grain for Green (GFG) project played an important role in cropland transformation since around 2000. Production losses from GFG project and urbanization were 57 % and 85 % higher than that in the previous stage, respectively. Due to GFG project, the states of agricultural production equilibrium changed from positive balance from the 1980s to 2000 into a negative balance during 2000-2005. the loss of agricultural production mainly occurred in Northeast China, Inner Mongolia, Yunnan and Zhejiang provinces from the 1980s to 2000, and then transferred to Inner Mongolia, Shaanxi, Gansu, Sichuan and Guizhou provinces from 2000 to 2005. The production loss due to urbanization mainly occurred in Jiangsu, Hebei, Anhui, Shandong, Henan and Guangdong provinces from the 1980s to 2000, then changed into provinces of Zhejiang, Guangdong, Shandong, Fujian and Jiangsu during 2000-2005. The land reclamation foci transferred from Northeast China to Northwest China in the two stages, the greatest contribution regions to agricultural production shifted from the Xinjiang Uygur Autonomous Region from the 1980s to 2000 into Heilongjiang Province during 2000-2005. Due to the cropland transformation from urbanization and GFG project, two thirds of provinces showed a significant change in agricultural production balance state in the two stages.

Based on the statistic data of agriculture in county-resolution for the time period of 1985-1987 and 2002-2004, the changing regional distribution of grain productivity in China in recent 20 years has been examined in this paper. It is found that, 1) grain productivity indicated by grain yield per unit cropland has increased in most parts of China, especially in the west to the farming-grazing transitional zone, which has played more important role on total grain yield increase in the past 20 years in China. 2) the differences of a grain productivity dominated by rainfall between the eastern and western China have remained obviously up till now. But the south-north difference of grain productivity dominated by temperature in the eastern China has reduced for the sensitive increase in grain productivity in the northern China. The lowest grain productivity zone is located in the farming-grazing transitional zone where the precipitation is 250-400 mm. East to the lowest zone, grain productivity has raised gradually from the northwest to the southeast which may be divided in higher grain productivity zone and the highest grain productivity zone. But the gradation of grain productivity in the east became less obvious in the period of 2002-2004. West to the lowest zone, named the lower grain productivity zone, the relative increase of grain productivity was faster than that in the lowest zone and east to the lowest zone. 3) The area of cultivated land has expanded obviously in the western China, where the grain productivity is lower but increased fasty. While high quality cultivated lands reduced. There are positive impacts of climate change on the increase of grain productivity in Gansu and Xinjiang region, the middle-east of Inner Mongolia and Northeast China, where the temperature has risen significantly and the precipitation in most regions of western China has increased slightly in recent 20 years. 4) The regions, of which the grain productivity ranks the top and bottom in China, both have the higher decrease of the cultivated land and the multi-cropping index as well. The average annual decrease of multi-cropping index is more than 1%-2%. The reduction of multi-cropping index went with the decrease of the cultivated land in the middle-down stream and the southward region of the Changjiang River of the highest grain productivity region implies the lost of the highest quality cultivated lands and the increase of food security risk. While in the lowest grain productivity region, especially in ecological sensitivity regions, such as the region along the Great Wall and the western Sichuan, the implement of the policies for recovering forest and grass in the cultivated land is attributed to the decrease of cultivated lands and it would benefit to ecosystem health and soil protection.

粮食是社会经济发展的重要保障。运用耕地、粮食安全测度模型对2005~2014年河南省粮食安全状况进行评估。结果表明：① 2005~2014年,农民种粮积极性上升10%,耕地压力指数下降71%,农民经济收益上升 13%,耕地重心向西南移动。 ② 不同指标对耕地生产力的贡献率具有差异性。2005~2009年粮种比对耕地生产力的贡献率最大,2010~2014年贡献率发生转移,粮食播种面积单位产量对耕地生产力的贡献率最大;10 a间,粮种比的贡献（69.77%）相对粮食单产的贡献（39.28%）更能促进河南省耕地生产力的提高。 ③ 耕地压力受到自然、社会等多方面因素影响。各指标间相关关系较强,种粮积极性与农民耕地保护能力的二者呈现负相关关系。

Food is the important guarantee of the social and economic development. By taking the Henan Province agricultural data (2014-2015) as the indicator layer, this article assessed the food security in Henan Province by using standard cultivated land coefficient model, food resources carrying capacity, cultivated land pressure index model and food safety driving force model. The results showed that: 1) From 2005 to 2014, the overall cultivated land productivity increased steadily, the farmers’ enthusiasm for growing grain increased by 10% in study area, the pressure index of cultivated land decreased by 71%, the farmers’ income increased by 13%, and the gravity center of the cultivated land showed a southwest movement trend. It’s that cultivated land resource in 10 years appeared in the southwest area of cultivated land resource is higher than the northeast, the southwestern cities of cultivated land resources protection weak in northwestern region of Henan Province; 2) Between 2005 and 2009, the contribution rate of planting ratio of grain to the arable land productivity in Henan Province was 80.61%; In 2010-2014, contribution rate extreme value transferred to grain yield per unit, and its contribution rate was 100.37%; Compared with grain yield per unit area, planting ratio of grain had a leading role in improving the productivity of cultivated land in Henan Province. In addition, overall situation of cultivated land productivity will increase steadily, and cultivated land pressure coefficient and standard has obvious negative correlation between cultivated land coefficient, cultivated land pressure index space distribution in northern and eastern pressure is low, cultivated land pressure decrease gradually from west to east; 3) Fertilizer input, the farmers' enthusiasm for growing grain and protection ability of cultivated land had a strong coupling relationship with food security; However, the farmers’ enthusiasm for growing grain and protection ability of cultivated land presented a negative correlation. High cultivated land pressure index of Zhengzhou and Sanmenxia is the result of social and economic elements and natural geographical environment. In terms of Zhengzhou, the limited urban area within the scope of regional economic development, get more economic benefit, is the important foothold of its development. In terms of unit efficiency, the unit of second and third industry output value is much higher than the first industry, cultivated land become one of main way to obtain higher economic benefits. The behavior of lead to Zhengzhou City since 2005 cultivated land pressure index is high, and the food security situation showed a trend of deterioration.

基于IPAT和IBIS模型在预测人为碳排放和陆地生态系统碳汇的基础上,探讨了中国2060年实现碳中和的可行性以及不同土地利用方式承载的碳汇分布。2060年我国人为碳排放预计为0.86 Pg C yr ^-1;IPCC报告中RCP 2.6和RCP 6.0情景的陆地生态系统分别中和33%和38%的人为碳排放。2060年林地、草地、耕地是陆地生态系统碳汇主要贡献者,占93%;与2030年比,在RCP 2.6情景下林地和草地的碳汇贡献分别下降10%和8%,而耕地上升18%;RCP 6.0情景下林地和草地的贡献分别下降7%和2%,而耕地上升4%。但若按2051—2060年间两种情景下的最高年份（2055年）的碳汇计,则分别可以中和65%、82%的人为碳排放。据此,提出为实现2060年碳中和,应以碳承载力为基础,聚焦区域国土空间规划和建设用地开发规模,对土地利用转变进行严格管控,探索制订土地利用碳排放标准。

以1980年、2000年、2015年土地利用类型、NPP和统计数据为基础,运用GIS和生态系统服务价值测算方法,分析京津冀食物生产与固碳释氧两种服务的变化及其空间格局,揭示“生态系统服务转型”的原因。结果表明:（1）35年来,京津冀土地利用变化以建设用地扩张和耕地减少为主。1980年和2000年,NPP的高值区主要位于山区,2015年NPP的高值区主要位于平原。（2）1980-2000年京津冀生态系统服务变化以食物生产服务增加与固碳释氧服务降低为主,2000-2015年京津冀以食物生产服务与固碳释氧服务同时增加为主。“生态系统服务转型”模式为“食物生产+固碳释氧–”→“食物生产+固碳释氧+”。（3）农业生产力提升、林地面积与质量和耕地质量、草地质量提升是“生态系统服务转型”的主要原因。

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a 14-channel imaging instrument operating on NASA’s Terra satellite since 1999. ASTER’s visible–near infrared (VNIR) instrument, with three bands and a 15 m Instantaneous field of view (IFOV), is accompanied by an additional band using a second, backward-looking telescope. Collecting along-track stereo pairs, the geometry produces a base-to-height ratio of 0.6. In August 2019, the ASTER Science Team released Version 3 of the global DEM (GDEM) based on stereo correlation of 1.8 million ASTER scenes. The DEM has 1 arc-second latitude and longitude postings (~30 m) and employed cloud masking to avoid cloud-contaminated pixels. Custom software was developed to reduce or eliminate artifacts found in earlier GDEM versions, and to fill holes due to the masking. Each 1×1 degree GDEM tile was manually inspected to verify the completeness of the anomaly removal, which was generally excellent except across some large ice sheets. The GDEM covers all of the Earth’s land surface from 83 degrees north to 83 degrees south latitude. This is a unique, global high spatial resolution digital elevation dataset available to all users at no cost. In addition, a second unique dataset was produced and released. The raster-based ASTER Global Water Body Dataset (ASTWBD) identifies the presence of permanent water bodies, and marks them as ocean, lake, or river. An accompanying DEM file indicates the elevation for each water pixel. To date, over 100 million 1×1 degree GDEM tiles have been distributed.

中国复杂的自然要素、社会经济要素、区域发展战略和政策调控形成了当前中国不均衡的经济发展空间格局、土地利用空间格局和生态环境质量空间格局。厘清中国生态环境质量的空间格局及形成机理对中国土地资源的可持续利用和生态环境的有效保护具有重要的实践意义和价值。以往研究缺乏对中国县域尺度土地利用/土地覆被变化生态环境效应的空间分异性及形成机理的相关研究,本研究基于1995—2015年间中国土地利用现状遥感监测数据,尝试采用生态环境质量指数方法测度中国土地利用变化的生态环境效应,并且综合运用重心分析、热点分析工具（Getis-Ord G_i*）和地理探测器等研究方法,分析1995—2015年中国生态环境质量时空演变特征及形成机理。研究结果如下：① 东部季风区生态环境质量指数高于青藏高寒区和西北干旱区,东部季风区生态环境质量低值区主要分布在人口和经济集聚的城市群以及省会城市周边地区。研究期间中国生态环境质量重心持续向西北方向迁移;② 1995—2015年间中国生态环境质量变化的热点区域主要分布在西藏地区、新疆、重庆、贵州以及位于黄土高原的省份（青海、甘肃、宁夏、内蒙古、山西、陕西以及河南）境内,冷点区域主要分布在长江经济带沿线地区省份以及东南部沿海地区省份;③ 土地利用程度对于生态环境质量影响力显著强于其他因子,东部季风区的社会经济和交通区位因子对生态环境质量影响力强于青藏高寒区、西北干旱区和生态大区过渡带;④ 影响因子之间相互作用主要包括非线性增强作用和双因子增强作用两种类型,以非线性增强作用为主。

The complex physical elements, socioeconomic elements, regional development strategies, and policy adjustments have formed China's current unbalanced spatial economic development pattern, spatial land use pattern, and spatial eco-environmental quality pattern. The unclear eco-environmental quality formation mechanism would limit the sustainable land use and the effective conservation of the ecological environment in China. Few studies have examined the spatial heterogeneity and the formation mechanism of China's eco-environmental quality at the national scale. This paper uses the eco-environmental quality index method to measure the eco-environmental effects of land use/land cover change (LULCC) to provide an overall review of eco-environmental quality index under complex physical and socioeconomic circumstances in China. We analyze the spatiotemporal evolution features and formation mechanism of eco-environmental quality from 1995 to 2015 with the gravity center analysis method, hot-spots analysis tool (Getis-Ord G_i*), and Geo-detectors tool. The results are as follows: (1) The eco-environmental quality of the eastern monsoon region is higher than that of the alpine region of the Qinghai-Tibet Plateau and the arid region of northwest China. The low-value regions of the eastern monsoon region are mainly distributed in urban areas with dense population and economic agglomeration. The gravity center of eco-environmental quality during the study period moves toward the northwest of China continuously; (2) The hot-spots areas of eco-environmental quality change during 1995-2015 are mainly distributed in Tibet, Xinjiang, Chongqing, Guizhou, and the provinces located in the Loess Plateau (Qinghai, Gansu, Ningxia, Inner Mongolia, Shanxi, Shaanxi, and Henan). The cold-spots areas are mainly distributed in the provinces along the Yangtze River Economic Belt and the coastal regions in the southeast of China. The cold-spots and hot-spots changes in China's eco-environmental quality are closely related to the regional development strategies and the implementation of ecological conservation projects in China; (3) Land use intensity has a stronger effect on the eco-environmental quality than other factors, and the impacts of socioeconomy, traffic road, geographic location in the eastern monsoon region are stronger than those in the alpine region of the Qinghai-Tibet Plateau and the arid region of northwest China; (4) The interactions between physical elements and socioeconomic elements are stronger than the interactions within individual indicators. The interactions between the influencing factors mainly include nonlinear enhancement and bi-factor enhancement, and nonlinear enhancement is the dominant interaction mode.

城镇建设用地规模与结构变化是国土空间开发与规划研究的基础。以往相关研究更关注建设用地水平空间扩张格局特征与模式,极少关注建设用地三维梯度上的“爬坡”特征规律与影响。因此,本文基于Google Earth Engine（GEE）,并结合高精度地形数据与土地利用数据,在建设用地坡谱概念基础上,首次构建了平均建设用地爬坡指数（ABCI）,系统地分析了1990—2018年中国建设用地坡谱在国家、区域、省级和城市4个尺度上的变化特征与规律并深入剖析建设用地爬坡的空间影响。结果显示：① 1990—2018年中国坡度5°以上地区建设用地面积增长了1.43倍,比例由10.25%上升至14.81%。其中2010—2015年是建设用地爬坡发展最迅速与规模最大的时期,且中西部地区建设用地爬坡最为显著。② 依据平均建设用地爬坡指数与上限坡度变化,可将中国34个省（自治区、直辖市）划分为高爬坡型、低爬坡型和水平扩展型3类,其中高爬坡型省份占50%以上,水平扩展型省份仅有7个,在空间上呈现“东南—西北”的两极分布特征。③ 1990—2010年爬坡型城市以山地与丘陵地貌城市为主,2010年后少数民族聚居区及低丘缓坡开发试点城市成为建设用地爬坡的主力。④ 建设用地爬坡在一定程度上能够减少建设用地扩张对平原优质耕地与生态用地的胁迫和侵占,缓解建设用地供需矛盾,但是无规划约束的开发和房地产驱动的“削山造地”则会导致地质灾害和生态环境风险的增加。

The changes in the scale and structure of built-up land is the basis for spatial development and planning of the national territory. Previous studies mainly focused on the characteristics and patterns of the horizontal expansion of built-up land, but little attention has been given to the "three-dimensional" gradient characteristics and effects of built-up land (such as slope-climbing). Therefore, based on Google Earth Engine, this study, for the first time as far as we know, uses DEM and land use data to draw built-up land slope spectrums and calculates the average built-up land climbing index (ABCI). The gradient characteristics and laws of the slope climbing of China's built-up land from 1990 to 2018 at the national, regional, provincial, and urban scales are systematically analyzed and the various spatial effects are explored. The results show that: (1) From 1990 to 2018, the area of built-up land with slope angle above 5° in China increased by 1.43 times, and the proportion of the total built-up land area rose from 10.25% to 14.81%. Particularly, the 2010-2015 period witnessed the fastest and largest slope-climbing development of built-up land in China. Moreover, the slope-climbing intensities in the central and western regions are higher than that in other regions. (2) According to the average built-up land climbing index (ABCI) and the upper limited slope angle change (ULSC), the 34 provinces (autonomous regions and municipalities) in China can be divided into three types: high-climbing, low-climbing, and horizontally expanding. Among them, the number of high-climbing provinces accounts for more than 50% of the total. And seven horizontally-expanding provinces present the distribution characteristics of "southeast-northwest" in space. (3) Before 2010, the cities with slope-climbing phenomenon were mainly mountainous cities. However, ethnic minority settlements and low-hill and gentle slope development pilot cities became the main force for the slope-climbing of built-up land after 2010. (4) The slope-climbing of built-up land can reduce the occupation of plain arable land and ecological land by built-up land expansion to a certain extent, and thus alleviate the contradiction between supply and demand of build-up land. However, it is worth noting that development and construction without reasonable plans and bulldozing mountains to build cities driven by real estate can also lead to increased geological disasters and ecological risks.

以西双版纳为研究区，基于生态系统服务和生态敏感性，采用热点分析法提取出生态源地，构建景观破碎化综合指数修正地物赋值的阻力系数，基于MCR模型识别出生态廊道和生态节点，构建和优化西双版纳的生态安全格局。结果表明：1）重要生态源地20个，总面积为7 709.56 km²，占西双版纳州面积的40.33%。2）与夜间灯光数据校正的阻力面相比，基于景观破碎化指数修正的景观阻力面空间分异更加显著，且在廊道空间分布、避开人类活动冲突区、网络连接度和廊道对比验证上效果较好，说明基于景观破碎化校正的阻力面在夜间灯光数据较弱的区域具有较强的适用性。3）生态廊道包括631.73 km的潜在廊道和278.59 km的关键廊道，呈现大半环和小环状相结合的空间形态；生态节点包括20个资源战略点、4个生态战略点、27个生态暂歇点和24个生态断裂点。4）在现有生态安全格局的基础上，依据现有的自然本底条件和生态格局，优化出“一带一廊四组团”的生态空间结构布局。

Tropical forests are considered the most abundant source of biodiversity in the terrestrial ecosystem and the key to international biodiversity conservation. Due to the rapid process of urbanization and land conflicts, regional ecological security is under tremendous pressure, resulting in biological habitat destruction, ecosystem service degradation, biodiversity reduction, etc. Consequently, the construction and optimization of ecological security patterns can improve ecological environment stability, restore ecological function, and protect biodiversity, which is an important spatial way to solve regional ecological environment problems and improve regional ecological security. In this study of Xishuangbanna, Yunnan Province of China, ecological sources were obtained through ecological system service and ecological sensitivity comprehensive superposition, followed by ecological source extraction through hot spot analysis. The resistance coefficient was modified on the basis of the land cover type through landscape fragmentation comprehensive index construction, and Linkage Mapper calculation was performed to calculate ecological corridors and nodes with the ArcGIS cost-distance analysis module to construct and optimize the ecological security pattern in the Xishuangbanna area. The main results are as follows: (1) Twenty important ecological source areas were extracted from the Xishuangbanna area, covering a total of 7,709.56 km² and accounting for 40.33% of the study area. The coincidence rate with the existing nature reserves is 89.92%, which is mainly distributed in natural reserve areas, such as the northern part of Jinghong City, Central and southern parts of Mengla County, and the southern part of Menghai County. (2) Compared with the resistance surface corrected by night light data, the spatial differentiation of the landscape resistance surface corrected on the basis of landscape fragmentation is more significant. Among this, the identification of ecological corridors, the spatial distribution of the corridors, the reduction of conflict points of human activities, network connections, and optimal corridor verification delivered relatively better results. (3) The ecological corridor, which includes the key corridor and the potential corridor of 278.59 km and 631.73 km, respectively, shows a spatial pattern combined with the half ring and the small rings. Moreover, the ecological nodes include 20 resource strategic points, four ecological strategic points, 27 ecological temporary rest points, and 24 ecological fracture points. (4) By referring to the ecological security patterns of Xishuangbanna area, the layout of the ecological spatial structure was optimized as "one belt, one corridor, and four groups." "One belt" was the ecological river corridor belt with the Lancang River as the main axis and the tributaries on both sides. "One corridor" refers to the central corridor structure connecting the national nature reserves of Mengyang, Naban River, and the Mangao Nature Reserve. Based on the existing nature reserves, the four groups were divided into the Bulong-Mangao nature reserves, Menglun three sub-reserves, Mengla-Yiwu-Mengyang-Menglun nature reserves, and Mengla-Shangyong nature reserves. This study provides a practical case for formulating ecological and environmental protection in Xishuangbanna.

基于2000年、2005年、2010年和2015年土地利用现状遥感监测数据，分别采用景观格局指数和当量因子法测度了黄河流域多尺度景观破碎化和土壤保持服务的时空特征，并且综合运用热点分析工具、普通最小二乘法和空间回归分析模型，探索了2000—2015年黄河流域多尺度土壤保持服务时空演变特征及景观破碎化对土壤保持服务的影响机制。结果如下：① 黄河流域土壤保持服务低值区主要集中分布在黄河流域上游青海-甘肃-宁夏-陕西-内蒙古沿线地区以及流域下游河南和山东，另外省会城市以及周边地区同样是土壤保持服务低值区，土壤保持服务具有显著的尺度依赖性；② 研究期间黄河流域土壤保持服务变化的热点区域主要分布在流域上游黄土高原地区，冷点区域主要分布在黄土高原的周边地区，不同尺度下土壤保持服务变化冷热点差异显著；③ 回归结果显示，经济社会因子与土壤保持服务具有显著的负相关；自然本底因子中海拔和林地面积比重与土壤保持服务具有显著的正相关；景观破碎化指数对土壤保持服务的影响差异性显著。未来黄河流域不同分区土壤保持和土地利用政策的制定不仅需要考虑自然本底和经济社会驱动因子，还应考虑多尺度景观格局破碎化以及空间溢出效应，跨区域协同治理对于黄河流域土地利用政策制定和生态系统保护具有重要现实意义。

Natural ecosystem is increasingly disturbed by the human system. It is of great significance to clarify the influence mechanism of landscape fragmentation on soil conservation services for soil conservation and land use policies formulation in the Yellow River Basin. However, previous studies lacked the studies about the impacts of landscape fragmentation on soil conservation services that considering the spatial dependence at multi-scale comprehensively, which, to a certain extent, limited the effective formulation and implementation of soil conservation and land use policy-making in the Yellow River Basin. This study attempted to measure the spatiotemporal pattern of soil conservation services and landscape fragmentation based on the current situation of land use remote sensing monitoring data in 2000, 2005, 2010, and 2015 using the landscape pattern metrics and equivalent factor method in the Yellow River Basin, respectively. The hot spots analysis tool, ordinary least squares, and the spatial regression models were used to explore the spatio-temporal evolution characteristics of soil conservation services in the Yellow River Basin from 2000 to 2015 at multi-scales and the influence mechanism of landscape fragmentation on soil conservation services. Results are as follows. 1) The low-valued soil conservation services areas in the Yellow River Basin were mainly distributed along Qinghai-Gansu-Ningxia-Shaanxi-Inner Mongolia and the lower reaches of the Yellow River basin in Henan and Shandong. In addition, provincial capitals and surrounding areas were also low-valued soil conservation services areas. Soil conservation services had significant scale dependence. 2) The hot spots of soil conservation services change in the Yellow River Basin were mainly distributed in the Loess Plateau region, and the cold spots were mainly distributed in the surrounding areas of the Loess Plateau during the study period. The spatial patterns of cold and hot spots of soil conservation services change at multi-scale exhibited obvious spatial differences. 3) Regression results showed that the socioeconomic factors had a significant negative association with soil conservation services. In natural background factors, altitude and the proportion of forestland area were significantly positively associated with soil conservation services. Landscape fragmentation metrics had significant influence on soil conservation services, but varied greatly. In the future, soil conservation and land use policy-making in different regions of the Yellow River Basin should not only consider the natural background and socioeconomic drivers, but consider the fragmentation of multi-scale landscape pattern and spatial spillover effect. Cross-regional joint governance is of great practical significance for the formulation of land use policies and ecosystem conservation.