基于无人机影像的冬小麦深度学习分类

[目的]传统分类方法存在人为主观选择特征、模型无法在大范围泛化的问题,文章利用非监督特征学习的深度学习方法进行冬小麦识别,以解决传统分类方法无法在大范围进行自动化作物识别的不足。[方法]该文集成残差网络(Residual Nets,ResNets)和金字塔场景解析网络(Pyramid Scene Parsing Network,PspNets)构建Res.PspNet,进行冬小麦深度学习自动化分类。在山东全省获取80个村的无人机航拍影像,利用米级遥感影像和对应的标记样本作为"海量标记样本"训练土地覆盖识别模型,以此为基础模型迁移训练冬小麦分类模型,自动提取出冬小麦分布。[结果]实验结果表明,以训练出的土地覆盖数据作为基础模型训练冬小麦模型,收敛速度快,具有很好的泛化性,在不同农业景观调查村中均得到比较准确的结果。从整体验证区域来看,冬小麦总体精度达到了90%以上,区域冬小麦总面积精度达到99%。平原区冬小麦识别精度更高,总体精度达到了90%以上,区域面积精度达到99%,表明模型对冬小麦种植地块规整、生长状态均质的区域,识别精度较高,而山区由于地块破碎、冬小麦长势差异较大,空间卷积会弱化小麦特征且出现"同物异谱"现象,这影响了在该区域内冬小麦的识别精度。[结论]Res.PspNet卷积神经网络能够有效地学习出无人机影像的特征,实现了基于航片影像进行非监督自动化冬小麦"端—端"分类,这也将一定程度上降低冬小麦提取的工作量。     

基于深度学习模型的种植结构复杂区农作物精细分类研究

目的 卫星遥感技术具有覆盖范围广、探测周期短、调查成本低等优势而广泛应用于大区域农作物分类。然而在种植结构复杂区（如城乡结合部）,因其地块破碎、同期生长的作物种类多且分布分散,利用传统的统计分类或机器学习方法进行农作物分类时仍存在精度不高的问题。为提高种植结构复杂区农作物分类精度。方法 文章选取河北省廊坊市广阳区为研究区,以GF-1 PMS全色多光谱融合影像为数据源,采用U-Net、PSPNet及DeepLabv3+,3种深度学习模型进行农作物分类研究。分析模型参数对农作物分类精度的影响,评价3种深度学习模型的农作物分类精度,优选农作物精细分类方法。结果 （1）学习率与3种深度学习模型的分类精度呈正相关关系,较大的学习率（0.01,0.001）下,3种模型收敛速度快,分类精度高。批样本量与模型分类稳定性相关,批样本量设为100时,3种模型的分类稳定性最好。（2）相比PSPNet、DeepLabv3+模型,U-Net模型分类效果最好,总体分类精度为89.32%。（3）GF-1 PMS影像结合U-Net模型可有效提升种植结构复杂区农作物分类精度,大宗作物春玉米、夏玉米的分类精度在80%以上,花生、红薯、蔬菜小宗作物分类精度在60%以上。结论 该研究可为准确获取种植结构复杂区的农作物类型、面积及空间分布信息提供参考依据。     

全国农业资源一张图研制技术探讨

目的 文章围绕全国农业资源一张图生产需求,借助空间大数据处理技术,研究利用2018年度全国土地变更调查县级成果,加工全国及82个绿色农业先行示范区耕地、草地、水域农业资源空间分布图的关键技术和方法,探索全国农业资源一张图生产技术流程。方法 需求分析和软件研发相结合。结果 基于全国统一地理网格框架,设计由2 880个县级土地利用数据库生产集成化全国耕地、草地、水域空间分布栅格图的技术流程,并开发了一体化处理软件平台,形成了全国、2个省、11地市、69县区多尺度耕地、草地、水域等农业资源一张图。结论 综合采用现代空间信息集成技术,利用国家年度土地变更调查县级土地调查数据快速生产全国农业资源（耕地、草地、水域）一张图栅格数据的技术路线可行,且产品质量可靠,可为全国农业资源管理提供较好的基础数据支撑。     

农户农业污染认知对耕地投入行为的影响研究

目的 在农业污染问题日益严重的现实背景下,提高农户农业污染认知水平,引导农户采取合理的耕地投入行为,对于实现农业可持续发展和建设“美丽乡村”具有重要意义。方法 文章首先基于认知行为理论从理论上分析农户农业污染认知对耕地投入行为的影响机理,然后利用粮食主产县湘阴县农户调查数据,运用Tobit回归模型进行实证检验。结果 （1）农户农业污染现状认知、成因认知和政策认知均是影响化学投入品施用量的重要因素,其中,农业污染严重程度、农产品和耕地质量下降状况、农药危害程度、政策了解程度和政府政策满意度均有助于减少化学投入品施用量;（2）受教育程度、非农收入占比、人均承包地面积和承包地质量均对化学投入品施用量产生负向影响。结论 因此,政府应加强农业污染治理的宣传引导,提高农户环保意识,开展农业技术培训,同时通过完善农业污染治理的相关环境规制来调整农户的耕地投入行为,最终达到防控农业污染的目的。     

中国蒸散时空变化规律及其对耕地旱灾影响研究

目的 探究中国蒸散发时空变化规律,揭示耕地蒸散发特征与干旱灾害间的关系,为我国农业干旱灾害预警体系提供参考。方法 文章基于MODIS ET模型,将2001—2018年8天复合遥感数据及每日气象再分析数据输入模型估算陆面蒸散量,分析中国陆面蒸散量时空变化规律;根据土地覆盖类型提取中国耕地地块,探究中国耕地蒸散量变化特征;结合干旱灾害统计数据,揭示我国耕地地表类型中蒸散变化对干旱灾害的作用机制。结果 （1）2001—2018年中国陆地年总蒸散量和年均蒸散量总体呈上升趋势,空间上呈东南—西北逐渐减少的分布特征,高值区位于华南地区和西南地区,其次是华北地区,低值区位于东北地区和西北地区。（2）不同季节、不同月份之间蒸散发差异较大,夏季的蒸散量最高,春、秋次之,冬季蒸散量最小。（3）2001—2017年中国耕地面积呈现先增加后减少的趋势,2004年耕地面积达到峰值1.424亿hm²;截止2017年末,我国耕地面积达到谷值,为1.421亿hm²。（4）2001—2018年全国耕地年蒸散总量整体呈略微上升趋势,年际变化较大。五大粮食主产区中,长江中游及江淮地区年均蒸散量最大,四川盆地和黄淮海平原次之,三江平原和松嫩平原相对年均蒸散量最小。（5）在长江中游及江淮地区、四川盆地和黄淮海平原,蒸散发和干旱灾害具有较强的相关性;但在三江平原及松嫩平原,两者的相关性并不显著。结论 蒸散发作为大尺度可观测量在部分地区可以较好的反演干旱特征,研究中国不同下垫面蒸散发变化规律同时辅助其他变量,或许能为农业干旱监测预警进而估测粮食产量提供新的思路和方法。     

基于DPSIR-TOPSIS模型的耕地资源环境承载力分析以安徽省颍上县为例

目的 通过测算县域尺度耕地资源环境承载力,为耕地数量、质量与生态“三位一体”保护提供参考,为农业绿色高质量发展提供支撑。方法 文章根据DPSIR模型构建安徽省颍上县耕地资源环境承载力的评价指标体系,并采用改进的TOPSIS方法与障碍度模型,测算了2010—2019年安徽省颍上县耕地资源环境承载力指数并识别了制约当地资源环境承载力的障碍因子。结果 （1）2010—2019年从承载力指数看,颍上县耕地资源环境承载力总体呈现出“波浪式”上升的态势。其中,2010—2013年耕地资源环境承载力指数0.36下降至0.33;2014—2019年耕地资源承载力指数从2014年0.41上升至2019年0.70,承载力水平实现了从中级向良好的转变。（2）从障碍因子看,影响耕地资源环境承载力的关键因子由高标准农田比例、农药施用强度、土壤有机质平均值、免耕面积比转变为人均农业产值产出、人均耕地面积、土壤pH。结论 颍上县耕地资源环境承载力目前处于良好水平,同时在基础设施、体制机制等方面还有提升空间,为此提出以下政策建议：（1）加快高标准农田建设,提升耕地产能。（2）科学合理利用耕地,推进农业绿色发展。（3）加强土壤环境监测与治理,建立耕地保护的激励与管控机制。     

韩国乡村振兴地域制度及对我国的启示

目的 伴随着城镇化的快速发展、劳动力缺失、耕地效益低下等问题的出现,有效保护耕地和提高耕地利用率成为我国目前亟待解决的重要问题。方法 文章通过文献分析法和对比分析法,总结韩国乡村振兴地域制度建立的背景、主要框架和运行成效,提出对我国的启示。结果 为加强对农田的保护和利用,20世纪90年代韩国实施了农业振兴地域制度。该制度将农业振兴地域划分为农业振兴区和农业保护区,推行农业支援政策、实行人才培养和完善基础建设等一系列举措,在推进农业现代化、提高农民收入、保护耕地、保护农民权益等方面成效显著。结论 通过分析韩国农业振兴地域制度发展的经验,从健全法律体系、粮食主产区内划分现代农业重点区、实行粮食主产区的差异补贴政策、重视农业人才培养四个方面提出适合我国地区发展的农业振兴策略,以期为我国农业的持续发展提供参考。     

耕地质量禀赋、社会分工对农户化肥减量技术采纳行为的影响——基于鄂豫两省样本农户的实证

目的 促进农户采纳化肥减量技术是保障农产品安全、治理农业污染和推动农业绿色发展的重要举措,文章旨在探究耕地质量禀赋与社会分工对农户采纳化肥减量技术的影响及其内在逻辑。方法 基于湖北和河南两省700户农户的微观调研数据,利用Ordered Probit模型分析了耕地质量禀赋与社会分工对农户化肥减量技术采纳行为的影响。结果 （1）耕地质量禀赋对农户化肥减量技术采纳行为具有显著正向影响,耕地质量禀赋每增加一个单位,化肥减量技术采纳率将提高25%,土壤越肥沃,灌溉条件越便利,通机耕路的耕地,农户越会采纳化肥减量技术。（2）耕地质量禀赋越好,则农户更愿意参与横向分工,促进其采纳化肥减量技术,中介效应为0.062,且纵向分工能明显缓解质量禀赋较差耕地对农户化肥减量技术采纳的负向影响。（3）耕地质量禀赋对小农户采纳化肥减量技术具有显著正向影响,且社会分工增强了耕地质量禀赋对小农户化肥减量技术采纳行为的促进作用,而耕地质量禀赋对大农户化肥减量技术采纳行为没有显著影响。结论 因此,多渠道提升农户耕地条件,全方位推进农业社会分工,对不同规模农户采取差异化的激励和引导策略,均是推广化肥减量技术的有效途径。     

重庆市长寿区旱改水潜力评价与优化研究

目的 文章以重庆市长寿区为例,对其旱地改水田潜力进行测算,以期提高耕地质量,促进耕地内部结构调整和占补平衡,保障地区粮食安全和生态系统安全。方法 基于2010—2018年旱改水空间分布特征研究,构建旱改水适宜性评价模型,该模型涵盖地形条件、土壤条件、耕作条件3个评价维度,包括海拔高程、地形坡度、表层土壤质地等10个评价指标。然后利用模型评价旱改水整治潜 力,并识别整治的障碍因素,最后基于评价结果,提出旱改水的整治措施建议。结果 （1）2010—2018年长寿区旱地改水田整体集中度较高,主要分布在北部和中部地区,其中,密度最高的乡镇是海棠镇、云台镇和葛兰镇。（2）总的来说,重庆市长寿区旱地改水田整体适宜性不高,高度适宜和中度适宜改为水田的旱地面积分别为159.81hm²、8 115.64hm²,两者占全域总面积的25.22%,这些地块主要分布在区域中部、北部的石堰镇、葛兰镇、云台镇等乡镇;勉强适宜和不适宜改为水田的旱地占比为74.78%,这些地块限制性因素较多,难以改造为水田。结论 综上,未来长寿区可通过改造有效土层厚度低、地形坡度较陡、田块面积小、灌溉保证率低等障碍因素推动耕地旱改水工作。     

乡村多功能视角下耕地资源资产价值核算研究

目的 耕地资源具有经济、社会和生态三大功能,与乡村生产和生活密切相关。由于比较经济效益较低,耕地出现了面积减少、质量下降等现象,对耕地保护与粮食安全形成较大冲击。全面核算耕地资源资产价值,对于加强耕地资源保护、优化国土空间开发格局均具有重要意义。方法 文章从经济功能、社会功能和生态功能3个角度辨析了耕地资源内涵,提出了更全面的耕地资源价值指标体系,并以A县为例核算耕地资源的资产价值。结果 （1）乡村振兴背景下,耕地资源的社会服务价值更为突出;（2）缩小城乡收入差距的社会价值核算可以突显城乡协调发展中的问题;（3）生态损失是影响耕地资源可持续发展的重要因素,应在耕地资源价值核算中充分考虑。结论 有必要从加强保护耕地资源社会价值、推进农业核心技术攻关、提升农业供给效益、改善耕地肥力和减少耕地污染等方面提升耕地资源资产价值。     

Price transmission between products at different stages of manufacturing in forest industries

The theory of demand and supply implies a positive relationship, or “price transmission” between the prices of products at different stages of manufacturing. This relationship was investigated with quarterly prices of softwood stumpage in the US South, and national prices of forest products, from 1977 to 2002. All prices, net of inflation, were found to be nonstationary and there was no evidence of co-integration between prices. Vector autogressive models, augmented by Granger causality tests and multiplier analysis showed that there was a one-to-one permanent positive response of the southern sawtimber stumpage price to a permanent change in the national lumber price. There was also a one-third permanent positive response of the national paper price to a permanent change in the national pulp price. There was no relation between regional pulpwood prices and national pulp or paper prices. When price transmission was significant, the full adjustment took about 2 years.     

Application of an ecosystem function framework to perceptions of community woodlands

Owners, local residents, government, and conservation organisations can express divergent preferences in the development and management of local woodlands. The perceptions of these four groups were examined, in the context of three community woodlands in Eastern England, using an ecosystem function framework. In a pilot study, residents were able to allocate a relative importance to woodland ecosystem services which were then related to “regulation”, “habitat”, and “production” or “information” functions. However residents also placed importance on negative services or “dis-services” associated with the woodland ecosystem. Therefore a fifth category of “dis-services” was included in the main survey which included 84 local residents, three woodland owners, three government institutions, and six representatives from conservation groups. Each of the four groups placed greatest importance on services associated with habitat (16–39% of the total importance) and information (30–50%) functions suggesting, in this example, mutual interest in the use of woodlands as a habitat or recreational resource. By contrast a potential area of difference was the particularly high importance placed by one owner on dis-services such as fly tipping. In addition the woodland owners placed higher importance (10–20%), than local residents and conservation groups (7–9%), on the productive services of the wood. This suggests a need for communication when production-related operations affect recreation. The ecosystem function framework appears to be a useful approach for highlighting potential tensions and areas of mutual interest in the management of semi-natural ecosystems.     

The Effect of the Structural Adjustment Program on the Output,Prices and Exports of Major Agricultural Export Crops in Nigeria

The primary objective of this paper is to examine changes in the level of output, prices and exports of major export crops resulting from the Structural Adjustment Program (SAP) in Nigeria. THere two main sources of data: the Central Bank of Nigeria (CBN) through its annual reports, Economic and Financial Review, and the Nigerian Federal Office of Statistics (FOS) through its Trade Summaries. Although the SAP led to appreciable increases in output and producer prices, its effects on exports were insignificant. The implications of these for the implementation of the program are explored.     

土地学科的建设和发展——"土地学科发展规划研讨会"综述

中国土地科学学科发展已取得很大成就,表现为专业教育和人才培养成绩突出、初步形成学科体系、取得大批研究成果.而存在的问题主要是基础理论研究欠缺、独特的土地科学研究方法体系尚未形成、研究角度单一、学术交流质量不高和学科带头人的影响力不足.土地科学学科发展目前面临着巨大的机遇和挑战,应明确土地科学学科发展的基本思路、发展目标及2010-2020年的主要建设任务和保障措施.     

In Vino ‘No’ Veritas: impacts of fraud on wine imports in China

China is one of the largest wine importing countries in the world and is poised for continued import growth in the future. Increased wine purchases throughout China have given rise to persistent fraud where fake wines are packaged and sold with counterfeit contents and labels. For exporting countries like France, counterfeit wines displace market share, damage foreign brand reputation, and cause distrust in consumers who are aware of counterfeiting problems throughout the country. We examine the impact of fraudulent wine events (as measured by negative media reports) on Chinese wine demand differentiated by supplying country. We employ the Rotterdam demand system and a switching regression procedure to estimate import demand and compare results across different media variable specifications. Results consistently show that negative reports disproportionately affect French wine regardless of how the media variable is specified. This is not surprising because most fraudulent events involve French wine counterfeits.     

Evaluating Alternative Policy Responses to Higher World Food Prices: The Case of Increasing Rice Prices in Madagascar

Higher world food prices have led many developing countries to adopt policies to mitigate the impact on low-income households. This article sets out a partial equilibrium framework to evaluate the efficiency, distributional, and revenue implications of alternative policy responses. The model is applied to evaluate tariff reductions and targeted transfers in Madagascar. Although lowering tariffs generates substantial efficiency gains, these accrue mainly to the top half of the welfare distribution, and poor net sellers are actually worse off. Developing a system of targeted direct transfers to poor households is likely to be a substantially more cost-effective approach to poverty alleviation.     

An evaluation framework for earthquake-responsive land administration

In recent years earthquakes and their secondary hazards have claimed the largest number of lives of all large natural disasters. Some of the world’s most earthquake-prone zones are also areas of high population density. The impact is magnified by vulnerability factors including non-enforcement of building codes, knowledge gaps, urban poverty and poor governance capacity to manage and reduce earthquake risks. Poor security of land tenure and property rights increases the vulnerability of people and affects their ability to respond to natural disasters.Earthquake recovery and reconstruction provides very significant challenges for land agencies, with these challenges differing from one country to the next due to differences in the local context. Drawing on contrasting case studies in Haiti, Nepal and New Zealand this paper identifies the common post-earthquake land administration functions and challenges that may apply to many contexts. These lessons provide land agencies and other key stakeholders with a summary of the challenges an earthquake poses for land administration at different post-disaster stages. We also discuss the policy and regulatory, institutional, operational and preparedness lessons for land administration. From these lessons we propose a framework for evaluating the earthquake-responsiveness of a land administration system. This framework can be used by a land agency in an earthquake prone region, or where an earthquake has recently occurred, to assess what challenges to land administration might occur in the event of an earthquake, and the preparedness of their land administration system.     

Revealing different understandings of soil held by scientists and farmers in the context of soil protection and management

This paper aims to analyse and draw together results from similar studies in England, Switzerland and France which investigated farmers’ understanding of soil and compared it with that of scientists, researchers and advisors (collectively called scientists in this analysis). A range of methods were used across the three studies and different theoretical approaches, looking at forms of knowledge, local practice of knowledge production and conceptions of reality, were employed to explain the results. Despite the different contexts, methodologies and theoretical approaches in the three studies, the results reveal similar patterns of difference in farmer and scientist understanding of soil. In the English study, farmers demonstrate a ‘know-how’ form or intuitive working knowledge of soil while advisors rely on scientifically established forms of ‘know-why’ and seek to understand and explain soil processes. Similarly in the Swiss study farmers’ and scientists’ differing perceptions are directed and shaped by their respective aims, methods and context of work. In the French study, farmers and researchers are shown to have different conceptions of soil, they attribute different meaning to the same activities, and use different words and language to describe the same features. In all three studies understanding is shown to be cultural and contextual, as such an integrative theoretical framework is proposed.     

Transaction Cost Thresholds in International Rice Markets

Recent episodes of high and volatile prices for grains such as rice have raised concerns about their implications for hunger and poverty. We model price relationships between international rice prices and 221 domestic prices in 47 developing countries that import rice. We use a threshold vector error correction model that accounts for transaction costs of trade in spatial price transmission, and an improved regularised Bayesian threshold estimator for threshold models. Our results show that threshold values are higher after 2008 than before, which suggests that transaction costs in international rice trade have increased in recent years. Threshold values are highest for Latin American countries followed by African and Asian countries, and higher for retail than for wholesale prices. Since 2008, price transmission is slower in countries that responded to high and volatile prices with domestic market‐based interventions such as price controls and faster in countries that responded by lowering tariffs and by implementing production support measures.     

Agrarian Poverty,Nutrition and Economic Class – A Study of Gujarat,India

This paper analyses poverty and calorific undernourishment in the Indian state of Gujarat, where high and market‐led industrial growth has resulted in rapid economic improvement. The study is carried out through a combination of secondary and survey‐based data. We conclude that the neoliberal agenda of uncontrolled, outward‐looking growth has not resulted in significant reduction of poverty or malnourishment in rural areas. Furthermore, while land ownership is officially used as a proxy for wealth distribution, class position appears a better predictor of poverty status in the rural areas than landownership per se. At the policy level, there is a need to revive the agrarian economy and create new non‐agricultural assets, and the primary focus in the state must shift to the distribution of created assets rather than a single‐minded focus on growth.