江苏省耕地空间分布与变化研究

揭示耕地空间分布与变化规律,可为制定合理有效的耕地保护和区域发展政策提供依据.以往关于耕地空间分布与变化研究大多以单元间相互独立为假设条件,忽视单元之间相关性,这可能致使结果不能客观揭示耕地空间分布与变化特征.本文构建耕地指数与耕地变化指数,借助空间自相关与重心分析模型,对江苏省1980-2009年耕地空间分布与变化进行分析.研究结果表明:江苏省耕地空间分布与变化表现出严重不均衡,2009年耕地稀疏区与减少区主要分布在苏锡常,耕地集聚区、增加区和基本稳定区主要分布在苏中与苏北;耕地空间分布与变化具有空间自相关现象,2009年江苏耕地分布形成包括苏州、无锡市区在内的低—低相关区和沭阳、涟水在内的高—高相关区相对应的空间分布格局,2000-2009年耕地变化的低—低相关区包括苏州全部县(市),高—高相关区包括盐城中东部与宝应县、兴化市;相比1980年,2009年耕地分布重心向东北方偏移.     

重金属污染区农户休耕意愿的影响因素及其差异性分析——基于湖南省243个农户的问卷调查

理论分析农户休耕行为及其意愿决策机理的基础上,构建Probit模型,采用重金属污染区湖南省长沙市和株洲市部分休耕试点农户入户调研的243个样本,实证分析农户休耕意愿的影响因素及其差异性。研究表明:1)被调查者的年龄、耕地离家距离、耕地等级和对休耕政策认同程度对农户休耕意愿具有显著的正向影响;家庭劳动力人数占总人数比例、休耕前农业收入占总收入比例和休耕补偿期望偏差对农户休耕意愿具有显著的负向影响;2)不同年龄段、不同家庭劳动力占比、不同耕地离家距离和不同休耕政策认同程度限定下,影响农户休耕意愿的因素具有差异性。其中,对休耕政策认同限定下女性农户的休耕意愿比男性农户低,且农户年龄越大越愿意休耕;家庭劳动力人数占总人数比例在50%及以下的农户受教育程度与休耕意愿呈现正向影响;农户家庭特征和对休耕政策的认知是在大多数限定条件下影响农户休耕意愿的重要因素。重金属污染区农户休耕意愿的影响因素及其差异性分析结论将为制定政策调动农户休耕积极性和完善耕地休耕制度提供决策参考。     

An adaptive Mealy machine model for monitoring crop status

Variation in phenological stage is the major nonlinearity in monitoring,modeling and various estimations of agricultural systems. Indices are used as a common means of evaluating agricultural monitoring data from remote sensing and terrestrial observation systems,and many of these indices have linear characteristics. The analysis of and relationships between indices are dependent on the type of plant,but they are also highly variable with respect to its phenological stage. For this reason,variations in the phenological stage affect the performance of spatiotemporal crop status monitoring. We hereby propose an adaptive event-triggered model for monitoring crop status based on remote sensing data and terrestrial observations. In the proposed model,the estimation of phenological stage is a part of predicting crop status,and spatially distributed remote sensing parameters and temporal terrestrial monitoring data are used together as inputs in a state space system model. The temporal data are segmented with respect to the phenological stage-oriented timing of the spatial data,so instead of a generalized discrete state space model,we used logical states combined with analog inputs and adaptive trigger functions,as in the case of a Mealy machine model. This provides the necessary nonlinearity for the state transitions. The results showed that observation parameters have considerably greater significance in crop status monitoring with respect to conventional agricultural data fusion techniques.     

Confronting coexistence in the United States: organic agriculture, genetic engineering, and the case of Roundup Ready® alfalfa

In agriculture, the principle of coexistence refers to a condition where different primary production systems can exist in the vicinity of each other, and can be managed in such a way that they affect each other as little as possible. Coexistence policies aim to ensure that farmers are able to freely grow the crops they choose—be they genetically engineered (GE), non-GE conventional, or organic. In the United States (US), the issue of coexistence has very recently come into sharp relief with the introduction of Roundup Ready^® (RR) alfalfa, a landmark court decision in 2007 (Geertson v. Johanns), and subsequent governmental actions, including the first Environmental Impact Statement on a GE crop. By contrast, in 2003 the European Union (EU) created a policy to manage coexistence and to address economic harms that may be caused by contamination. We briefly review the EU framework as an instructive resource. This policy analysis then looks at the US organic industry and its standards with respect to GE before turning to the case of RR alfalfa. With a focus on the field trial stage and on environmental assessments prior to market approval, the case reveals numerous problems in the existing regulatory framework as it pertains to coexistence and prevention of contamination of organic products with GE material. The paper concludes with specific policy recommendations for creating a more robust coexistence policy in the US.     

Irony,tragedy, and temporality in agricultural systems,or, how values and systems are related

In the last decade the systems approach to agricultural research has begun to subsume the older reductionist approaches. However, proponents of the systems approach often accept without critical examination a number of features that were inherited from previously accepted approaches. In particular, supporters of the systems approach frequently ignore the ironies and tragedies that are a part of all human endeavors. They may also fail to consider that all actual systems are temporally and spatially bounded. By incorporating such features into a systems perspective, it becomes possible to consider them as involving the manipulation of things, the reconstruction of institutions, and the reformulation of policies in accordance with democratic goals and objectives as part of a single web of interrelationships.     

Conventionalization of the organic sesame network from Burkina Faso: shrinking into mainstream

This research examines the structure and development of the organic sesame network from Burkina Faso to explain the declining trend in organic sesame export. The paper addresses particularly the question whether the organic sesame network is structurally (re)shaped as a conventional mainstream market or whether it still presents a real alternative to conventional sesame production and trade. It is found that over the last decade organic sesame is increasingly incorporated into mainstream market channels. But contrary to the well-known case of conventionalization in California, where organic agriculture grew into mainstream agro-food arrangements, this study illustrates a case where organic sesame agriculture shrank into mainstream agro-food arrangements. The weak coherence between the production and marketing nodes in the organic sesame chain resulted in failures to vertically mediate information, balance power relationships in and across sesame chains, build trust, and limit price volatility and speculation, resulting in a shrinking organic sesame market. For developing a viable alternative to conventional sesame trading, relations between production and trading nodes in the organic networks need to be strengthened through public–private partnerships, combined with other public and legal reinforcement.     

A model for the spatial prediction of water status in vines (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) using high resolution ancillary information

This paper establishes and tests a model to extrapolate vine water status spatially across a vineyard block. The proposed spatial model extrapolates predawn leaf water potential (PLWP), measured at a reference location, to other unsampled locations using a linear combination of spatial ancillary information sources (AIS) and the reference measurement. In the model, the reference value accounts for temporal variability and the AIS accounts for spatial variation of vine water status, which enables extrapolation over the whole domain (vine fields in this case) at any time when a reference measurement is made. The spatial model was validated for two fields planted with Syrah and Mourvèdre during the seasons 2003–2004 and 2005–2006, respectively, in the south of France. The proposed spatial model significantly improved the prediction of vine water status, especially under conditions of high water restriction (PLWP < −0.4 MPa), compared with a non-spatial model. The model was robust to the choice of reference site. The results also highlighted that AIS pertaining to canopy growth are the most relevant variables for predicting PLWP under these experimental conditions. Preliminary results showed the potential to calibrate the model from a limited number of field measurements, making it a realistic option for adoption in commercial vineyards. The success of the spatial model in improving the quality of prediction of PLWP means it could be incorporated into a decision-support tool to improve irrigation management within a vineyard.     

A novel methodology for the monitoring of the agricultural production process based on wireless sensor networks

Precision agriculture is a field which provides one of the most suitable scenarios for the deployment of wireless sensor networks (WSNs). The particular characteristics of agricultural environments - which may vary significantly with location - make WSNs a key technology able to provide accurate knowledge to farmers. This knowledge represents a valuable resource because it enables real-time decision making with regard to issues such as establishing water saving policies while providing adequate irrigation and choosing the right time to harvest the fruit based on its maturity.This article proposes a methodology consisting of a set of well-defined phases that cover the complete life cycle of WSN applications for agricultural monitoring. We have studied different existing real-world scenarios where WSNs are being applied. Based on this study we have discovered that there exist significant commonalities but no methodology that specifies the best practices that should be used in the general, crop-independent case. The lack of a general methodology negatively impacts the amount of effort, development time, and cost of developing applications.     

基于WQI法的滴水湖及入湖河道水质研究

选取2018年8月至2019年7月间滴水湖及入湖河道区域水质调查数据及月平均降水量,按照水系特征及土地利用规律将研究范围分为五个区域。采用综合水质标识指数（WQI）法,评价分析水质时空分布规律;将该地区月平均降水量与氨氮和总氮进行比较分析。结果表明,滴水湖及入湖河道的水质具有空间上的差异性,外涟河、中涟河、内涟河、入湖口为“中等”,滴水湖区水质为“良好”,从外涟河到滴水湖区的水质呈现出逐渐变好的状态;和WQI显著相关的水质参数有总氮、氨氮等;降水对氨氮和总氮具有稀释作用。水质季节变化主要影响因子为水温和降水,空间变化主要影响因子为引水水源水质和人类活动。最后,根据该区域水质特征和影响因子,提出了生物治理法、改建雨水排放管道和加强重要指标监测等治理对策。     

湖南旅游经济空间网络结构特征研究

借用重力模型思想，基于社会网络方法，对湖南旅游经济空间网络进行密度、中心性、凝聚子群和核心-边缘等分析后发现，湖南旅游经济空间网络表现出结构松散、省会中心性明显、旅游经济空间的吸引范围正在逐步突破以及区域旅游一体化的市场基础好等特征。因而，重视旅游经济空间的均衡发展、发挥省会长沙的带动作用、注重跨界空间的合作、分步推进区域旅游一体化，可优化湖南旅游经济空间网络结构。     

Thermal evolution of plutons: a parameterized approach

A conservation-of-energy equation has been derived for the spatially averaged magma temperature in a spherical pluton undergoing simultaneous crystallization and both internal (magma) and external (hydrothermal fluid) thermal convection. The model accounts for the dependence of magma viscosity on crystallinity, temperature, and bulk composition; it includes latent heat effects and the effects of different initial water concentrations in the melt and quantitatively considers the role that large volumes of circulatory hydrothermal fluids play in dissipating heat. The nonlinear ordinary differential equation describing these processes has been solved for a variety of magma compositions, initial termperatures, initial crystallinities, volume ratios of hydrothermal fluid to magma, and pluton sizes. These calculations are graphically summarized in plots of the average magma temperature versus time after emplacement. Solidification times, defined as the time necessary for magma to cool from the initial emplacement temperature to the solidus temperature vary as R(1,3), where R is the pluton radius. The solidification time of a pluton with a radius of 1 kilometer is 5 x 10(4) years; for an otherwise identical pluton with a radius of 10 kilometers, the solidification time is approximately 10(6) years. The water content has a marked effect on the solidification time. A granodiorite pluton with a radius of 5 kilometers and either 0.5 or 4 percent (by weight) water cools in 3.3 x 10(5) or 5 x 10(4) years, respectively. Convection solidification times are usually but not always less than conduction cooling times.     

农业高质量发展的空间分异与影响因素 ——以广东省为例

农业高质量发展是乡村产业振兴的重要表征。广东省特色高效农业走在全国前列,以广东省为例量化评估农业高质量发展水平,可为各地诊断农业发展问题、监测农业高质量进展、支撑完善支持政策提供参考依据。本研究从高效化、绿色化和稳产化3方面构建了农业高质量发展评价模型,借助空间自相关分析方法、双变量空间关联性分析法分析了广东省农业高质量发展空间集聚特征与影响因素。研究发现,广东省农业高质量发展指数呈现“平原区>丘陵区>山地区”的特征,在空间上形成“平原区显著高高集聚、山地丘陵区显著低低集聚”的格局,高效化、绿色化和稳产化3个维度均呈现显著的正向集聚性,且空间集聚格局相似。农业高质量发展水平主要受到人均地区生产总值、高程等因素的影响,凸显农业高质量发展是一个因地制宜、循序渐进的过程,各地需立足本地资源禀赋、产业发展特色与地区经济发展水平综合施策。     

基于空间自相关构建树木生长模型

2004—2008年，在日本九州地区宫崎县田野天然次生林内设置的一块100 m×100 m固定标准地中，通过每木调查，测量了固定标准地内树木的种类、空间位置、生长等数据。为了便于理解，以固定标准地中优势树种蚊母树为主要研究对象，在考虑周边所有树木的影响的同时，利用贝叶斯统计方法分析了空间自相关及树木间的对称竞争、非对称竞争对树木生长过程的影响，并比较了忽略空间自相关的情况。结果表明:在构建研究对象树种的生长模型时，树木个体间的竞争是不可缺少的参数，尤其是个体间的对称竞争。在利用空间自相关参数建模时，最终模型的决定系数R2＝0.83；而忽略空间自相关参数的模型，其决定系数R2＝0.74。通过其他主要树种的分析也表明了导入空间自相关参数的优越性，因此可以认为，考虑空间自相关的随机效应模型能更精确地预测树木的生长。本研究所采用的空间自相关模型不仅可以利用树木个体的分布信息推测其生态学特征，还为树木生长模拟提供了理论与方法上的借鉴。      

吉林省农业支持与保护的宏观需求与供给能力分析

文中在吉林省农业支持与保护宏观层面的需求方和供给方都是中央政府和吉林省政府这一框架下,分析了吉林省农业支持与保护的宏观需求和供给能力.宏观需求主要体现在:建立稳固的粮食安全战略基地,切实维护国家粮食安全;稳定提高农民收入,保护农民的生产积极性;保证农产品加工业可靠的原料来源,依靠支柱产业加快地方经济发展;强化农业基础条件,稳定提高粮食综合生产能力.供给能力主要体现在:吉林省总体上已进入工业化中期阶段,具备了初步的"反哺"实力;我国已进入工业化中期的后半阶段,具备了基本的"反哺"实力;国家特殊的倾斜政策使吉林省农业支持与保护具有了可靠的宏观政策供给保障;对照WTO规则与我国的现实,农业支持与保护仍具有较大的"黄箱"政策利用空间.     

基于文本解码的中国“三农”政策演进研究

选取改革开放以来国家层面颁布的195份"三农"政策为样本，运用内容分析法和社会网络分析法来厘清"三农"政策演进的主要特征。结果表明：总体上，改革开放以来，"三农"政策呈现显著的阶段性特征，不同阶段的政策内容主题存在差异，呈现出单一聚焦向全要素统筹的总体趋势。具体看，政策发文数量呈现总体增长态势；政策发文主体呈现独立化向协作化发展趋势；政策内容趋向于精准化和全面化，且始终以农业发展和土地改革为重点，其中人才、科技及资金是乡村发展的关键。     

基于农户行为视角的农业支持保护补贴政策对耕地抛荒的潜在影响研究

20世纪80年代开始,我国出现大规模耕地抛荒,通过政策手段有效约束和引导农户行为,是解决耕地抛荒问题的关键。2016年原农业“三项补贴”政策改革为农业支持保护补贴政策,改革后的农业支持保护补贴政策涉及耕地数量保护、耕地适度规模经营等多个方面,可对耕地抛荒产生一定影响。为评价农业支持保护补贴政策对耕地抛荒的影响,本研究基于农户行为视角,构建了农户耕地抛荒的行为解释模型。模型包括（拟）退出农业生产的农户（农地转出方）和农地转入方两类行为主体,以及是否退出农业生产和耕地处置两个决策节点。基于该模型采用情景分析、逻辑推理等方法研究了农业支持保护补贴政策在不同决策节点对不同行为主体的影响,进而分析了政策实施可能对耕地抛荒产生的影响。研究发现,该政策的实施不会影响农户是否退出农业生产的决策,但会对耕地流转产生积极的影响。总体来看,农业支持保护补贴政策的实施有利于促进耕地保护,遏制耕地抛荒。     

Test of sampling methods to optimize the calibration of vine water status spatial models

Plant water status is one of the main factors affecting yield and quality in viticulture. Nevertheless, it is generally difficult to characterize it with enough precision for management purposes. In addition to its temporal variation, related to climate conditions, it has been shown that it is also spatially variable within the vineyard. In practical terms, this makes traditional reference measurements both too costly and time consuming to be affordable. In contrast, it has been shown that spatial variation of plant water status can be inferred from more accessible information, such as plant vigour in Mediterranean conditions. The main practical limitation for this approach is that the relationship between vigour measurements and plant water status is specific for each block and needs to be explicitly calibrated. Furthermore, a high number of measurements are usually required for this calibration. The objective of this work was to propose and test sampling methods to optimize the calibration of a specific spatial model of vine water status using the minimum number of measurements. Two model-based sampling methods commonly used in non-spatial modelling, Kennard and Stone (K&S) and Surface Response (SR) were considered, tested and discussed. Satisfactory results were obtained with both methods: with a sample size of 9 calibration sites, both sampling methods gave similar errors to the reference model (Root Mean Standard Error of Prediction, RMSEP = 0.1 MPa), which was calibrated with 49 sites. Taking into consideration the advantages and limitations of each method, K&S is considered to be better adapted for the case study presented. The proposed sampling approach could be extended to other spatial models used in precision agriculture in which ancillary variables can be used to explain most of the spatial variation for any agronomic information of interest.     

西藏民营经济发展问题及对策研究

分析了西藏民营经济发展的现状及特点,西藏民营经济呈现出快速增长趋势,成为财政税收的重要来源、社会就业的重要渠道,是繁荣城乡市场的主要力量。总结出制约西藏民营经济发展的主要因素,一是自然环境恶劣,生态资源压力大;二是民营经济发展水平低,基础薄弱,生产规模小;三是法律法规和优惠政策落实不到位,配套政策有待完善;四是金融支持不足,民营企业资金压力大;五是从业人员素质较低,民营经济管理水平不高。提出了加快西藏民营经济发展的对策建议:改善生态环境,转变经济发展方式;落实法律法规和优惠政策,完善配套政策;加大金融支持力度,促进民营经济发展;提高民营经济从业人员素质,培养企业家队伍。     

我国牛肉价格波动的门限及政策研究

为研究我国牛肉价格波动的非线性,挖掘其波动原因,利用两体制门限自回归模型对1995年6月—2012年12月牛肉价格同比指数序列进行分析,结果表明:我国牛肉价格同比指数是平稳的时间序列,其具有显著的非线性特征,估计的门限值为4.698,对应的同比价格指数为109.73%。通过构建13阶滞后模型,发现牛肉价格指数超过门限值后,牛肉价格受到的外部冲击大;低于门限值其波动主要源于自身,对后期影响更大。制定牛肉价格调控政策时,应将门限值作为政策出台的参考点,要注重市场的自我调控能力,适当适时介入市场。     

油气集输系统拓扑布局优化的混合遗传算法

给出了油气集输系统拓扑布局优化问题的数学模型，对其计算的复杂性进行了分析。根据模型的特点，采用了混合遗传算法进行求解，将局部搜索算法的快速性与遗传算法的全局收敛性有机地结合起来，有效避免了因初始值不同对优化结果造成的不利影响。实例计算表明，混合遗传算法优于传统的分级优化法。