中国城市化发展对粮食生产影响分析

1990年之后,我国粮食生产变动较大,同时我国城市化的两个主要方面——人口城市化和土地利用城市化继续迅速发展,分别表现为:粮食总产量波动很大,人均粮食产量呈减少趋势;人口城市化保持快速推进,导致农业劳动力数量减少、素质弱化;土地利用的城市化发展速度更快,造成耕地面积减少、质量不断降低。数据分析显示,我国目前粮食生产仍主要依靠劳动力和耕地两大基本要素的投入,因此城市化的上述发展特征,将对中国粮食生产造成不利影响。     

南宁市粮食生产影响因素分析

本文以南宁市为例,运用灰色关联度和生产函数,分析了1997-2003年粮食生产的影响因素及其贡献率。粮食产量灰色关联度分析作出关联因子排序:粮食单产>耕地面积>粮食作物播种面积>化肥施用量>有效灌溉面积>农村用电量>农业机械总动力>农药施用量,表明粮食单产、耕地面积与粮食作物播种面积对粮食总产的影响最大,从投入角度分析粮食总产与化肥施用量、有效灌溉面积关联度大;基于生产函数的贡献率分析表明:化肥施用量、农业科技进步、粮食播种面积、农业机械总动力、有效灌溉面积、农业劳动力对粮食增长的贡献率分别为40.08%、27.62%、12.12%、10.78%、8.91%、0.49%,说明7年来粮食增长主要依靠化肥投入、农业科技进步,农业劳动力对粮食产量增加作用微小。     

贵州省退耕还林地经济收益预测

退耕还林工程的可持续性,也就是该工程是否能达到预期的目标,关键要看农民是否能减弱或者摆脱对土地的依赖。而退耕还林地的未来收益将是退耕农户未来收入的组成部分,这将直接影响退耕还林后续政策的制定。因此,对退耕还林地未来收益的预测是后续政策研究的基础之一。该文在对贵州省进行实地调研的基础上,以马尾松林和核桃林分别作为生态林和经济林的代表,对其不同年份的净收益进行了预期,在此基础上,通过与退耕还林机会成本的比较,得出马尾松和核桃种植农户的收益情况。通过计算,得出对贵州省退耕还林的农户,至少是对还生态林的农户来说,现行补助年限过短的结论。     

新农村建设中的粮食价格问题

指出粮食价格问题是新农村建设中的一个重大问题,在强调粮食价格与新农村建设的关系、分析当前新农村建设中存在的粮食价格问题的基础上,着重探讨解决粮食价格问题、促进新农村建设的基本思路。     

粮食银行及其管理系统的研究与实现

针对粮食银行的经营模式和实际业务流程,设计并实现了基于web的粮食银行管理系统。经过对用户需求的分析,该系统主要有3类用户：储户个人、兑换点和粮食企业内部的应用部门。首先设计系统的总体框架和各模块的功能,然后以“兑换”业务为例,重点论述该业务信息系统的实现流程,认为其设计难点是数据库操作的实现。     

贵州生物质能源的发展与利用

生物质能源作为二十一世纪最具潜力的绿色能源。以其可再生和环保等优点而引起研究者的广泛注意。贵州拥有丰富的生物质能源资源,发展生物质能源具有明显优势。文章从沼气,燃料乙醇和生物柴油等三种典型生物质能源出发,论述其在我省发展的现状与潜力。     

粮食综合生产能力影响因素的系统分析及其政策建议

以系统科学视角从理论和实证角度将粮食综合生产能力分解为四个因子。通过主成分回归发现,水资源禀赋等自然生产力因子是影响粮食综合生产能力的基本因素;机械化率等技术生产力因子和耕作制度等管理生产力因子是主要促进因素;政策生产力因子影响不太显著,却是保障粮食综合生产能力的稳定因素。在目前生产条件下,稳定农业生产资料价格,改善农业基础条件,提高技术投入,选择良性生产模式,改革耕作制度,发展多熟制的间作套种,是今后提高粮食综合生产能力的主要方向。     

无偿转入土地对粮食生产效率的影响：福利还是负担？

在分析无偿转入土地对粮食生产效率影响的基础上,运用逆概率加权的方法,实证检验了其影响效果与作用机理。研究发现,与有偿转入土地相比,无偿转入土地是基于家庭社区伦理关系的非市场化行为。在解决了样本选择偏误的基础上,无偿转入土地整体上不利于粮食生产效率提升。其中的原因在于,流转租金缺位的无偿转入土地更容易弱化要素价格的信号功能与农户的生产改进意愿,进而使其在土地细碎化与农业长期投资上不能得到与有偿转入土地农户相同的改进。这一消极影响在户主年龄较小或文化程度较高、获得农业补贴较多或市场化水平较低、转入土地规模较小或期限不明确的农户群体中更为突出。长期来看,随着农村集体经济与新型农业经营主体的继续发展壮大,农村土地无偿流转的情况或将持续减少。但同时,也仍应当充分尊重土地无偿流转的现实选择与价值,立足于各地的具体情况来识别与谋划今后规模化经营的具体方向。     

Inequality and demographic response to short-term economic stress in North Orkney,Scotland, 1855–1910: Sector differences

We examine economic inequality and social differences in infant and child mortality, and fertility responses to food price changes in North Orkney, 1855–1910, using linked vital records. This small population featured a diverse occupational structure, limited land resources, and geographic isolation from mainland Scotland. Segments of Orkney’s non-agricultural working population were living so close to the margin of subsistence in normal years that an increase in food prices in bad years cost the lives of their children. Delayed childbearing, in addition to increased labour intensity, occupational diversification, and poor relief, failed to mitigate the negative effects of unfavourable prices in this group. While previous studies for Western Europe show a strong social gradient in mortality responses to food prices, and for Eastern Asia a strong household gradient, this study shows a strong sectoral gradient, indicating low standards of living for the non-agricultural working population well into the twentieth century.     

Mapping Invasive Species Risks with Stochastic Models: A Cross-Border United States-Canada Application for Sirex noctilio Fabricius

Nonindigenous species have caused significant impacts to North American forests despite past and present international phytosanitary efforts. Though broadly acknowledged, the risks of pest invasions are difficult to quantify as they involve interactions between many factors that operate across a range of spatial and temporal scales: the transmission of invading organisms via various pathways, their spread and establishment in new environments. Our study presents a stochastic simulation approach to quantify these risks and associated uncertainties through time in a unified fashion. We outline this approach with an example of a forest pest recently detected in North America, Sirex noctilio Fabricius. We simulate new potential entries of S. noctilio as a stochastic process, based on recent volumes of marine shipments of commodities from countries where S. noctilio is established, as well as the broad dynamics of foreign marine imports. The results are then linked with a spatial model that simulates the spread of S. noctilio within the geographical distribution of its hosts (pines) while incorporating existing knowledge about its behavior in North American landscapes. Through replications, this approach yields a spatial representation of S. noctilio risks and uncertainties in a single integrated product. The approach should also be appealing to decisionmakers, since it accounts for projected flows of commodities that may serve as conduits for pest entry. Our 30-year forecasts indicate high establishment probability in Ontario, Quebec, and the northeastern United States, but further southward expansion of S. noctilio is uncertain, ultimately depending on the impact of recent international treatment standards for wood packing materials.