Drought and fire suppression lead to rapid forest composition change in a forest-prairie ecotone

Altered fire regimes and increased drought can lead to major vegetation changes, especially in ecotones. A decrease in fire can lead to woody species encroachment in prairies and increasing forest stand density. The threat of global climate change raises questions about potential increases in the length, severity, and incidence of droughts substantially altering species composition. Re-measured upland forests in south-central North America's midcontinent forest-prairie ecotone exhibited major changes in woody species composition and structure over fifty years and successional trajectories appeared to favor invasive Juniperus virginiana L. over the previous dominant Quercus species. The objective of this study was to determine whether climate and fire exclusion affected the recruitment history of dominant woody species in these upland forests located near the xeric western edge of the eastern deciduous forest biome of North America. We removed cores and cross-sections from 992 J. virginiana, Quercus marilandica Münchh. and Q. stellata Wangenh. trees from eleven forest stands located across central and northwest Oklahoma, and determined their ages using standard dendrochronological methods. Recruitment of all species increased following a severe mid-20th century drought, but a rapid increase in J. virginiana recruitment and decrease in Quercus recruitment appeared to be linked to a decrease in fire. Future fire regime changes and increased drought due to global climate change could lead to widespread shifts from Quercus- to Juniperus- dominated forests and cause substantial changes to ecosystem services.     

应用竞争排斥法防制禽沙门氏菌感染

本文介绍了竞争排斥的概念,并概述了其在控制禽沙门氏菌感染中的效果、作用机理和实际应用等方面的研究进展,并讨论了这一方法的主要优点及其在家禽生产及人医上的潜在应用前景。     

对新形势下本土化农村社会资本研究的认识与反思

通过对我国本土化农村社会资本研究进行整体性的认识与反思,提出了系统研究和认识农村社会资本的基本思路和框架,从而为开发和利用农村各层类社会资本奠定了理论基础。     

对中国农民社会意识形态演变的分析

中国作为以农村人口为主的农业大国,农民是国家经济和政权的基础,农民素质的提高是经 济发展的前提,虽然长期以来“三农问题”始终羁绊着中国前行的脚步,但基于自中国实施改革开放 以来在政治、经济、科技、文化、教育等方面所取得的巨大进步,中国农民在社会意识形态领域发生了 极大的转变。因此,它将先从哲学、经济学、社会学等方面探究社会意识形态的形成、特点、及转变的 原因,得出社会意识形态的发展随思维的发展而发展的结论;然后将对改革开放以前中国农民社会 意识形态的特点进行概括性分析;最后将对自改革开放以来中国农民在教育观念、政治思想、法律思 想,经济意识四方面的演变过程进行较系统的研究。     

皖北贫困地区农村社会保障存在的问题及对策

构建和谐社会,统筹城乡经济社会发展的重要一环是建立新型农村社会保障体系,而皖北贫困地区农村社会保障更是其中薄弱的一环,其解决的好坏,将直接影响到新农村建设乃至整个社会的持续发展及和谐社会的构建。针对当今皖北贫困地区农村社会保障的现实背景、存在问题及已有研究理论进行仔细分析后,提出了解决这一问题的具体措施,主要包括:建立和完善农村社会救济制度、健全农村医疗保障制度等,以构建切实有效的农村社会保障模式。     

Experiences and perspectives of farmers from Upstate New York farmers' markets

Despite the growing popularityof farmers' markets (FMs) across the UnitedStates, the experiences and perspectives offarmers who sell at markets have received verylittle research attention. This study describesthe views of 18 farmers from Upstate New Yorkon the importance of FMs as part of theirlifestyle and livelihood, the challenges theyface selling at markets, and their conceptionsof ideal FMs. Through in-depth, semi-structuredinterviews, farmers expressed economic andsocial motivations for selling at FMs; socialbenefits from interacting with customers; andthe challenges they faced as small-scalefarmers and sellers, including extra-marketcompetition, uncooperative and problematicmarket vendors, rising farm input costs, andchanging consumer trends. Farmers alsodiscussed personal values associated withselling at FMs, such as pride in raising andmarketing one's own products, working togetherwith other farmer-vendors, and providingcustomers with honest information. Visions ofideal FMs were varied among farmers, but therewas general agreement that FMs should provide adiversity of products to attract customers andeducational opportunities for the public tolearn more about FMs and local produce. Theinterdependence of FM farmers was a majoremergent theme across interviews. Findingssuggested that market experiences of FMfarmers, including economic success, are notonly contingent on personal effort, but canalso be affected by the work of fellow vendors.Future research may look to further explore howFM farmers and other vendors interact ascooperative and competitive social and economicunits. At the community level, FM leadershipshould continue to focus on the experiences andperspectives of farmers and other marketvendors, in addition to identifying ways forenhancing cooperative FM enterprises.     

Rooted in grass: Challenging patterns of knowledge exchange as a means of fostering social change in a southeast Minnesota farm community

By convening a multidisciplinary team(the Monitoring Team) that included farmers,university and agency researchers, andnon-profit staff; a small group of farmers insoutheast Minnesota, U.S.A., bolstered thelegitimacy of the sustainable agriculturemovement. Through the experience of forming ateam and working with individuals who operatedwithin the mainstream knowledge paradigm,farmers gained validation of their knowledgeabout farming, while researchers came to valuealternative knowledge systems. In the contextof a socially embedded movement, farmers wereempowered by sharing their knowledge withresearchers, and ultimately contributed to thesustainable agriculture movement by challengingtraditional patterns of knowledge exchange.     

农业高新技术价值观念的评价

我国农业生产力的增长主要依靠农业高新技术。笔者对农业高新技术的本质特征进行了评价 ,指出农业高新技术是改造农业的工具和手段 ,其在应用过程中产生的积极作用和消极作用总是并存 ;同时也表明 ,农业高新技术是一种社会活动 ,受到各种社会条件的制约。并结合社会条件进一步分析了其价值取向 ,必须通过正确的决策和科学的管理才能最大限度地减弱和避免农业高新技术在实际应用中可能带来的消极影响。     

建立生态补偿机制的法律思考

生态补偿机制,就是以改善或恢复生态系统服务功能为目的,以经济手段为主,调整相关利益者(保护者、破坏者和受益者)利益分配关系的一种制度安排,生态补偿机制的实施有利于解决地区发展不平衡和社会不公平问题,法律是生态补偿机制有效实施的重要手段。从生态补偿机制的核心入手,分析了其实施法理基础和基本原则。     

吉林林区养老社会保障制度的改革和完善

指出了吉林林区养老保障制度存在的问题，论证了深入改革的必要性和改革目标，同时对建立养老保障制度中一些主要问题提出了解决的办法．