性别对生物生长发育速率影响的研究

综述了自然界中性别在不同生长阶段对生物生长发育速率影响的研究进展。已有研究证明,许多生物的生长发育都有一个特点,即在生物生长初期,雌体的生长发育速率较快;而在生物生长发育后期,雄体的生长发育速率则较快。     

Rural livelihoods in the arid and semi-arid environments of Kenya: Sustainable alternatives and challenges

The improvement of the welfare of inhabitants of arid and semi-arid lands, either through the enhancement of existing livelihoods or the promotion of alternative ones, and their potential constraints are discussed. Alternative livelihoods are discussed under regenerative and extractive themes with respect to environmental stability. Regenerative (i.e., non-extractive) livelihoods include activities like apiculture, poultry keeping, pisciculture, silkworm production, drought tolerant cash cropping, horticulture, community wildlife tourism, processing of livestock and crop products, agro-forestry for tree products, and micro-enterprises in the informal sector. Examples of livelihoods that are extractive or potentially so include timber production, woodcarving, basketry, brick making, sand scooping, and charcoal making. Suggestions to improve these livelihoods in a sustainable manner are offered.Robinson K. Ngugi, PhD, is a Senior Lecturer in Biosystems Analysis whose specialty is animal resources in the rangelands. He has taught at the University of Nairobi, Department of Range Management for about 15 years and is widely published on various aspects of animal resources in arid and semi-arid lands.Dickson M. Nyariki, PhD, is an Associate Professor in Agricultural Economics whose specialty is Range Resource Economics. He has taught at the University of Nairobi, Department of Range Management for about 15 years and is widely published on various aspects of range resource use and development. Currently, he heads the University of Nairobis Department of Range Management.     

Monetary valuation of livelihoods for understanding the composition and complexity of rural households

There is, at present, little precise understanding of the relative contributions of the various income streams used by impoverished rural households in southern Africa. The impact of household profiles on overall income also is not well understood. There is, therefore, little consideration of these factors in national economic accounting. This paper is an attempt to reduce this gap in knowledge by reflecting on the relative contribution of agro-pastoralism, secondary woodland resources, and formal and informal cash income streams to households in the semi-arid rural village of Thorndale, Limpopo Province, South Africa. In the absence of jobs and confronted with high migrant labor, households with open access to natural resources derived more benefits from land-based livelihoods than cash income streams (i.e., 57.5 % vs. 42.5 %). Total livelihood income was valued at US$2887 per household per annum. A significant correlation between monetary values derived from crops and formal wages was established, and it was found that households with high cash incomes tended to invest more in crop production. Over 80 of households were male-headed. Of these heads of household, more than 60 were long-term migrants to urban areas, leaving household decision-making to the women. The low literacy rates of women have deprived them of paid jobs outside the area and, therefore, have increased their dependence on crops (62%) and secondary woodlands resources (60%). This was further reflected in the proportion of households in which females were the main contributors of cash income (9.7%), or joint contributors with men (24.4%). Various positive correlations were established between the number of women per household and the three land-based livelihoods. This implied that womens total control over such activities was mostly a result of the absence of men and not a typical phenomenon. In spite of this control, it was not positively reflected in the lives of majority of the women. Households differed in their participation in livelihood activities. Household size influenced the level of production and was positively correlated with the value of secondary woodland resources and crops. The study shows the interdependence of land-based livelihood sources and the impact of household features on production and consumption. Policies that focus on livelihood options need to recognize and accommodate associated household dynamics.Delali B. K. Dovie is a conservation biologist with interests in agricultural and natural resource economics and conservation, rural sociology, and global environmental change issues. He is currently a START/IGBP African Doctoral Fellow, and Honorary Research Fellow, School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, South Africa.E. T. F. Witkowski is an ecologist with expertise in eco-physiology, restoration and plant ecology, and ethnobotany. He is Professor and Director of the Restoration and Conservation Biology Research Group, University of the Witwatersrand, South Africa.Charlie M. Shackleton is an ecologist and Professor at the Department of Environmental Science, Rhodes University with many years of experience and good working knowledge of agro-ecological research, natural resources, plant population dynamics, and ethnobotany.     

Agriculture,livelihoods, and globalization: The analysis of new trajectories (and avoidance of just-so stories) of human-environment change and conservation

Globalization offers a mix of new trajectories for agriculture, livelihoods, resource use, and environmental conservation. The papers in this issue share elements that advance our understanding of these new trajectories. The shared elements suggest an approach that places stress on: (i) the common ground of theoretical concepts (local-global interactions), methodologies (case study design), and analytical frameworks (spatio-temporal emphasis); (ii) farm-level economic diversification and the dynamics of agricultural intensification-disintensification; (iii) the pervasive role of agricultural as well as environmental institutions, organizations, and governance issues; (iv) the ‹agency of nature’ that blends the roles of non-human organisms and the cultural and social practices of people both at the local scale and beyond; (v) the framing of sustainability initiatives and outcomes through the perspective of historical change; (vi)␣spatial environmental dynamics of the ‹new geographics of environmental conservation’ that impact agriculture, food production, and resource management; and (vii) successful and promising policies, projects, and developments mapping out possible spaces of hope for agricultural sustainability, aquitable development, and food security. The adoption and application of these elements is successful also in avoiding the tendency toward just-so accounts or overly simplified stories of agrarian and environment successes amid the often grim realities of globalization and its impacts. Karl Zimmerer is a geographer and environmental scientist researching and teaching on the topics of globalization and human-environment change (with emphasis on agriculture, conservation and rural livelihoods); the dynamics of agrobiodiversity in tropical mountains (currently focused on irrigation and the relations of new water resource management to agrobiodiversity change); and the development and experience of spatial-environmental models, environmental science, and conservation planning. Karl is the author of numerous articles and his books and monographs include four publications, most recently Globalization and New Geographies of Conservation (2006, University of Chicago). He is active in various organizations involved with agricultural, environmental, conservation, and globalization policies and also edits the Nature-Society section of the Annals of the Association of American Geographers.     

模型搭载的葡萄栽培管理决策专家系统开发

本文介绍了模型搭载的葡萄栽培管理决策专家系统的研究方法、开发平台、功能结构设计、专家知识获取、知识规则条理化、模型搭载以及智能推理举例等。     

土壤学发展历程、研究现状与展望

土壤学在农业可持续发展和生态环境建设中发挥了极其重要作用。随着现代科学技术和社会经济的快速发展,土壤学正在经历从传统向现代土壤学的转变。本文简单回顾了国际和中国土壤学的发展历程,分析了土壤学研究现状,指出了中国土壤学的研究特色和主要研究成果。同时,分析了当前土壤学研究领域所面临的问题和挑战,对其未来的发展趋势做出了展望,为土壤学的发展指明了研究方向。     

杂交粳稻发展的现状、问题与对策

回顾分析了杂交粳稻研究的历史、现状及存在的问题,并介绍了杂交粳稻的发展对策。     

木质护壁板产品设计研发的条件与方向

通过对环境状况、资源状况及市场前景进行分析,研究了木质护壁板产品设计研发的条件;通过进一步探究木质护壁板研发中可能遇到的问题点,明确了木质护壁板产品的研发方向。     

中国有机农业发展现状、问题和对策

从中国有机农业发展的现状出发,详尽记述了有机农业发展在政策、技术等方面面临的困境,提出了现阶段有机农业和有机食品发展的对策,即从政策扶持、市场开拓、理论研究、技术推广等方面的宏观策略。     

树立科学发展观 加快现代农业建设

现代农业是一个综合的、动态的、发展的概念。根据中国综合农业区划和现代农业发展状况,分别选择四种类型,即外向创汇型、高效集约型、节水旱作型、城郊都市型等基础好、代表性强的县(区)进行现代农业建设。     

石榴雌蕊分化,发育及其结构的研究

石榴具有2轮心皮,形成独特的合心皮雌蕊;子房中具有2种不同类型胎座:下部为中轴胎座,通常为3室,上部为侧膜胎座,5—10室(室数随位置而变化)。胚珠为具有两层珠被的、厚珠心型的倒生胚珠,珠心由周缘组织扩展而成。1个孢原细胞可直接发育或分裂形成1至多个大孢子母细胞,但只有1个正常发育。线型排列的四分体中,合点端的1个具有功能,其余3个退化。石榴胚囊的发育方式属蓼型,成熟胚囊中极核在受精前靠拢,但未发现愈合,3个反足细胞中一个退化较早。     

农民工旅游市场发展趋势与对策研究

介绍了农民工旅游市场现状,将影响农民工旅游市场发展的因素归纳为＂可支配收入＂、社保制度、闲暇时间、出游意愿,在此基础上探讨了农民工旅游市场的发展趋势,即表现在旅游市场规模扩大,＂新生代＂农民工将占据农民工旅游市场主体地位,旅游形式以一日游、自助游为主,旅游信息来源渠道日趋多样化4个方面。并从政府、旅游企业、用工单位等角度提出开发农民工旅游市场的相关策略。     

山西杂粮生产现状、前景与发展对策

在全面分析山西杂粮生产现状、杂粮生产优势、杂粮生产上存在的主要问题的基础上,提出发展山西杂粮生产的四点对策:一是进一步提高认识,加大扶持力度,整合杂粮力量;二是加强杂粮产前、产中、产后科研及推广工作力度;三是培育龙头企业,推进产业化经营;四是加强宣传,树立品牌。     

中国蔬菜产业发展现状分析、前景展望及对策研究

中国是世界第一蔬菜生产大国。文章通过从生产供给、消费需求、国际贸易等3个方面入手,深入分析当前我国蔬菜产业发展总体形势,对未来我国蔬菜产业发展前景进行研判,并最终从强化蔬菜供应链韧性、推动蔬菜产业链延伸、加快市场流通体系建设等方面提出促进我国蔬菜产业高质量发展的政策建议。     

图书馆知识女性职业生涯发展现状影响因素及策略

图书馆知识女性是高校人力资源中的重要组成部分。但与图书馆男性相比较,其职业生涯发展在业务素质、科研能力、职务职称方面都存在较大差距。究其原因,传统观念、生理和心理因素、图书馆职业性质影响了图书馆知识女性的职业发展。图书馆知识女性只有采取有效的策略突破自身局限,才能谋求职业生涯的最大发展。     

农民专业合作社的发展与管理——以贵州省罗甸县为例

为探索县域农民专业合作社的发展与管理,以贵州省罗甸县农民专业合作社为例,对农民专业合作社存在问题进行分析,并对农民专业合作社的发展与管理提出了建议。     

我国水果加工业发展现状、问题及对策

近年来,我国水果加工业规模不断扩大,加工工艺不断提高,质量标准体系初步建成,形成了初具规模的优势产业带,发展成以出口贸易为主的外向型产业,但同时也存在着水果加工原材料利用率不高、质量安全体系不健全、企业产业化进程慢、水果制品国际竞争力不强等问题。针对这些问题提出了提高产品综合利用率、健全质量安全体系、完善品牌建设、加大科技投入等对策建议,以促进我国水果加工业的进一步发展。     

光、温、水和红小豆生育及开花结荚的关系

采用分期播种法，分析了光、温、水等气候因素和红小豆生育期、生育结构及开花结荚的关系。结果表明，随着播期的推迟，全生育日数、播种至出苗日数、出苗至始花日数、始花至终花日数都逐渐缩短，日平均温度的升高是播种至出苗阶段缩短的主要原因；日平均温度升高，光照时数缩短，共同促进了出苗至始花日数的减少；光照时数缩短，使站花至终花日数逐渐缩短。5月29日红小豆单株花朵数、单株结荚数减少除了受播期各生育阶段缩短影响外，晚播花期降雨量减少是又一原因。     

福建省惠安县循环农业的发展思考

近年来,福建省惠安县循环农业不断发展壮大。阐述了惠安县循环农业发展的主要模式,分析了惠安县循环农业发展存在的主要问题,并提出了进一步发展惠安县循环农业的对策建议。