TRENDS IN THE URBANIZATION PROCESS     

CHRISTIAN WICHMANN MATTHIESSEN Ph. D. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):98-101

Matthiessen, Christian Wichmann: Trends in the urbanization process. The Copenhagen case. Geografisk Tidsskrift 80: 98–101. Copenhagen, June 1980.

Within the framework of the international comparative research project (Cost of Urban Growth) new trends in urban development have recently been observed. The object of this article is to discuss the trends and give impirical evidence on Danish data.  相似文献   

Deserts and Aeolian Desertification in China: Book review and some thoughts     

Raanan Katzir 《寒旱区科学》2013,5(6):0767-0768

Desertification is a global phenomenon that affects about two billion people. It occurs in arid zones where the annual precipitation is below 400 mm, partic- ularly in the marginal areas of the world＇s largest deserts. It is a result of water and wind erosion, over- grazing, global warm-ing, improper soil cultivation, and increased pressure ot population growth, and it causes degradation of soil and natural and agricultural vegetation. The direct result is less food for people and livestock, which influences pop- ulation and animal husbandry fluctuations. Despite ef- forts to combat and reduce desertification, the affected areas are annually increasing.  相似文献   

退耕还湿土壤生态恢复研究   总被引：1，自引：0，他引：1  

赵永强  张平究 《湿地科学与管理》2010,6(3):55-58

退耕还湿是湿地生态恢复的重要举措,土壤生态恢复是退耕后湿地生态系统恢复的关键。从湿地土壤概念、退耕后土壤物理化学性质、生物化学性质变化及土壤生态恢复进程等几个方面进行了综述,最后对退耕还湿后土壤生态恢复的进一步研究提出展望。  相似文献   

褐毛鲿人工繁育技术研究     

陈朴贤 《台湾海峡》2012,31(4):587-593

褐毛鲿（Megalonibea fusca）属石首鱼科（Sciaenidea）,毛鲿鱼属（Megalonibea）,是朱元鼎等（1963）命名的新种.其为近海暖温性底层大型鱼类,具有重要的经济价值.1998年福建省水产研究所开展褐毛鲿人工繁殖和育苗在国内首获成功,二批共培育出幼鱼6.667×105尾,其中第一批平均全长为32.55 mm和37.55 mm的幼鱼共8.680×104尾,第二批全长为24.0～35.0 mm的幼鱼共5.799×105尾.对1998年褐毛鲿室内人工催产、仔稚幼鱼的培育技术、仔稚幼鱼的食性和生长发育、生态习性,以及早期发育稚鱼阶段的适盐生存下限进行了分析.褐毛鲿适宜的产卵水温为23.0～26.0℃,盐度为29～32.催产激素以DOM剂量为3.5 mg/kg和LHRH-A3剂量为4.5μg/kg混合使用效果最好.仔、稚、幼鱼培育饵料依次为牡蛎幼虫、轮虫、卤虫、桡足类,在水温为24.5～29.5℃,盐度为18～28条件下培育,25d龄鱼苗全长为19.0～26.0 mm,80%完成变态进入幼鱼期,育苗成活率达25.3%.褐毛鲿稚幼鱼适盐范围为4～38,属于广盐性种类,可在海水和咸淡水中养殖.  相似文献   

The effect of cultivation method on erosion in agricultural catchments: integrating AHP in GIS environments   总被引：1，自引：0，他引：1       下载免费PDF全文

Tal Svoray  Roei Levi  Rami Zaidenberg  Beny Yaacoby 《地球表面变化过程与地形》2015,40(6):711-725

The cultivation method used in agricultural catchments can have a great effect on erosion processes; as such, determining the effects on form and degree is crucial. One commonly held hypothesis is that a shift to minimum tillage methods should reduce the rate of erosion. Here, we examine the effect of cultivation methods and environmental conditions on soil erosion risks in field crops and orchards in an agricultural catchment in northern Israel. The examination was conducted using AHP (analytic hierarchy process) and GIS (geographic information system)‐based computer simulations. Field validation of the simulations was conducted during the 2009–2010 winter season. The spatially explicit data on cultivation method, combined with environmental and climatic data, yielded an explanation of most of the variation in erosion risks in the catchment (kappa =0·93). Of the 10 criteria examined, the cultivation method and slope were the two variables with the greatest effect on increased soil erosion. Furthermore, soil loss risks were reduced substantially as a result of substituting conventional tillage with reduced tillage; substituting reduced tillage with conservation tillage; and changing the tillage direction to perpendicular to the direction of the slope. These results are reasonable in light of the modifications that mechanical tools cause in the soil structure, as observed in the penetration depth and the aggregate stability measurements used in this study. Despite the difficulty in collecting spatially explicit data on cultivation methods, we believe that it is of utmost importance to use such data to study erosion risks in agricultural catchments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

阳信黄冠梨种植气候条件分析   总被引：2，自引：0，他引：2  

周美燕  崔晓霞 《沙漠与绿洲气象(新疆气象)》2009,3(4):51-53

利用阳信县历史气象资料,对比阳信县气候条件与黄冠梨生长所需条件,统计分析种植黄冠梨有利和不利的气候条件,结果证明：阳信县气候条件适宜种植黄冠梨,对引进培育名优品种具有一定的指导意义。  相似文献   

法紫菜生物多样性及其栽培生物学基础     

王旭雷  马颖超  鲁晓萍  姜波  沈宗根  陆勤勤  沈颂东  卢山  何林文  牛建峰  汪文俊  夏邦美  茅云翔  陈昌生  谢潮添  骆其君  邵魁双  陈伟洲  王广策 《海洋科学》2017,41(2):125-135

综述了重要经济红藻法紫菜属物种多样性及其地理分布,修订了法紫菜属中文名称,回顾了紫菜生活史研究的历程,基本概括了法紫菜栽培生物学基础研究成果。根据文献报道及最新研究成果,认为紫菜属和法紫菜属共有138个物种,集中分布在北半球的温带、亚热带海域,其中我国是物种多样性较高的国家之一,其物种及变种数达到25个。法紫菜生活史的阐明对紫菜栽培产业的发展具有奠基性的作用,其中我国藻类学家曾呈奎和张德瑞在法紫菜生活史研究中作出了重要的贡献,提出了壳孢子的概念,被广泛接受并沿用至今。壳孢子采苗和丝状体培养技术是发展紫菜栽培业的重要基础,丝状体生长发育及壳孢子形成的分子机制将是未来法紫菜生物学研究的重点和难点。尽管根据已发表的相关文献大致梳理了法紫菜相关生物学基础研究的成果,但限于篇幅对栽培生产中相关技术的优化、完善与推广以及新品种培育等均未作介绍。  相似文献   

我国海洋渔业经济组织的演进与培育研究     

李嘉晓 《海洋科学》2017,41(6):119-125

我国海洋渔业从业主体类型多样,数量众多。对个体经济组织、合作经济组织、公司组织和企业战略联盟这4种海洋渔业主要经济组织进行了概述,分析了每种海洋渔业经济组织的演进,进而提出了顺应演进趋势对其进行培育的对策建议。  相似文献   

云南省怒江傈僳族自治州的人口问题     

周定一 《山地学报》1989,(2)

1964年以来,怒江傈僳族自治州人口增长与经济发展失调,由此而造成诸多社会-经济矛盾,严重妨碍着当地的发展。为改变现状,兹建议:完善和认真执行少数民族地区的计划生育政策,并由政府给予少量资助,在州内或向州外进行适量的人口迁移,以缓和人口压力,促进经济发展。  相似文献   

金湖县夹闵农业开发示范区优化种植规划研究     

冯定原  王彤 《南京气象学院学报》1996,19(4):464-469

从金湖县夹闵农业开发示范区的常年天然气候特点和现有耕地等自然资源出发，采用系统工程的思想观点和理论方法，按照不同的天气气候年型，分别构造了优化种植规划模型。计算结果表明，利用模型指民年度种植，既可保证全年粮食产量稳定在１．５万吨以上，又可使油料产量和经济净效益达最大。  相似文献