土壤退化的分类

土壤（地）退化虽自古有之，但土壤（地）退化的科学研究一直是比较薄弱的。联合国粮农组织1971年才编写了《土壤退化》一书，中国80年代才开始研究土壤（地）退化分类。所以目前还没有一个统一的土壤（地）退化分类体系，仅有一些研究结果，现列举有代表性的二种分述如下。

（一）联合国粮农组织采用的土壤退化分类体系

1971年联合国粮农组织在《土壤退化》一书中，将土壤遏化分为十大类：即侵蚀、盐碱、有机废料、传染性生物、工业无机废料、农药、放射性、重金属、肥料和洗涤剂。此外，后来又补充了旱涝障碍、土壤养分亏缺和耕地非农业占用三类。

（二）中国对土壤退化的分类

中国科学院南京土壤研究所借鉴了国外的分类，结合中国的实际，采用了二级分类。一级将中国土壤退化分为土壤侵蚀、土壤沙化、土壤盐化、土壤污染、土壤性质恶化和耕地的非农业占用等六大类，在这6级基础上进一步进行了二级分类。 一级 二级 A 土壤侵蚀 A1 水蚀 A2 冻融侵蚀 A3 重力侵蚀 B 土壤沙化 B1 悬移风蚀 B2 推移风蚀 C 土壤盐化 C1 盐渍化和次生盐渍化 C2 碱化 D 土壤污染 D1 无机物（包括重金属和盐碱类）污染 D2 农药污染 D3 有机废物（工业及生物废弃物中生物易降解有机毒物）污染 D4 化学肥料污染 D5 污泥、矿渣和粉煤灰污染 D6 放射性物质污染 D7 寄生虫、病原菌和病毒污染 E 土壤性质恶化 E1 土壤板结 E2 土壤潜育化和次生潜育化 E3 土壤酸化 E4 土壤养分亏缺 F 耕地的非农业占用

翻译：中国-全球环球基金干旱生态系统土地退化还有以下高分翻译,

中央项目执行办 Cental Poject Executive Office 国家林业局科技司 Science and Technology Depatment of National Foesty Bueau 财政部国际四项目四处 Depatment 4 of teasuy depatment's intenational fou poject 项目协调办 Poject hamony Office 资金处会计 the accountant of Capital Depatment 国家审计署外资司审计中心 the Audit cente of Foeign Capital Depatment of National Audit Bueau 中国-全球环球基金干旱生态系统土地退化 China-Gloal ound-the-wold fund Dought and iogeocenose and land degeneation。

英语作文 防止土地沙漠化

Nearly one-fifth of China's land has becomedesertified due to natural and human factors,forestry chiefs saidyesterday.A national survey reveals areas now classified as "sandy land" top1.74 million square kilometers-affecting 18.2 per cent of thecountry's total territory at the end of 1999.This represents a net increase of 17,180 square kilometers of sandyland--which is the transitional state of soil before it preventsany cultivation--in just five years,the State ForestryAdiministration(SFA) said.Distribution covered almost all of China's provinces, with 97 percent concentrated in 10 arid or semi-arid provinces and autonomousregions in the west.China's deserts witnessed a net increase of 52,000 squarekilometers between 1995-1999.Now six national programs have heen launched by the government tohalt the spread of deserts.rehabilitate ecosystems in semi-aridareas and prevent more dry land from turning into sandy soil ordesert-like areas.These projects are designed to cover more than 85 per cent ofChina's sandy land to form a framework for the country's long-termstrategy of controlling desertification.The National Afforestation Committee(NAC) yesterday honoredindividual and organization for their outstanding efforts incontrolling the spread of sandy land.Shi Guangyin and 100 other individuals plus 100 units engaged inafforestation were commended by forestry and personnel authoritiesat a ceremony in Beijing,for their decades of work on improvingland quality and preventing desertification.The event was held in the Great Hall of the People to commemoratethe eighth World Day to Combat Desertification and Drought.Honored as "the National Hero of Controlling Sandy Soil"--thehighest title of its kind in China.Shi,a farmer fromdesert-threat-ened Dingbian County in Northwest China's ShanxiProvince, has succeeded in bringing 13,000 hectares of sandy soilunder effective control and turning them into productive soilthrough planting trees and grasses."What Shi and the others did is a precious treasure of the Chinesenation," said SFA Director Zhou Shengxian."It should be followed by more people to support China'sintensified fight against expanding sandy land and worseningdesertification in the years ahead."Zhou said the country"has not fundamentally reversed the trend ofdeteriorating ecosysterms,with desertification worsening as droughtpersists and human activities,like overfarming andoveragazing,increase."。

英语六级作文题目及范文有哪些？

On maintaining trust保持信任 Future trends in computer science is one of the artificial intelligence,It is the research and artificial simulation of human thought and eventually be able to make a human like to think the same machine。

For human services and to help people solve problems。After all, people thought it was unique, there are feelings, there are a variety of character, this will be very difficult to achieve in the machine。

In fact, to do the same as the human thinking machine, the only one of the artificial intelligence, is by no means all。 Through the study of artificial intelligence, can resolve all kinds of scientific problems, and promote the development of other science, the artificial intelligence is the best!I believe that the science of artificial intelligence is waiting for humanity to explore it step by step the real connotation。

近两年英语六级作文范文

只有一篇 表格式的关于旅游的

2006年6月六级

1、近十年来某城市越来越多人选择出去旅游

2、出现这种现象的原因

3、这种现象可能产生的影响

表格：

1995 2000 2005

1万人 近4万 12万以上

范文：

From the table, we can see that in the past 10 years, the number of people in a given city who have gone traveling abroad has increased considerably. Especially in the recent 5 years, the figure has been more than tripled, surging from 40,000 to 120,000.

There are several reasons for the change. Firstly, with the development of economy, more and more people become better off. And their ability to finance their trip abroad is growing. Secondly, tourism has greatly developed over the decade. Travel agencies offer not only domestic packages but also travel specials abroad. In addition, individuals today are expected and encouraged to go outside to widen their horizon and to face the real world of globalization. In this way they hope to keep themselves informed of what is going on around the world.

From the changes reflected in the table, we can predict that the number of individuals going out of the country will boost. This encouragingly and inevitably facilitates the cultural exchange between ours and the rest of the world and this trend will be irreversible.

其他的没有了。

英语六级作文范文

我预测就业问题

College Students' Job Hunting

Nowadays, the employment of college students is becoming more and more of a problem. about a decade ago, university students could find satisfactory and enviable jobs after graduation, while the things are quite different at present. In addition, according to statistics, about 30% of graduate students can't find a job but stay at home after graduation。

Employment difficulty of college students is due to the following reasons. Among these, the increasing recruitment of colleges and universities plays a vital role. In addition, many colleges and universities fail to adapt their courses to the development of economy。

Considering the seriousness of unemployment of college students, I think it is high time that we took effective measures to solve the problem. Above all, college students should realize their own defects and further improve themselves to keep their competitive edge in society. Moreover, colleges or universities should provide more trainings and internship opportunities before the students enter the society. Besides, college students should hold a right attitude towards jobs and set their job expectations at a suitable level. only through these ways can the college students find a satisfactory job and have a brighter future。