Soil microbial community analysis using denaturing gradient gel electrophoresis

The most biological diversity on this planet is probably harbored in soils. Understanding the diversity and function of the microbiological component of soil poses great challenges that are being overcome by the application of molecular biological approaches. This review covers one of many approaches being used: separation of polymerase chain reaction (PCR) amplicons using denaturing gradient gel electrophoresis (DGGE). Extraction of nucleic acids directly from soils allows the examination of a community without the limitation posed by cultivation. Polymerase chain reaction provides a means to increase the numbers of a target for its detection on gels. Using the rRNA genes as a target for PCR provides phylogenetic information on populations comprising communities. Fingerprints produced by this method have allowed spatial and temporal comparisons of soil communities within and between locations or among treatments. Numerous samples can be compared because of the rapid high throughput nature of this method. Scientists now have the means to begin addressing complex ecological questions about the spatial, temporal, and nutritional interactions faced by microbes in the soil environment.

The application of microwave radiation to analytical and environment chemistry

This review presents the latest advances in the application of microwave energy to analytical chemistry. The fundamental principles of microwave field interaction with the matter are presented and their significance for the chemist is discussed, followed by the basic principles of microwave equipment construction and operation. Examples of the techniques that utilized microwave energy for digestion, extraction, chemical reaction, preconcentration, and desorption of the analytical sample are presented. A separate section describes the examples of usage of microwave technology in catalysis, environmental, and nuclear chemistry and engineering.

黄土高原中部丘陵区生态农业结构模式及阶段目标

分析了黄土丘陵区农业生产现状和存在的主要问题 ,指出广种薄收习惯是导致土地利用不合理 ,植被遭到破坏 ,进而水土流失加剧和生态环境恶化 ,农业生产力降低的根源。该地区生态农业建设的核心是改变广种薄收习惯 ,治理水土流失 ,不断调整优化土地利用和产业结构。依据土地资源状况提出目前阶段 1 2 34的土地利用结构模式。认为在占总土地面积 2 0 %的基本农田和果园 ,只要实行集约化经营就可实现较高的经济效益 ,70 %的土地应为林草地。根据生态农业的基本原则和当前生产水平提出生态农业建设三个阶段的不同指标和适宜治理度 ,当前该地区主导产业的发展应以资源—结构—质量型模式为主

西部大开发中退耕还林(草)面临的挑战及其作用

根据中国西部森林的现状 ,采用生态学与地理学的方法 ,分析了因毁林开荒造成水土流失、洪涝灾害、沙尘风暴、干旱少雨、江河断流、物种减少等危害对国民经济发展所造成的影响 ,以及近几年所产生的一系列生态环境问题 .探讨了退耕还林 (草 )对我国的生态环境治理、西部持续发展、江河整治、国土整治综合措施运用、西部农民脱贫致富的作用 .