鄱阳湖地区土壤,植被光谱混合模型的研究   总被引：12，自引：1，他引：12  

张良培  童庆禧 《测绘学报》1997,26(1):72-76

本文针对鄱阳湖地区的土壤、植被的特点设计了一套非线性混合光谱模型、较好了地预测了实际的混合光谱，从预测精度上看，要优于传统的线性混合光谱模型。  相似文献   

末次盛冰期以来全球湿润状况的地质证据──全球古湖泊数据库及其湖水位变化的大尺度时空分析     

秦伯强  S.P.Harrison  于革  P.E.Tarasov  B.Damnati 《湖泊科学》1997,(3)

介绍了正在建设中的全球湖泊数据库的情况，以及该数据库的水位资料所反映的晚更新世末期以来全球湿润状况的变化。通过大尺度湖水位变化的时空分析，结果显示当今湖泊水位状态较历史时期而言，位于低纬干旱或半干旱地区的湖泊水位较低，而中纬及高纬湿润地区的湖泊水位较高。自末次冰盛期以来，北美大陆中南部地区湖泊水位自高至低，反映出该地区气候条件由湿变干，至早、中全新世达最干旱。而在非洲及南亚季风地区，冷期偏干，暖期偏湿。特别是在早、中全新世的温暖时期，为历史上最湿润时期。北半球中纬度地带的气候干湿变化与北半球冰盖的存在及其消融导致的西风带的南北摆动有关；而北半球季风区在早、中全新世出现的高潮面与北半球夏季辐射的增加有密切联系。  相似文献   

试论未来全球气候变化     

魏东岩 《化工矿产地质》1997,19(3):167-170

未来全球气候变化是人们关注的重大课题。从内蒙古盐湖近２０ｋａ气候演变的研究可知，地质时期和历史时期气候波动变化是有规律可循的。用已经了解的这种变化规律来予测未来气候变化是有价值的。研究表明，未来１ｋａ左右全球为暖期，之后将进入下一个冰期。  相似文献   

ON BIO-EFFECTS ON KARST LANDSCAPE IN JIUZHAIGOU CONSERVATION, SICHUAN PROVINCE, CHINA—WITH SPECIAL REFERENCE TO A MICROMORPHOLOFICAL APPROACH     

Zhang Jie Li Shengfeng Zhou Yinkang Du Jinkang Department of Geography  Nanjing University  Nanjing People''s Republic of China 《地理学报(英文版)》1997,(3)

1.ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｓｅａｒｃｈｏｎｂｉｏｋａｒｓｔｓｔｒｅｔｃｈｆｒｏｍｎｉｎｅｔｅｅｎｔｈｃｅｎｔｕｒｙ,ｙｅｔｏｎｌｙｒｅｃｅｎｔｌｙ,ｍｏｒｅｅｆｆｉｃｉｅｎｔａｎｄｓｙｓｔｅｍａｔｉｃｒｅｓｅａｒｃｈｈａｓｂｅｅｎｐｕｔｆｏｒｗａｒｄｗｉｔｈｔｈｅａｐｐｅａｒａｎｃｅｏｆｒｅｌａｔｅｄｓｐｅｃｉａｌｔｅｒｍｉｎｏｌｏｇｙａｎｄｄｅｔａｉｌｅｄｒｅｖｉｅｗｓ[3,11,30,3638],ａｎｄｉｔｓｅｅｍｓｔｈａｔｔｈｅｒｅｉｓｓｔｉｌｌｌａｃｋｏｆｂｉｏｋａｒｓｔｉｎａｌｐｉｎｅｅｎｖｉｒｏ…  相似文献   

The phytoplankton of some saline lakes in Central Asia     

Yoshiko Kawabata  Hiroyuki Nakahara  Yukio Katayama  Norio Ishida 《International Journal of Salt Lake Research》1997,6(1):5-16

The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes in Central Asia. They range from oligosaline to metasaline. The salinity of the Aral Sea has increased by more than 30 g L⁻¹ since widespread irrigation began in its catchment area. Few studies of the phytoplankton have been conducted on these lakes since extensive irrigation started. The investigation reported here compares the flora of phytoplankton in these saline lakes. In the Small Aral Sea, phytoplankton density gradually decreased with increasing electrical conductivity (EC) (∼ salinity), but there was no such relation in Lake Balkhash and Lake Kamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae were frequently observed in most areas of high EC value, and Cyanophyceae were most conspicuous in the area of medium and lower EC values. In Lake Balkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were also noticeable. Most Cyanophyceae in Aral Sea formed filaments with heterocysts. The distinct characteristic of the phytoplankton of the Lake Balkhash was that all dominant species form colonies covered with a gelatinous film. Siliceousplankton diversity gradually decreased with increasing EC values in the Aral Sea and Lake Balkhash.  相似文献   

Secondary ferrimagnetic minerals in Welsh soils: a comparison of mineral magnetic detection methods and implications for mineral formation   总被引：20，自引：0，他引：20  

J. A. Dearing  P. M. Bird  R. J. L. Dann  S. F. Benjamin 《Geophysical Journal International》1997,130(3):727-736

A study of mineral magnetic parameters was carried out on a Late Pleistocene and Holocene sedimentary sequence (of nearly 18 m) from Lake Bledowo (central Poland). Sediments of Lake Bledowo have already been analysed for bulk sediment mineralogy and biogenic materials. The mineral magnetic stratigraphy confirms the major changes in palaeo-environmental conditions that have been deduced from other methods. The most important mineral magnetic change results from the authigenetic formation of ferrimagnetic greigite, Fe₃S₄, during the beginning of lacustrine conditions (± 12 000 yr BP). Our data also indicate a detrital origin of overlying ferrimagnetic iron oxides. It is suggested that they originate from brown soils developed on the boulder clay constituting the west side of the lake shore. Variations of ferrimagnetic iron oxide size are related to the early diagenetic processes in the sediment. Larger particles are present in periods with early diagenesis of organic matter in anoxic conditions. This indicates the dissolution of fine magnetic particles by iron-oxide-reducing bacteria and results in homogeneous magnetic grain sizes, despite their origin from soils, characterized by a multimodal grain-size distribution.  相似文献   

Monitoring of rapid salt weathering in the central Namib Desert using limestone blocks     

A.S. Goudie  H.A. Viles  A.G. Parker 《Journal of Arid Environments》1997,37(4):581-598

Pre-weighed blocks of a Jurassic Limestone were exposed on the ground surface in the coastal Namib Desert for a period of 2 years. The environment is both salty and foggy. Some of the blocks suffered extensive disintegration, and laboratory analyses (including geochemistry, XRD and SEM) indicate that the weathered samples have a high halite (sodium chloride) content. Cycles of wetting and drying associated with the frequent fog events of the area cause cycles of halite crystallization. Rocks exposed at the surface absorb salts from the surrounding desert surface and then disintegrate, contributing to planation of the landscape.  相似文献   

察尔汗盐湖钾盐矿床与晶间卤水分异的关系     

徐少康 《盐湖研究》1996,4(2):64-69

通过钾盐矿床与晶间卤水分异特征及成因的分析对比，认为晶间卤水分异的过程也就是钾盐矿床形成的过程。胶结浸染状固体矿形成于晶间卤水分异初期的浓缩阶段，改造于分异后期的淡化阶段；晶间卤水矿和层状固体矿形成于淡化阶段。  相似文献   

硫酸盐渍土膨胀规律的综合影响因素的试验研究   总被引：9，自引：3，他引：9  

高江平  邓友生 《冰川冻土》1996,18(2):170-177

对含氯化钠硫酸盐渍土的膨胀规律作了综合影响因素的研究，首次提出了５因素盐胀率的计算公式，并得出了盐胀率的单因素和交互作用影响的规律；另外找出了某些因素的定量指标。  相似文献   

湖泊沉积物-水界面营养元素的生物地球化学作用和环境效应　Ⅰ.界面氮循环及其环境效应   总被引：7，自引：0，他引：7  

吴丰昌  万国江  黄荣贵 《矿物学报》1996,(4)

发生在沉积物-水界面的剧烈生物地球化学作用对沉积物和上覆水体具重要的环境效应，然而此方面研究很少。本文通过云贵高原四个湖泊湖水和孔隙水NH和NO剖面，沉积物柱芯不同结合态氮含量剖面分布，界面扩散通量，影响氮循环的因素及它们季节性变化规律等的对比研究，初步揭示了湖泊沉积物一水界面的氮循环及其环境效应。  相似文献