试论长江流域自然环境的演化

THE ENVIRONMENTAL EVOLUTION OF THE YANGTZE RIVER VALLEY

依据青藏高原不断抬升及第四纪红色风化壳的不同性状,论证长江流域河流网系的台阶性特征,抬升的结果使高原东侧与北部高大山系足以阻隔西北寒流的冬季入侵,同时又强化了东南湿润气流的深入与阻滞于四川盆地西部及云贵高原北侧,因而使湿润亚热带生态环境得以深入上游地区。根据江南丘陵广泛分布的第四纪红色风化壳的特征,论证了整个地区均受到新构造运动抬升的影响,并在漫长的时期里处于湿润亚热带环境,成为孑遗陆生、水生物种得以长期存活的条件,同时使长江流域形成水热资源丰富、物种多样的河流网系。

The present paper deals with the environmental evolution of the Yangtze RiverValley based on the uplifting of the Qinghai-Xizang Plateau caused by Neotectonicmovement since Late Tertiary Era and extended to the whole Quaternary Era.Plateauof different elevations were formed.The plateau and high mountain ranges alongthe eastern and northern section of Sichuan Basin prevents the arid cold front fromthe northwest in winter,Otherwise,the invasion of the warm humid monsoon from thesoutheastern Pacifi coastal region into the western part of the basin and even up to thenorthern border of the Yunnan-Guizhou Plateau,thus the upper reaches of YangtzeRiver is in moist subtropical ecological environment.On the basis of the extensivedistribution of the Quaternary red weathering crust in the hilly region south of middlereaches of the River,the entire region has been affected by the continental uplifting,and has long been in the moist subtropical environment,hence the lasting survival ofcertain relic species.In the meantime,the Yangtze River Valley developed a networkof water courses under favorable hydrothermal regime as well as high diversity ofbiotic forms.