甘肃平凉地区约80万年以来的植被与气候变迁*

将该地约80万年以来的植被发展和气候变化历史划分为14个大的阶段.其中距今约80-78万年、20-14万年、10-1万年三个阶段的植被主要为荒漠草原,气候干冷;距今约78-64、55-46、14-10万年三个阶段植被主要为落叶阔林,气候温暖湿润;其它阶段的植被和气候处于上述二者之间.全新世早、中期,本区气候较现代温湿,晚期趋于温凉半干旱.

THE CHANGES OF VEGETATION AND CLIMATE IN PINGLIANG REGION,GANSU PROVINCE SINCE ABOUT 800 000 YR B.P.

In this paper,the stratigraphic sequence of the Ancun loess section in pingliang,Gansu province and the sporo-pollen assemblage of the samples taken from it were studied.The results indicate that many times of changes of vegetation and climate in pingliang area occurred during the past 800,000 yr B.P.The extent of vegetation changes is between deciduous broadleaved forest zone and desert steppe zone;and climatic changes are between warm-humid and cold-dry.The general treads of vegetation and dimatic changes since ca.800,000 yr B.P.may be divided into 14 large stages.There were three periods (i.e.around ca.800,000 yr B.P,200,000 to 140,000 yr B.P.,and 100,000 to 10,000 yr B.P.)in which climate was cold and dry,and vegetation was very sparse.The type of the vegetation was desert steppe consisting of Artemisia,Chenopodiaceae,Nitraria,Ephedra Tamariceae etc.Three periods(i.e.ca.780,000 to 640,000 yr B.P.,550,000 to 460,000 yr B.P.,and 140, 000 to 100,000 yr B.P.)were warm and humid.Vegetation was very thick and its type was deciduous broadleaved forest composed of Quercus,Rhus,Tilia,Juglans and Betula etc.For theperiods of ca.410,000 to 370,000 yr B.P.,330,000 to 300,000 yr B.P,and 250,000 to 200,000 yr B.P., the the type of vegetation was temperate needle-broadleaved mixed forest consisting of Quercus, Pinus,Betula and Juglans etc.,witha warm and subhumid climate.From about 640,000 to 550,000 yr B.P,460,000 to 410,000 yr B.P.,370,000 to 330,000 yr B.P.,and 300, 000 to 250,000 yr B.P.,the type of vegetation was dry steppe composed of Artemisia, Chenopodiaceae, Compositae and Gramineae etc.,and the climate was cool and dry.In the early and middle Holocene,the climate of this area was warmer and more humid than today.However, it tended to be mil-dcool and semiarid during the late Holocene.