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本文主要依据青藏高原众多断陷盆地湖相沉积中所取得的植物化石及孢粉学资料，间接证明中新世以后，青藏高原广大地区的亚热带常绿和落叶森林趋向减少，由桦木科、山毛榉科等北温带植物区系成分所组成的亚热带山地的落叶阔叶林显著增加。至上新世晚期，当在喜马拉雅山和横断山区生长着由高山栎组（ＱｕｅｒｃｕｓＳｅｃｔ．Ｂｒａｃｈｙｌｅｐｉｄｅｓ）和雪松（Ｃｅｄｒｕｓｄｅｏｄａｒａ）为主要组成的针叶阔叶混交林时，而青藏高原北缘毗邻柴达木盆地的昆仑山垭口地区，则分布着由云杉、冷杉、桦等组成的亚高山针叶林。进入距今２４０多万年的第四纪、伴随着全球性温度变动，引起森林和草原植被的多次交替，在早更新世间冰期时，昆仑山和唐古拉山区淡水湖沼广布，湖区仍有亚高山针叶林生长。至晚更新世，高原隆升高度接近现在时，森林面积退缩，植物区系组成和植被分区更加接近现代。值得注意的是，取自高原湖泊较高时间分辨率的孢粉学资料，揭示末次冰期间冰段、盛冰期、新仙女木期和大暖期植被和环境状况。
Based on the fossil and palynological data obtained from lacustrine sediments in many rift basin of the Qinghai-Tibet Plateau, this paper indirectly proves that the subtropical evergreen and deciduous forests tend to decrease in the vast areas of the Qinghai-Tibet Plateau after the Miocene. Branch and other north temperate flora composition of subtropical mountain deciduous broad-leaved forest increased significantly. In the Late Pliocene, when the coniferous and broad-leaved mixed forest composed mainly of Quercus Sect.Brachylepides and Cedrus deodara was grown in the Himalayas and Hengduan Mountains, the northern margin of the Qinghai-Tibet Plateau is adjacent to the Qaidam Basin Kunlun Pass area, the distribution of spruce, fir, birch and other components of the sub-alpine coniferous forest. Into the Quaternary of more than 2.4 million years ago, with the global temperature changes, causing vegetation and forest alternations of forests, early Pleistocene Ice Age, Kunlun Mountains and the Tanggula freshwater lakes and marshes are widely distributed, the lake is still sub Alpine coniferous forest grows. By the late Pleistocene, when the plateau uplifted to the present level, the forest area retreated, and the flora composition and vegetation division became closer to the present. It is noteworthy that the palynological data obtained from the higher temporal resolution of plateau lakes revealed the vegetation and environmental conditions during the last ice period, ice period, ice age, new fairy woody period, and warm season.