中国更新世环境巨变的孢粉植物群记录

PLEISTOCENE ENVIRONMENTAL MEGAEVOLUTION AS INDICATED BY THE SPOROPOLLEN FLORAS IN CHINA

通过对已有３８个剖面的孢粉时间序列分析，探讨了１．６ＭａＢＰ～０．８ＭａＢＰ的植被与环境巨变，划分出两个孢粉带及两个孢粉气候事件，提出该时段是更新世环境最恶劣的时期。该时期植被稀疏，北方一般以森林草原和草原为主，西北地区出现荒漠或荒漠草原，南方以森林及灌丛草原为主，表明当时气候冷干，降温幅度可达１５～１７℃，降水量减少３００～５００ｍｍ。这一环境变化使得亚热带树种再也没有返回华北及其以北地区，从而形成了现今植被分布的雏形。此后的植物群波动也发生了变革，波动幅度加大，波动频率增高。柴达木盆地云杉花粉的变化证实，此时青藏高原已上升到足以使植被状态发生转型的高度。

By an analysis of the sporopllen time sequences from samples of 38 sections, a discussion of the vegetational and environmental megaevolution in China during the time of 1 6MaBP^0.8MaBP was made,with the result that we have 2 zones of the sporopollen assemblages and 2 palynoclimate events. It is pointed out that it was the period of the worst environment in the pleistocene,during which vegetation was very sparse,with dominantly forest steppe and steppe in northern China,desert or desert steppe in northwestern China and forest and shrub steppe in southern China. It has been shown that the climate was then cold and dry,with a of 15~17℃ temperature drop and decrease En precipitation of 300~500mm. As a result no reappearance of subtropical plant has since occurrred in North China and further north,but an initial form of the present vegetation cover. There after there was a more frequent and larger flora fluctuation. The change of spruce pollen in Qaidam Basin shows that the Qinghai Tibetan Plateau had then been uplifted to a height that could cause a transformation of the vegetation.