晚更新世以来洛川黑木沟黄土地层中植物硅酸体研究及古植被演替

A STUDY ON PHYTOLITHS IN LOESS PROFILE AND PALEOENVIRONMENTAL EVOLUTION AT HEIMUGOU IN LUOCHUAN,SHAANXI PROVINCE SINCE LATE PLEISTOCENE

文中扼要介绍了植物硅酸体在古环境分析中的应用基础,详细研究了洛川黑木沟黄土剖面晚更新世以来植物硅酸体的组合特点、古植被及其演替规律,探讨了植物硅酸体分析在研究高分辨率气候事件及古气候空间格局中的意义。

The Loess Plateau is located in climatic sensitive area which recorded the whole processesof Quaternary climatic changes.It is very important to understand the paleovegetational suc-cessions in this area for the study of climatic event of high resolution and reconstruction ofpaleoclimatic and paleogeographic environment.However,as the spore-pollen is perseveredrarely,especially hard to identify the species,genus and even subfamily of herbaceous vegetation.It is very difficult to reconstruct the history of steppe plant and plant succession of the LoessPlateau,that is characterized by the dominance of herbaceous community.Study of phytolith (opal silica bodies) in the loess is a new component of paleovegeta-tional research,that fills up the shortage of pollen data in reconstruction of vegetational his-tory.As an effective indicator of paleoenvironmental analysis it has been used widely in paleo-pedology,ecology,archaeology and geology in previous studies.This paper is designed to study the phytiliths in the loess profile at Luochuan,ShaanxiProvince,in North China.21 samples have been taken from the Late Pleistocene loess and paleo-sol deposits to analyse the components of phytoliths,together with the study of distribution ofphytoliths in modern surface soils in China.More than 16 shapes of phytoliths have been given,the typical shapes identified in loess profile are square,rectangle,fan,short-point,smooth-rod,irregular,dumbbell and granular ones.Through the statistical analysis (R-mode and Q-modecorrelation analysis),different shapes of phytoliths are significantly corresponded to the climaticvariations,such as fan,square,rectangle shapes represented a warm and humid condition incommon case,while irregular and granular reflected a cool and dry environment.The result,obtained from the phytolith analysis in association with pollen research,has shown that theLuochuan area during Late Quaternary has undergone the following processes:dry steppe-desert steppe-siccideserta or desert steppe-steppe desert-dry steppe-open forest meadow (foreststeppe)-dry steppe or desert steppe-dry steppe-meadow steppe.The study of phytolith in the loess is only at the beginning,there will be more funda-mental researches to be done in the near future.However,this study no doubt will providesome important information for the reconstruction of paleovegetational history and paleocli-matic evolution.