Characteristics of the Later Hoocene Epoch Sporo-pollen Assemblage and Their Significance in Dabusu Lake,Qianan County,Jilin Province

According to the sporo-pollen analysis of the ten localities in Dabusu lake, it could be divided into two sporo-pollen assemblage zones from bottom to top: the lower series (1–2 bed) of Equisetum, lsoites sporo-pollen zone and upper series (3–6 bed) of Ranunculaceae, Chenopodiaceae, Aritemisia sporo-pollen zone. This paper deals also with the course that in the middle later period of the later Holocene Epoch the obvious change of paleogeographic environment is no less than twice in the area surounding Dabusu lake. As for the vegetation, the wet grassy marshland of temperate zone in which the pteridophyta Predominated turned towards meadow -steppe in which herbs predominated. While the wet climate turned towards arid climate and the fresh water lake turned towards salt lake.