| Abstract: | This paper presents results of pollen analysis on sediments of core Cao 2 from Dianchi Lake. Four pollen zones are defined, namely zone I, which is further divided into four subzones, zone Ⅱ, zone Ⅲ and zone Ⅳ. Zone Ⅰ(ca. 47600–11800 yrs B. P.) is characterized by low land pollen sedimentation rates and constant presence of Abies pollen. In zone Ⅱ (ca. 11800–6900 yrs B. P.) broad-leaved tree pollen increases and Abies pollen gradually disappears. In zone Ⅲ (ca. 6900–3800 yrs B. P.) evergreen broad-leaved-tree pollen and total land pollen influx reach their maximum values while, Tsuga pollen decreases. Zone Ⅳ shows a great decreases in pollen influx of various pollen types and a increase in Monolete psilate spores. In the past 40000 years vegetation in this area trend changes from a dominantion of coniferous tree to an evergreen broad-leaved forest, co-existing or mixing deciduous broadleaved forest and coniferous forest. In the past 3800 years, due to climate changes and / or human activities, the vegetation cover in this area has been greatly reduced. The above vegetation changes indicate a climate change process from cool and humid, to warm and humid and finally to mild and dry. |
