An Early Pliocene lake and its surrounding vegetation in Zhejiang,East China

The palynomorph composition of an Early Pliocene assemblage from Du’ao Lake, Zhejiang Province, East China, including sporomorphs and algae, was analyzed to reconstruct the vegetation and climate around the lake, as well as the environmental conditions in the lake. A subtropical evergreen and deciduous broad-leaved mixed forest surrounding the lake is inferred from the pollen data. The composition of the green algae community indicates a clear, shallow (about 5–6 m deep), mesotrophic freshwater lake. The inferred pH was about 7.0–8.0 during the algae growing season. Applying the Coexistence Approach, the climatic conditions in Early Pliocene Du’ao were: (1) mean annual temperature ranged from 18.1 to 22.0°C, (2) difference in temperature between the coldest and warmest months ranged from 14.2 to 15.1°C, (3) mean temperature of the coldest month varied from 10.7 to 12.1°C, (4) mean temperature of the warmest month ranged from 23.5 to 25.4°C, (5) mean annual precipitation varied from about 994 to 1,255 mm, (6) minimum monthly precipitation ranged from about 9 to 11 mm, and (7) maximum monthly precipitation varied from approximately 219 to 245 mm. These values indicate that the Early Pliocene climate was subtropical.