Climatological Significance of Pollen Factors Revealed by Pollen-Climate Response Surface Functions in Dajiuhu, Shennongjia

Quantitative reconstructions of the mean July temperature and annual precipitation are performed based on pollen percentage contents from surface and stratum pollen samples, together with vertical meteorological observations across 700-2800 m in Dajiuhu, Shennongjia in Hubei Province of China. Canonical correspondence analysis and robust locally weighted regression of surface pollen samples are employed to investigate the relationship between plants and climate, and to build the seven pollen-climate response surface functions.Reconstructed results of the stable type assemblage exhibit the climate evolution since the Late-Glacial Period, including the Bálling-Allerád warm episode, Younger Dryas cold episode, Climatic Optimum, and cold events in 8 and 6.5 ka BP. The ranges of the mean July temperature and annual precipitation have been about 5°C and 300 mm since the Late-Glacial Period. Analysis of temperature and humidity reveals that Climatic Optimum with high temperature and precipitation occurred during early Holocene and former mid-Holocene, corresponding to the high resolution records in the low latitude region. The results indicate that the pollen-climate response surface functions are capable to valuate the comprehensive influence of temperature and precipitation on pollen content and can be used to reconstruct the past climate from pollen data.