神农架大九湖15.753kaB.P.以来的孢粉记录和环境演变

A peat core with a depths of 297cm was obtained from the Dajiuhu Basin (31°29'27”N, 109°59'45”E, 1760m) of Shennongjia, Hubei Province, China. 10 dating data by AMS 14C method provide a high-resolution time scale and indicate that the core was deposited during the past 15753 years (calendar year). 137 pollen types were identified from 148 samples taken at 2cm intervals, among which trees and shrubs are dominant, 6 pollen zones were derived from bottom to top. In Zone Ⅰ, from 297cm to 203cm (15.753~11.280kaB. P.), pollen concentration is low but fluctuant on the one hand, on the other hand, percentages of conifers and aquatics are the highest in the profile, showings a frequent climate fluctuation during late-glacial period. According to the pollen percentage spectrum and concentration spectrum, it seems that the sub zone Ⅰ-1 (15.753~15.549kaB. P.), sub zone Ⅰ-3 (14.936~14.505kaB. P.) and sub zone Ⅰ-5 (12.655~11.280kaB. P.) correspond respectively the Oldest Dryas, the Older Dryas, and the Younger Dryas, while Ⅰ-3 (14.936~14.505kaB. P.) and Ⅰ-4 (14.505~12.655kaB. P.) the Boiling and the Allerod respectively. In Zone Ⅱ, from 203cm to 179cm (11.280~9. 218kaB. P.), pollen concentration and tree types increase, tree percentages increase, showing slow temperature rises. In Zone Ⅲ, from 179~143cm (9.218~7.530kaB. P.), pollen concentration decreases as a whole but the changes of different taxa vary heavily, i. e. , those of conifers and deciduous trees decrease, while that of evergreen trees increases gradually. The climate is warm and dry. Zone Ⅳ, from 143~113cm (7.530~4.051kaB. P.), represents the Holocene Optimum during which pollen concentration is the highest in the profile. Percentages of evergreen trees and deciduous trees are both high. Sub zone Ⅳ-1 shows fluctuated climate and sub zone Ⅳ-2 shows the best condition of water and heat during the Holocene. In Zone Ⅴ, from 113~33cm (4.051~0.911kaB. P.), pollen concentration decreases but the changes of different taxa vary acutely, among which percentage of evergreen trees decreases and that of deciduous trees increases. This zone implies a warm and dry climate during Late Holocene. In Zone Ⅵ, from 33~0cm (0.911~0kaB. P.), percentage of broadleaf trees, most of which are deciduous trees, is high; conifers increase obviously. It indicates that the climate during this period is cool and wet. Palynological data from the Dajiuhu Basin gives new evidence for paleoenvironmental reconstruction of the upper and middle reaches of the Changjiang River during the past 15753 years. The current primary research results show that the climate changes of this region not only are synchronous in a certain extent with other places, but also show local and regional characteristics.