|关键词: 花粉沉积|湖泊 植被源 流域降水 长江流量 百年过程 网湖
|100a pollen sequence and the sedimentary dynamics and environments in Lake Wanghu,middle reaches of the Yangtze River
YU Ge1, SHEN Huadong1,2
1.Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China;2.Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China
|This paper studied sedimentary pollen sequence for the last hundred years of Lake Wanghu, in the middle reaches of the Yangtze River, and analyzed the relationships of changes in pollen types and contents, sediment granularity, and climate-hydrology features during the past hundred years when the lake turned from an open water system into closed basin. Results showed that there were two major periods of lake-river connections and lake closing according to sediment and pollen features and to clustering analy-ais. Correlation analysis of time series from the pollen, granularity, catchment precipitation and river discharge, showed that they have significant linear relationships with 95% confidence interval. Major pollen types, including Pinus, ratio of evergreen tree Quercus to deciduous tree Quercus, sum of trees and shrubs, Cyperaceae, aquatics, upland herbs, and fern spores, showed 27%-40% synchronous changes with the time series of granularity and precipitation during the past 130 years, and 47%一57% synchronous changes with the time series of granularity and river discharge before 1960 when the lake naturally connected with the Yangtze River, suggesting pollen deposition was controlled sediments and catchment precipitation. We found different responses of pollen to sediments and precipitation: tree and shrub pollen with clay sediments responding to greater than 70th percentile precipitation changes, and aquatics and upland herds with silt sediments responding to less than 30th percentile precipitation changes.This study may provide scientific basis to reconstruct past environment changes by using sediment and pollen records, and to understand bio-sedimentology mechanical in the lake sediments.
|Key words: Pollen deposition lake sediment vegetation sources catchment precipitation discharge of the Yangtze River hundred-year processes Lake Wanghu