海南岛近2500a来盘星藻记录的周期性气候变化

湖泊沉积物中盘星藻含量变化可以反映湖泊水环境特征，对海南岛双池玛珥湖沉积物中盘星藻的研究发现，热带湖泊盘星藻种类以浮游类单角盘星藻为主，其含量在最近2500a以来相当丰富，而且其数量浓度的变化与湖水深度关系密切。频谱分析结果表明，近两千多年来盘星藻含量存在一个主要周期和一个次要周期，分别为421a和218a，前者与湛江湖光岩的结果可以对比，而后者则与206a的宇宙核素周期(^14C和^10Pe)十分接近。

CLIMATE CHANGES FOR THE LAST 2500 YEARS BASED ON PEDIASTRUM RECORD FROM HAINAN ISLAND

Lacustrine sediments can be considered as a good material recording the signals of lake level change. The microfossils in the lacustrine sediment are the important proxies for reconstructing the past climate. The results of pollen and algae analysis from up-wards 450 cm in the Shuangchi Maar Lake core of Hainan show that the content of Pediastrum occurred and increased rapidly with the rise in herbaceous pollen. The most abundant species discovered in the samples are P. simplex and P. duplex. Their percentage and concentration varied along the time series, which reflects the lake evolution and the periodic changes of the lake level. According to the spectral analysis based on the concentration data on the time-series, a dominant periodicity of 421 years in the last 2500 a was found, which is in accordance with the result from the Huguangyan Maar Lake. It is then suggested that the evidence of the 400-500 year periodicity may be a general climate effect (particularly precipitation) in tropical China. Another secondary periodicity of 218 years was also discovered that is similar to the documented 206-year period in records of cosmogenic nuclide production (carbon-14 and beryllium-10). The correlation with other studies in China shows that the decline of abundance of Pediastrum relates with the cooler and drier climate, whereas the rise in Pediastrum has the affiliation with warmer and wetter conditions. The recent study also times two events of relatively drier (1700-1300 a B.P. and 550-100 a B.P.) and two of wetter climate (2400-1800 a B.P. and 1200-600 a B.P.) since 2500 a B.P.