近300年来岱海流域气候干湿变化与人类活动的湖泊响应

根据岱海60cm柱状岩芯的磁化率、孢粉、粒度等环境指标的分析结果，对历史时期岱海气候干湿变化和人类活动的湖泊记录进行探讨，岱海湖泊沉积记录近300年来的气候干湿变化可划分七个阶段，与历史记载有较好的一致性；频率磁化率高值段对应气候偏湿阶段，低值对应气候偏干阶段，人类活动特别是人口增加和土地开垦，加剧流域水土流失，导致湖泊沉积物中细颗粒组分增加，频率磁化率升高；孢粉Ulmus的变化受流域人口增加的影响。频率磁化率和孢粉是反映岱海历史时期干湿变化和人类活动的重要环境指标。

Climatic Variation and Human Activities Recorded by Lake Sediment in the Catchment of Daihai Lake During the Past 300 Years

On the basis of studying magnetic susceptibility,spore pollen assemblages and partcle size of sediment from a 60cm core in Daihai Lake,historical climatic wt dry variation and human activities recorded by lake sediments in Daihai Lake are discussed.There were seven stages of climatic fluctuations in Daihai Lake from 1700AD recorded by the lake sediments,which coinciding with the historical document records of the area.It is suggested that high magnetic frequency dependent susceptibility indicate the period of wet climate and low magnetic frequency dependent susceptibility indicate the period of dry climate.Human activities especially the population rising and land reclaiming intensified the soil erosion and caused an increase of fine particle size and frequency dependent susceptibility.Changes of pollen content such as Ulmus was controlled by the increase of population.Magnetic frequency dependent susceptibility and pollen content of lake sediment are important environmental proxies which implicate the climatic wet dry transition and human activities in the catchemnt of Daihai Lake.