过去1 300年南海东岛生态环境对气候变化的响应

东岛牛塘为目前在西沙群岛少见的淡水型湖泊,其中保存完好的粪土沉积物记录了距今1 300年来东岛生态环境演化历史.对DY4粪土沉积柱的研究结果表明,在1 400 AD前,东岛海鸟数量较多,牛塘湖岸周围植被生长较为繁盛,而在1 400~1 850 AD期间,东岛海鸟数量和植被生长都处于低谷.通过综合对比研究区、中国乃至北半球降雨量、温度变化记录,发现1 400 AD前岛屿生物量较高的时期对应于暖干的中世纪温暖期,而低生物量时期与凉湿的小冰期一致,证明南海热带孤立岛屿生态系统对区域乃至全球气候环境变化响应非常灵敏.

Eco-environment response to climate changes on Dongdao Island of South China Sea over the past 1 300 years

The Cattle Pond on the Dongdao Island is a rarely observed freshwater lake in Xisha Islands of South China Sea,in which the lacustrine sediments influenced by seabird droppings well record the changes of eco-environment on this island over the past 1 300 years.A sediment core named DY4 retrieved from the Cattle Pond was studied.The results show that before 1 400 AD there was a larger size of seabird population on the Dongdao Island,and relatively abundant vegetation grew around the Cattle Pond.In contrast,during the period of 1 400~1 850 AD,the seabird population and the vegetation abundance existed at comparatively low level.Compared with the historical records of precipitation and temperature changes in the study area,China and the Northern Hemisphere,we could clearly find that the period of higher biomass before 1 400 AD corresponds to Medieval Warm Period(MWP) characteristic of warm and dry climatic conditions,and that the period of lower biomass is consistent with the onset of the Little Ice Age with a cool and wet climate,which strongly implies that the isolated tropical island ecosystem in the South China Sea could sensitively respond to the regional and even global climate changes.