桂林会仙岩溶湿地环境变化沉积记录的初步研究

Environmental Changes Record Derived from Sediment Cores in Huixian Karst Wetlands,Guilin,China

为探讨亚热带地区岩溶湿地沉积环境的变化过程,在桂林会仙典型的岩溶湿地进行野外考察和连续柱状沉积岩芯采样,在寺湖和狮子潭钻取获得各长77 cm和57 cm的沉积岩芯,对其沉积年代学、营养盐元素、地球化学元素等方面进行高精度、高分辨率的样品分析,获得寺湖近450年来和狮子潭近200多年来的环境演化记录。结果表明:狮子潭经历了公元1810年以前的沼泽化过程而后又演化成湖泊沉积环境;寺湖在近450年来一直为湖相沉积,但经历了小冰期中的多次冷暖和干湿的气候波动;湿地沉积环境变化在过去主要受气候条件变化的制约,在气候的冷湿期有利于湿地的发育,而暖干时期则不利于湿地的发育。最近几十年气候的持续变暖和人类围垦活动的加剧对湿地环境变化的影响巨大。因此,要采取有力措施加大对湿地的保护力度。

Environmental change of the karst wetlands in the subtropical zone is an important scientific issue under the background of global change. For better understanding the processes of Karst wetland environmental changes with the climatic fluctuations and the human activities impact ,field investigation to Huixian Karst wetlands in Guilin City had been carried out and two sediment cores of 77 cm and 57 cm in length had been drilled separately in the Sihu Lake and the Shizitan Pond. Based on the analytical data of sediment chronology determined by ^137Cs and ^210Ph,and the content of TOC,TN,TP and the ratio of Mg/ Ca,Sr/Ca in the high resolution,environmental change history of the Sihu Lake in the past 450 years and the Shizitan Pond over the past 200 years has been discussed. The results showed that the cold and wet climatic condition would he propitious to wetland development and the warm and dry climatic condition would be disadvantageous for wetland development in the subtropical Karst areas. The Sihu Lake has maintained the lake sedimentary phase in the past 450 years but experienced shrinking and expanding processes. The Shizitan Pond had gone through a marsh deposit phase before 1810 AD and then changed into lake sedimentary phase due to the fluctuation of groundwater supply linked to precipitation. In the recent decades, the Huixian Karst wetlands has been in the shrink status as a result of both climate warming and human inning activities. Therefore, preservation measurements must be taken vigorously for this typical Karst wetlands.