古生态记录揭示的长江中下游太白湖生态系统稳态转换过程

Regime shifts revealed by paleoecological records in Lake Taibai's ecosystem in the middle and lower Yangtze River Basin during the last century

长江中下游浅水湖泊在过去百年内受到强烈的人类活动影响,生态系统状态发生显著的变化,服务功能逐渐丧失.为了更科学有效地管理浅水湖泊,当前迫切需要了解湖泊的生态系统转变过程.以长江中下游典型富营养化浅水湖泊太白湖为例,结合历史资料和监测数据,基于铅铯同位素重建年代序列,利用粒度、地化指标和沉积物中硅藻群落的时间序列数据,对太白湖过去百年间生态系统转变进行分析.基于T检验的STARS法检测硅藻群落的结果显示,有2个稳态转换分别发生在1950s末和1990s末.1950s末太白湖硅藻群落代表的生态系统状态发生了显著突变,这主要归因于由于建闸筑坝造成的水文条件和营养条件的改变;1990s期间的湖泊生态系统整体转变则是由长期营养输入和渔业活动加强导致的生态系统弹性损失引起的.讨论了不同阶段太白湖生态系统主要要素间反馈机制在水文条件改变和营养富集影响下的变化,加深了对人类活动干扰下太白湖生态系统结构变化过程的理解,为建立浅水湖泊系统动力学模型提供基础.

Shallow lakes in the middle and lower Yangtze River Basin are greatly influenced by human activities during the last century,subsequently ecological regime shifts have occured and some ecosystem services are degraded in some shallow lakes. In order to provide more scientific and efficient lake management,it is necessarily urgent to understand the transforming process of the lake ecosystems. In this study,we focus on a typical eutrophic shallow lake sited in the middle reach of Yangtze River Basin,namely Lake Taibai,and combine its related geochemistry proxies,grain size and fossil diatom assemblages from a sediment core dated in210 Pb and137Cs chronology based on paleolimnology with the basin's historical documents and monitoring data,to analyze specific regime shifts occurred in its ecosystem and changes of feedbacks inside driven by hydrodynamic changes and nutrient enrichement process. Results of diatom assemblages using STARS,a T-test based algorithm,revealed that at least two ecological shifts took place in the late 1950 s and 1990 s,respectively. The sudden shift in the late 1950 s is supposed to be influenced hydrological change caused by dam and sluice constructions in 1950 s and another shift in the late 1990 s should be a critical transition due to the alternation of cultured fish community and consistent nutrient enrichment,which led to gradual decrease in ecosystem resilience in Lake Taibai. Through analyzing the changes of feedbacks among main function groups in the ecosystem influenced by the change of hydrodynamics and euthrophication,we can have a deeper understand of the process of ecosystem structural changes disturbed by anthropogenic driversand lay the fundation for building a shallow lake ecosystem dynamic model in future researches.