高山湖泊吉仁错枝角类古生态变化及其对气候环境的响应

Paleoecological change of cladoceran and the response to climatic environmental change from an alpine lake—Jiren Co

高山湖泊吉仁错位于川西高原树线以上,受现代冰川融水补给影响.通过吉仁错沉积钻孔^(210)Pb/^(137)Cs定年和沉积枝角类和多环境代用指标分析,结合主成分分析和冗余分析等方法,高分辨率重建了近200 a来吉仁错枝角类组合和环境变化的过程.结果表明,尽管过去200 a来吉仁错枝角类组合一直以沿岸种为主,但仍经历了3个明显的变化阶段.1850 AD后,枝角类组合中Alonella nana、Chydorus sphaericus和Pleuroxus sp.的增加、以及Alona rustica和Alona guttata丰度的下降指示了水温和水体pH值的上升.1900 AD后枝角类通量的增高并不同步于组合的变化,指示了湖泊营养开始增加,这种不一致的变化分别代表了大气氮沉降和区域气候变暖的影响结果.多指标综合分析得出,过去150 a来,气候变暖和大气污染沉降通过直接和间接作用(流域冰川融水过程和植被土壤过程),较深刻地影响了湖泊物理过程(水温升高和无冰期加长)、营养过程(氮、磷营养升高)和酸碱平衡过程(碱性增强),改变了湖泊生物的生长季节,并通过促进藻类发育,最终引起了湖泊枝角类群落组合的变化和生物量的增加.1945 AD前后吉仁错枝角类与藻类群落结构和湖泊环境的同步变化,响应于持续增温背景下多环境过程的相互作用.

Jiren Co is a small oligotrophic lake in West Sichuan plateau, located above＂the present tree-line and influenced by modern glacier meltwater input. Based on 21~pb/137Cs dating and multi-proxies （i.e., cladoceran, diatom and geochemical） from Jiren Co sediment core and using principal component analysis and redundancy analysis, this study analyzed the history of cladocer- an assemblage change during the past 200 years, and reconstructed the environmental change of Jiren Co. Although cladoeeran re- mains in Jiren Co was dominated by littoral species with significant changes over time, the core assemblages can divided into three distinct zones. After 1850 AD, the increase in abundance of Alonella nana, Chydorus sphaericus and Pleuroxus sp. and the decrease in Aloha rustica and Aloha guttata all indicate rising temperature and pH. After 1900 AD, cladoceran flux increased earlier than the change in abundance, which indicates the beginning of lake nutrition increases. This inconformity reflects the influence of climate warming and atmospheric nitrogen deposition, respectively. Multi-index analysis suggests that, over the past 150 years, climate warming and atmospheric deposition in the direcdy and indirectly effects （ice melt, vegetation and soil development） have affected the physical processes on the water temperature rise and prolonged ice-free period, nutrition processes on nitrogen and phosphorus increased, acid-base equilibrium processes on the increased alkalin. It changed the growing season and promoted the growth of al- gae, and finally affected on the assemblage and production of cladoceran. The synchronization change of cladoceran assemblage, al- gae and geochemistry proxies indicates a response of alpine lake to multi-environmental forcing under the background of continuous climate warming.