在气候变暖和人类活动的共同影响下，全球众多湖泊的生态系统普遍呈退化趋势。研究过去增温变化对湖泊生态系统演化的影响有助于增进对当前湖泊生态退化机理的认识。项目选择黄土高原地区六盘山北联池为研究对象，从历史演变的角度，采用古湖沼学手段，结合现代监测，基于钻孔沉积物中支链甘油二烷基甘油四醚脂（brGDGTs）、色素和硅藻指标分析，重建过去5000年以来高分辨率的定量温度变化和湖泊生态演化历史。通过对比自然暖期（如仰韶暖期、秦汉暖期、隋唐暖期与中世纪暖期等）和现代暖期时段的湖泊生态记录，揭示湖泊生态系统对不同原因增温变化、不同幅度增温变化的响应过程与特征。在此基础上，结合流域人类活动数据，评估在过去千年以来人为干扰叠加过程中湖泊生态系统偏离自然演化轨迹的程度，及探讨从自然驱动到人与自然双重驱动下湖泊生态系统的响应机制。该研究将进一步加深对当前湖泊生态退化机理的认识、为应对未来生态变化提供科学依据。

Under the influences of the global warming and human activities, many lacustrine ecosystems show a general trend of degradation. Studying the effect of climatic changes on the evolution of lacustrine ecosystems over the past will be helpful to understand the driving mechanism of current ecological degradation. In this proposal, the PI will address this scientific issue based on paleolimnological analyses combined with modern monitoring at an alpine lake (Beilianchi Lake) in the southwestern Chinese Loess Plateau. First, the PI will reconstruct the regional quantitative temperature changes using brGDGTs (branched Glycerol Dialkyl Glycerol Tetraethers), and rebuild the lacustrine ecological changes by analyzing multiple biological proxies including pigment and diatoms. Then the PI will infer the responding processes and characteristics of the lake ecosystem to warming variations for different causes and different amplitudes, by comparing the paleoecological records between natural warm periods (e.g. Yangshao Warm Period, Qin and Han Warm Period, Sui and Tang Warm Period, and the Medieval Warm Period) and Modern Warm Period. Finally, the PI will assess the degree of lake ecosystem deviating from the natural evolution trajectory superimposed by human disturbance during the past millennium using various mathematical statistical methods, added with watershed human activity data, and further discuss the response mechanism of lake ecosystem driven from nature to human and nature. This proposed project will deepen our understanding about the mechanism of the current lake ecological degradation and provide a scientific basis for coping with future ecological change.