Tipping points can be defined as critical ecosystem thresholds that start self-enforced dynamics pushing systems into new stable states. Many lake ecosystems of arid Central Asia are sensitive to hydrological changes as they are located at the intersection of the influence of the dry Siberian Anticyclone and the relatively humid mid-latitude Westerlies, and their sediment records can be used to study past tipping points. We studied subfossil chironomid remains preserved in a ca. 6000-year-long sediment record from the Central Asian lake Son Kol (Central Kyrgyzstan) to reconstruct past ecosystem dynamics. Our results show abrupt transitions from a chironomid fauna dominated by macrophyte-associated, salinity-indicating taxa, to a vegetation-independent fauna, and subsequently to a macrophyte-associated, freshwater-indicating fauna. A comparison of the chironomid-based environmental reconstruction to other proxy indicators from the same record suggests a phase of increased Westerly strength starting about 4900 cal. yr BP. This increase led to enhanced precipitation and sediment fluxes into the lake, which in turn led to high turbidity levels and consequently to a macrophyte collapse causing abrupt changes in the chironomid fauna. At 4300 cal. yr BP, a weakening of the Westerlies in combination with higher lake levels led to lower turbidity and ultimately to the recovery of the macrophyte population and associated changes in the chironomid assemblage. These two sequences of events show how the occurrence of a gradual change in an external trigger (Westerlies) can trigger a cascade of within-lake processes (turbidity, macrophyte density) and may ultimately lead to an abrupt reorganization of the ecosystem (chironomid fauna), providing models for tipping points.

中文翻译：

---

生态系统在高山 Son Kol 湖（吉尔吉斯斯坦、中亚）的两个全新世中期临界点发生变化

临界点可以定义为关键的生态系统阈值，它开始推动系统进入新的稳定状态。中亚干旱地区的许多湖泊生态系统位于干燥的西伯利亚反气旋和相对湿润的中纬度西风带影响的交汇处，对水文变化很敏感，它们的沉积物记录可用于研究过去的临界点。我们研究了保存在一个约 100 米中的亚化石摇蚊残骸。来自中亚湖 Son Kol（吉尔吉斯斯坦中部）的长达 6000 年的沉积物记录，以重建过去的生态系统动态。我们的结果显示，从以大型植物相关的盐度指示类群为主的摇蚊类动物群突然转变为独立于植被的动物群，然后是大型植物相关的淡水指示动物群。基于摇蚊的环境重建与来自同一记录的其他代理指标的比较表明，西风强度从大约 4900 卡路里开始增加。年 BP。这种增加导致进入湖泊的降水和沉积物通量增加，进而导致高浊度水平，从而导致大型植物崩溃，导致摇蚊动物群发生突然变化。在 4300 卡路里。在 BP 年，西风带减弱与湖泊水位升高相结合导致浊度降低，并最终导致大型植物种群的恢复以及摇蚊组合的相关变化。这两个事件序列显示了外部触发（西风）的逐渐变化如何触发湖内过程（浊度、