The combined effects of climate change and human disturbance has degraded lake ecosystems worldwide in recent times, but there are few studies that explore the relative impact of these factors over long timescales. In this paper, we use sedimentary pigment data to reveal variations in algal abundance and the lake ecological environment of a typical subalpine lake (Beilianchi Lake) in the southwestern Chinese Loess Plateau, to distinguish the relative effects of natural climate change and human disturbance over the past 5000 years. Our data show that between 5000 and 1400 cal yr BP, algal abundance exhibited a slow decline without obvious fluctuations, mainly driven by a gradually drying and cooling climate. After 1400 cal yr BP, algal abundance showed large and rapid fluctuations characterized by a pattern of a decline, then increase, and then decline again. During this period, human activities began to affect lake ecology and gradually overshadowed the role of climatic changes as the main driving factor. Enhanced human disturbances caused a rapid and synchronous decline in algal abundance due to increases in soil erosion and reductions in water transparency. Algal biomass levels recovered when the soil erosion intensity decreased during 800–500 cal yr BP corresponding to the period from Southern Song to Yuan Dynasties. Thereafter (during the period of Ming and Qing Dynasties), as human activities became further enhanced and the soil erosion intensity became very high, the lake ecosystem rapidly transitioned to a stable state of low algal growth. This indicates that the lake ecosystem may have had the capacity to recover from moderate external disturbances in the early stages of human activity, but the resilience of the lake ecosystem began to decrease under stronger human disturbances. Our findings provide important empirical evidence for evaluating the current state of lakes and for sound lake management in the future.

中文翻译：

---

1400年来人类活动导致黄土高原湖泊生态变迁

近年来，气候变化和人类干扰的综合影响导致全球湖泊生态系统退化，但很少有研究探索这些因素在长期尺度上的相对影响。本文利用沉积色素数据揭示了西南黄土高原典型亚高山湖泊（北连池）的藻类丰度和湖泊生态环境的变化，以区分自然气候变化和人类干扰对气候变化的相对影响。过去5000年。我们的数据显示，在5000-1400cal yr BP之间，藻类丰度呈现缓慢下降趋势，没有明显波动，这主要是由气候逐渐干燥和变冷所驱动。 1400cal yr BP之后，藻类丰度呈现出大而快速的波动，其特征是先下降，然后增加，然后再次下降。这一时期，人类活动开始影响湖泊生态，并逐渐掩盖气候变化作为主要驱动因素的作用。由于土壤侵蚀加剧和水体透明度降低，人类干扰的加剧导致藻类丰度迅速同步下降。在距今 800-500 年（对应于南宋至元代）期间，当土壤侵蚀强度降低时，藻类生物量水平恢复。此后（明清时期），随着人类活动进一步加强，水土流失强度极高，湖泊生态系统迅速过渡到低藻类生长的稳定状态。这表明，在人类活动初期，湖泊生态系统可能具有从适度的外部干扰中恢复的能力，但在较强的人类干扰下，湖泊生态系统的恢复能力开始下降。我们的研究结果为评估湖泊现状和未来良好的湖泊管理提供了重要的经验证据。