全球变化知识资源中心

Numerous studies have focused on environmental changes and lacustrine ecological transitions in the modern industrial era. However, little is known about the processes of ecological transitions during early human disturbances. The current lake ecosystem state is the result of long-term integrated human influences on lakes. In this study, we present multi-proxy evidence of changes in the lacustrine environment, ecosystem, and human activities inferred from a sediment core collected from Beilianchi Lake in the southwestern Chinese Loess Plateau, to document the lacustrine ecological transitions with increasing human disturbances during the past 5000 years. Our data reveal the lacustrine ecosystem was quite stable with unchanging terrestrial versus aquatic sourced organic matter before major human disturbances (4400-1400 BP), although there was a decline in precipitation and a transition from tree-to herb-dominated vegetation. From 1400 to 300 BP, when early humans began to occupy and disturb the catchment, the lake experienced high-magnitude, centennial-to decadal-scale oscillations between aquatic and terrestrial sourced organic contributions. Thereafter, as human activities further increased, the lacustrine ecosystem finally stabilized at a state with terrestrial dominated organic matter. Our results suggest that the lake experienced large-magnitude ecological oscillations during the period of 1400 -300 BP, probably indicating the lake ecosystem retained the capability of recovery from the modest early human disturbances on the catchment. The recovery of the ecosystem to these external disturbances lasted hundreds of years with centennial to decadal scales oscillations. With further increased human influences since 300 BP, the lacustrine ecosystem probably finally shifted to another state largely deviating from its natural (climate-driven) background. (C) 2018 Elsevier Ltd. All rights reserved.