Regional heterogeneity and functional transitions of Holocene vegetation diversity in China

Understanding Holocene regional vegetation diversity and plant functional types is fundamental to predicting future ecological trajectories, yet such studies remain scarce. Here, we synthesized 255 pollen records, integrating multiple analytical methods and vegetation models to characterize vegetation succession patterns across five major regions in China. The Holocene vegetation diversity exhibited an asynchronous, inverted "U"-shaped trajectory (increase then decrease) constrained by regional climatic thresholds, with pivotal transitions occurring between ∼8000 and ∼4000 cal a BP. The abrupt cold event prior to 8200 cal a BP highlights the ecological buffering capacity of forested areas, whereas the drought event prior to 4200 cal a BP triggered irreversible ecological tipping points in steppe regions. Subsequently, dominant drivers shifted from climate to human activity after ∼4000–2000 cal a BP. Concurrently, woody plants expanded northward and westward during the early-mid Holocene, followed by widespread forest retreat in the late Holocene. Based on our findings, we anticipate that under future warming scenarios, vegetation in southern China may transition toward an optimal diversity state reminiscent of the Holocene Climatic Optimum, whereas vegetation dynamics in northern China will dependent on regional precipitation trends.