Indian summer monsoon precipitation as the primary driver of C₄ vegetation dynamics in southwest China: isotopic evidence from a 28-kyr lacustrine record

Investigating the evolution of C₄ plants and their responses to climate change is critical for elucidating biosphere-climate interactions under anthropogenic global warming. However， insights into C₄ vegetation dynamics in the Indian summer monsoon （ISM）-dominated region of southwest China remain constrained by limited proxies and sparse availability of well-defined paleoenvironmental archives. This study presents a 28-kyr continuous compound-specific carbon and hydrogen isotope record derived from lacustrine sediments at Qionghai Lake， southwest China. Our reconstruction reveals a distinct decline in ISM precipitation before ～15 cal kyr BP， followed by a sustained increase during the last deglaciation. The abundance of C₄ plants exhibits a strong positive correlation with ISM precipitation intensity， demonstrating that hydroclimatic variability exerted significant control on C₄ vegetation expansion. Specifically， temperature was also a vital factor modulating plant responses， during pivotal climatic transitions such as the Last Glacial Maximum， Heinrich Stadial 1， and the Holocene Climatic Optimum. Comparative analysis with regional vegetation records further supports ISM-driven vegetation shifts in southwest China， with superimposed anthropogenic influences becoming evident in the late Holocene. These findings highlight the dominance of ISM precipitation in shaping Quaternary vegetation patterns， providing essential insights for predicting ecosystem resilience and informing adaptive agricultural strategies under future warming scenarios.