Dramatic biome changes in China through the Cenozoic Era: Modeling the combined effects of climate, CO2 concentration, and topography on long-term vegetation dynamics

Past vegetation patterns and dynamics reflect changes to the environment, climate, and human disturbance over time. As such, they comprise potential analogues for vegetation development under future climate change scenarios. Simulations of global and regional vegetation patterns in the present and future are well established; however, such simulations, especially over geological time-scales, have been remain relatively rare for China. Here, we used proxy-based reconstructions of paleoclimate, atmospheric CO₂ concentration, and topography (including uplift of the Tibetan Plateau (TP)) to drive an improved version of the global vegetation model BIOME4-Asia. Our aim was to simulate paleovegetation changes across China throughout the Cenozoic and to examine the combined effects of these factors on long-term vegetation dynamics. The simulations revealed dramatic shifts in biome distribution and coverage under varying climatic, CO₂, and elevational conditions. Catastrophic regime shifts occurred in response to sudden, pronounced environmental changes during several intervals. Forest biomes expanded northward and westward, with increased coverage, during warm and humid climates, high pCO₂, and lower TP elevation, especially between 66 Ma and 40 Ma. Conversely, forests retreated southward, grassland and desert biomes advanced eastward, and dry tundra expanded on the plateau during colder and drier climates, reduced pCO₂, and higher elevations, particularly between 2 Ma and 21 ka. During other periods, simulated biomes broadly resembled modern distributions. Overall, climate change, atmospheric CO₂ concentration, and TP uplift jointly shaped vegetation dynamics in China during the Cenozoic, consistent with model simulations, pollen and macrofossil evidence, and phylogenomic studies. Incorporating paleoclimate data from advanced climate model simulations, paleotopography and land-sea reconstructions, and paleosol properties will be critical for reducing modeling uncertainties in future work.