Evolution of the relative abundance of C4 plants on the Chinese Loess Plateau since the Last Glacial Maximum and its implications: C4 ABUNDANCE EVOLUTION ON CLP SINCE THE LGM

Understanding the distribution of C-3 and C-4 plants and its forcing mechanisms since the Last Glacial Maximum (LGM) is important for anticipating their possible response to future climate change. The spatiotemporal pattern of C-4 plant abundance on the Chinese Loess Plateau (CLP) is complex and the dominant causal factors are contentious. Here, we use delta C-13 records of organic matter in paleosols from the CLP to reconstruct changes in the representation of C-4 plants since the LGM. The results indicate that the relative abundance of C-4 plants increased after the LGM, reaching a maximum during 10-6 ka bp, and then decreased. Spatially, the representation of C-4 plants was characterized by increasing values from north-west to south-east. In addition, the smallest spatial difference (similar to 10%) in the representation of C-4 plants between the north-west and south-east parts of the CLP was during the LGM, and the largest difference (similar to 30%) was during the early Holocene. We combined our findings with output from the BIOME4 model to study the sensitivity of C-4 plants to changes in climate and atmospheric CO2 concentration. The results suggest that increasing temperature was the dominant factor driving C-4 plant expansion on the CLP since the LGM.