Reconstructing the 800,000-Year History of C4 Herbs on the Chinese Loess Plateau Using n-Alkane Carbon Isotopes
Document Type
Article
Keywords
Chinese Loess Plateau; C4 plants; Bothriochloa ischaemum; Pleistocene
Publisher
Quaternary Science Reviews
Rights Management
© 2024 Elsevier Ltd.
Abstract
C4 plants constitute a critical component in the modern ecosystem on the semi-arid Chinese Loess Plateau (CLP), and the changes in their abundances and distributions on geological time scales in response to climate factors such as temperature, precipitation, and atmospheric CO2 are a subject of intense investigation and debate. Reliable reconstruction of the percentage of C4 plants and a better understanding of its long-term variations in association with environmental and climatic changes are essential for interpretation of terrestrial ecosystem evolution. In this paper, we determine the carbon isotope and biomass characteristics of leaf wax on the CLP. We identify Bothriochloa ischaemum (L.) Keng as the dominant C4 grass, which accounts for ∼90% of the total C4 grass biomass and an average of 70% of the herbaceous community in the area. Using CO2 and precipitation corrected carbon isotope compositions from leaf wax n-alkanes as a proxy, we reconstruct a continuous history of C4 vegetation changes on the CLP during the Pleistocene. Our data indicate that a persistent grassland ecosystem existed on the tableland of the CLP, with C4 plants accounting for up to 40–53% during interglacial phases and 24–40% during glacial phases. Our findings suggest that temperature and precipitation, influenced by the East Asian monsoon, are key factors affecting the abundance of C4 vegetation in the region. The interactions with the monsoonal climate with warm-season precipitation in this grassland ecosystem throughout the past eight glacial cycles have important implications for the inhabitation of ancient humans in this region and underscore the challenges of vegetation restoration on the CLP under the projected warmer climate in the near future.
