Changes in C3 and C4 plant abundances reflect climate changes from 41,000 to 10,000 yr ago in northern Leizhou Peninsula, South China

Abstract

Organic carbon stable isotopes (δ13Corg) have been widely used to estimate past C3 and C4 vegetation changes. As the relative abundance of C3 and C4 plants can normally be affected by multiple factors including atmospheric CO2 concentrations (ACC) and climatic conditions (e.g., temperature, aridity), the relative importance of these factors is still debated and may differ greatly in different regions. By using the δ13Corg records from a peat sequence in the tropical Leizhou Peninsula, South China, we estimate the past C3 and C4 plant abundances (CCPA) from 41,000cal BP to 10,000cal BP. The results indicate that lower δ13Corg values and thus more C3 plants generally occurred during Marine Isotope Stage 3 (MIS-3), whereas higher δ13Corg values and thus more C4 plants generally occurred during MIS-2. Moreover, several short positive excursions of δ13Corg records, indicating expansions of C4 plants also occurred, corresponding with the known YD and H1–H4 events in high latitudes. We conclude that the CCPA in northern Leizhou Peninsula is mainly controlled by precipitation, which in turn is associated with the East Asian summer monsoon (EASM) intensity, both on orbital time scales and suborbital time scales. The ACC may have slightly affected the long-term variation trend of CCPA on orbital time scales. It is likely that the temperature threshold, which is normally an important factor in high latitudes, may have less important influence on the CCPA in tropical south China. Our results provide the quantitative estimations of CCPA from the tropical Leizhou Peninsula, and more studies are necessary in low latitudes to examine possible connections between past vegetation changes and potential controlling factors on shorter timescales.