Search

To identify environmental causes for past changes in vegetation in subtropical East Asia, we present carbon isotope compositions of plant-wax n -alkanes and provide estimates of the C 4 -plant contribution across the past four glacial terminations and interglacials, based on cores recovered from the northern South China Sea. Our results show a comparable C 4 -plant contribution between the Last Glacial Maximum (LGM) and the Holocene. An increase of the C 4 -plant contribution by 15–20% is found for Terminations IV, II and I relative to subsequent interglacial peaks, coeval with an expansion of Cyperaceae and Poaceae. In contrast, Termination V reveals a lower C 4 -plant contribution than Marine Isotope Stage (MIS) 11c. The data exhibit a long-term trend, with a stepwise increase of the C 4 -plant contribution across interglacials MIS 11c, 9e, 7e and 1. We suggest that no substantial changes in humidity levels over glacial-interglacial cycles occurred facilitating a similar C 3 /C 4 -plant ratio for the LGM and the Holocene. Instead, deglacial sea-level rises caused an extensive development of floodplains and wetlands on the exposed continental shelf, providing habitats for the spread of C 4 sedges and grasses. The progressive subsidence of Chinese coastal areas and the broadening of the continental shelf over the late Quaternary explains the nearly absence of C 4 plant occurrence during Termination V and a gradual increase of the C 4 -plant contribution across interglacial peaks. Taken together, changes in coastal environments should be considered when interpreting marine-based vegetation reconstructions from subtropical Asia. • High-resolution plant-wax δ13C records for past four interglacials and glacial terminations. • C 4 -plant expansions on the exposed continent shelf occurred over glacial terminations. • Changes in coastal environments rather than climate cause alterations of vegetation composition. • Progressive broadening of the continental shelfs explains long-term vegetation changes. [ABSTRACT FROM AUTHOR]