Vegetation and climate variability in East Asia driven by low-latitude oceanic forcing during the middle to late Holocene

At centennial to millennial timescales, little is known of C3 and C4 plant productivity’s responses to past regional climate changes and the dominant forcing factors during the Holocene, although large-scale changes in glacial-interglacial periods have been attributed to changes in aridity, temperature, and CO2 concentration. We investigated the δ13C of TOC, C/N ratios, and pollen in samples from a wetland on Jeju Island, Korea. The bulk isotopic signal ranging from −17‰ to −29‰ was partitioned into C3 and C4 plant signals by using a binary mixing model and calculating separate organic carbon-accumulation rates for C3 and C4 plants (OCAR3 and OCAR4) during the last 6500 years. Pollen data indicated that the temperate deciduous broadleaved trees replaced grassland dominated by Artemisia, dry-tolerant grass, and further expanded in the maar. The long-term decreasing trend of Artemisia-dominated grassland was similar to those of δ13C values and OCAR4. The multi-centennial to millennial variability superimposed on the gradual increasing trend of OCAR3 was inversely correlated with those of the sea surface temperature (SST) in the western tropical Pacific (WTP) and El Niño-Southern Oscillation (ENSO) activity, suggesting that C3 plants have stronger sensitivity to regional climate change driven by oceanic forcing. Our data suggest that vegetation changes in a coastal area in East Asia were affected by monsoonal changes coupled with SST in WTP and ENSO activity. The vegetation change on Jeju Island varied quite differently from change in the westerly pathway, suggesting only a weak influence from high-latitude-driven atmospheric circulation changes. We conclude that centennial- to millennial-scale climate changes in coastal regions of East Asia during the mid- to late-Holocene may have been mainly controlled by low-latitudinal oceanic forcing, including forcing by SST and ENSO activity.

► Bulk isotopic signal was partitioned into C3 and C4 plant signals.
► Centennial to millennial vegetation change was correlated with those of SST and ENSO activity.
► Past climate change in East Asia was likely to be linked to the low-latitudinal oceanic forcing.