A 400,000 year record of vegetational and climatic changes from a volcanic basin, Leizhou Peninsula, southern China

Abstract

The Tianyang Lake in Leizhou Peninsula is an enclosed crater formed during the Early to Middle Pleistocene. Over 200 m of diatomaceous mud and clay were deposited in the last 400,000 years, providing a continuous Middle and Late Quaternary lacustrine sequence for paleoenvironmental studies. The pollen record spans the last four glacial–interglacial cycles equivalent to Oxygen Isotope Stages (OIS) 10 to 1. During most of the glacial phases, Fagaceous monsoon forest was replaced by altitudinal vegetation, indicating a regional landscape transformation on the peninsula. The montane forest reached down to the lowland by at least 600 m during the OIS 6 and 8 in a cool and relatively wet condition, with temperature estimated to be more than 4°C lower than present. A further lowering of the montane forest belts by about 800–1000 m occurred in the OIS 4–2, as implied by the appearance of many temperate elements. During the Last Glacial Maximum, this mixed forest subsequently gave way to the Poaceae grassland, a savanna vegetation type favored by drier and cooler climatic conditions. This drastic change implies a more significant drop in temperature and precipitation than the previous three glacial periods (OIS 10, 8 and 6). It is thus inferred that the weakening of summer monsoon was more significant towards the end of the Late Pleistocene particularly during the Last Glacial Maximum (LGM).