Vegetation in subtropical formosa during the pleistocene glaciations and the holocene

Pollen analyses of three sections in central Taiwan (covering the Early Pleistocene and about the last 60,000 years) show several drastic vegetational changes with climatically (and, later, archaeologically) meaningful variations. A puzzling pollen assemblage, i.e., the boreal conifers (Abies, Picea, and Tsuga), and pine with pteridophytes, occurred in the Middle Waichiataoan stage (pollen zone W-2 possibly corresponding to the Praetiglian) that succeeded the early warm stage W-1. The Jih Tan core (745.5 m altitude) provides an important example of the Late Pleistocene vegetational history in the subtropics with an absolute chronological scale. The early Tali glacial stage (T-1) before ca. 60,000 B.P., is characterized by Symplocos, Tsuga chinensis, and Pinus, indicating that the temperature was 5.0–9.0°C cooler than today. The maximal Tali glacial stage (T-2), from some time subsequent to 60,000–50,000 B.P., contains predominantly the boreal conifers and pine, very low percentages of the temperate elements and plentiful aquatics (Trapa, Nuphar, and Persicaria). This was the coldest stage throughout the Late Pleistocene with a temperature decrease of 8.0–11.0°C, but nevertheless it permitted the growth of an eutrophic species of Trapa, in Jih-Yueh Tan. The last Tali glacial stage, from ca. 50,000 to 10,000 B.P., is dominated by the cool-temperate species (Cunninghamia konishii, Quercus, Ulmus, Zelkova, Juglans cathayensis, Ligustrum, and Salix). After the increase of temperature early in thi stage (between 45,000 and 40,000 B.P.), yet colder than the present, a short cooling phase came at around 35,000 B.P. An abundance of aquatic species and the formation of peat in the early Tali glacial time may indicate relatively dry summers, with perhaps a prevailing continental climate. In the Holocene,after about 10,000 B.P., the cool-temperate species were rapidly replaced by such subtropical and warm-temperate species as Mallotus paniculatus, Trema cf. orientalis, Liquidambar formosana, Castanopsis, Umbelliferae A type, and Cyathea. A sudden increase of chenopodiaceous and large-sized gras s pollen grains in both the Jih Tan Tashuiku Tan cores around 4,000 B.P., implies that agricultural activities have been intensified by new settlers from mainland China. A shrubby subtropical species (Mallotus) shows its peak during the Formosan hypsithermal interval.