- 期刊
- OpenAccess
A 5000-Year Pollen Record from Chitsai Lake, Central Taiwan
臺灣中部七彩湖過去五千年來之花粉紀錄
並列摘要
A 3.5m core taken from Chitsai Lake (altitude 2890m) of central Taiwan shows the vegetational and environmental changes in a Tsuga forest since 5000yr BP. During about 5300-4840yr BP(Zone 4), the Tsuga forest experienced a dear fluctuation toward a Tsuga-Cyclobalanopsis mixed forest. The high percentages of Cyclobalanopsis in the lower half of this zone (Subzone4b) indicate the last episode of the mid Holocene warm interval. Tsuga forest was well established in the later half of this zone. The extremely abundant spores as well as the finest sediments together indicate high lake level and moist climatic conditions. Between about 4840 and 3730 yr BP (Zone3), a warmer episode occurred in which Cyclobalanopsis increased slightly compared with Subzone 4a. Following this, during about 3730-2030yr BP (Zone 2), the relatively high percentages of Abies, Ericaceae and Tsuga as well as lower percentages of Alnus and Pinus indicate cooler but stable environmental conditions, Zone 1 represents vegetational changes during the last 2000 years. The increase in Cyclobalanopsis indicates warmer conditions than before. The remarkable decline of Tsuga and Ericaceae accompanying the increase in the secondary forest elements such as Alnus and Pinus may indicate a change in environment. The larger grain size of silt in Zone 1than in Zone 4, a higher erosion which may be due to stronger precipitation seasonality in a warmer climate. The upper 15cm shows rapid increase in secondary forest elements such as Pinus and Alnus. Whether it is related to the increasing atmosphere CO2 is worthy of further investigation.