A 5000-Year Pollen Record From Chitsai Lake, Central Taiwan

Ping-Mei Liew,Shu-Yue Huang

doi:10.3319/tao.1994.5.3.411(pages)

Abstract

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.

Highlights

Over the last decade, there has been an increasing interest in understanding the global climatic changes
An alpine lake which is immune from anthropogenic influence would be an ideal site to provide proxy records for natural climatic changes
Based on the variation patterns of the main taxa, the following zones and subzones are delineated from the bottom upwards (Figure 2): 4.1Zone 4

Summary

Introduction

There has been an increasing interest in understanding the global climatic changes. An alpine lake which is immune from anthropogenic influence would be an ideal site to provide proxy records for natural climatic changes. High-resolution records for the past several thousand years are badly needed to differentiate between natural variations and those attributed to human impact. We report a high-resolution, detailed pollen record of the past 5000 years obtained from Chitsai Lake. The modem vegetation around this lake belongs to the Tsuga-Picea Zone of the mountain vegetation (2500-3100 m in altitude), but down core variation in pollen should reflect past changes resulting from possible vertical displacements of vegetation during the last 5000 years. Samples were taken at 3 cm interval to achieve a temporal resolution of approximately 30-50 years

Methods

Results

Conclusion