Paleohydrological changes in northeastern Taiwan over the past 2 ky inferred from biological proxies in the sediment record of a floodplain lake

Abstract

Taiwan is particularly sensitive to changes in monsoonal precipitation and to the frequency of typhoon-induced heavy precipitation events. Many parts of this mountainous subtropical island have high erosion rates that produce high sedimentation rates in lakes and offshore ocean basins, and evidence suggests that these rates have varied in the past. A high-resolution 2ky record of changes in sediment delivery to Dahu, a floodplain lake in northeastern Taiwan, that suggests changes in precipitation has been inferred from organic matter, pollen, and spores in a 12m sediment core and from the organic matter compositions of soil, catchment plants, and fluvial suspended sediment. From 0 to 1400AD, the lake experienced repeated flood events, principally resulting from overflows of the “old” Ilan River, one of tributaries of the Lanyang River, that were briefly interrupted ~1000AD by decreased precipitation and/or only localized rainfall. The record of heavy precipitation can be linked to the northward shift of the ITCZ. During the early Little Ice Age, 1400–1600AD, local erosion fluctuated in association with deforestation and farming, during which the ITCZ shifting varied as well. A decrease in precipitation since 1600AD is linked with the southward migration of the ITCZ.