Holocene environmental history inferred from pollen assemblages in the Huanghe (Yellow River) delta, China: climatic change and human impact

摘要

Palynological analyses of two boreholes from the Huanghe (Yellow River) delta, China, provide a palaeoenvironmental history of the last ca 12 kyr, particularly of millennial scale climatic changes and human impacts on the Huanghe drainage area for the last 4.5 kyr. In the Late Pleistocene (12 cal. kyr BP), fossil floras dominated by the xerophytic herb Artemisia reflect short-term climatic deterioration possibly Younger Dryas. Holocene 'hypsithermal' climatic conditions from 9.8 to 4.5 cal. kyr BP allowed monsoonal evergreen and broadleaved deciduous forests to thrive. From 4.5 to 1.3 cal. kyr BP diverse broadleaved deciduous trees and herbs flourished, although the climate was slightly cooler than previously, corresponding to a Neoglacial period elsewhere. However, minor warm events were recorded for 2.7-2.3 and 1.7-1.3 cal. kyr BP within this neoglacial period. A period of non-deposition occurred, from 1.3 to 0.21 cal. kyr BP because of the shift of the Huanghe to a different mouth and, following this period, the climate was cooler. Palaeoecological data indicate that human-induced vegetational changes occurred mainly at ca 4 and 1.3 cal. kyr BP as a result of deforestation and agricultural cultivation. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 47]