Human Influence on Holocene Environmental Change in the Yangtze River Delta: A Combined Biomarker, 13C/12C, D/H, 14C, Pollen and Charcoal Approach

Biomarkers, 13C/12C, 14C, D/H, pollen and charcoal analysis are used to detect environmental change in the Yangtze delta during the Holocene. Particular attention is paid to identifying human influence in the record and also investigating the history of paddy rice agriculture in the delta region. Studies of this kind help to deepen understanding of human-environment relationships, and enable better assessment of the effects of current and future human activities on environmental change. 14C AMS dating of 8 pollen residues show the age of the sediment section to range between about 6000 and 1800 yrs B.P. Three pollen zones are recognized in the section. Pollen zone 1 (ca. 6000 -2600 yr B.P.) represents a period when forests and wetlands dominated the region. Pollen zone 2 (ca. 2600 – 2200 yr B.P.) is characterised by the dominance of herbaceous grassland and wetland environments. This type of environment persists through pollen zone 3 (ca. 2200-1800 yr B.P.) with additional signs of anthropogenic influence. Rice agriculture probably first became dominant in the region around 2600 yrs B.P., due to increased quantities of Cereal pollen and an increase in relative amounts of plant wax n-alkanes (C25-C31). This period is also characterised by a dominant methane cycle evident by the presence of 13C depleted 3β methyl-hopanes. Anomalously high relative amounts of a C20 highly branched isoprenoid (HBI) occur through zone 2. The origin of this compound is unknown, however it has been suggested to originate from epiphytic microalgae. High relative amounts of perylene, also of an unknown origin, occur in zone 1, and correlate with a period of higher lake levels and increased inundation in the delta.

Personnel

K. Grice, P. Atahan, J. Dodson, E. James

Funding

ARC

Collaborators

University of Western Australia, Brunel University ( UK)