Climate conditions and relative abundance of C-3 and C-4 vegetation during the past 40 ka inferred from lake sediments in Wudalianchi, northeast China

摘要

Paleoclimate and paleovegetation changes over the last 40 cal ka were recorded by multiple variables in a sediment core from Qingshi, Wudalianchi City, northeast China. The history of vegetation types inferred from n-C-27/n-C-31 and average chain length of n-alkanes indicates the paleovegetation went through several distinct stages, consistent with pollen records from the study area. Compound-specific carbon isotope composition was also determined for C-27, C-29 and C-31 n-alkanes in the Qingshi core sediments. The relative abundance of C-3 and C-4 plants was calculated using a binary model and indicates that C-3 plants were the dominant input during the last glacial and Holocene. There were, however, shifts in the ratio of C-3 to C-4 vegetation abundance that correspond to changes in climate conditions. Generally, the long-term trend towards greater C-4 plant abundance from the last glacial to Holocene correlated with an increase in pCO(2), higher temperature, greater precipitation and more growing season precipitation. Our results suggest that temperature and seasonality of precipitation played a strong role in altering the relative abundance of C-3 and C-4 plants in the study area. These results provide information for predicting future vegetation changes in response to on-going global warming.