Late Quaternary carbon cycling responses to environmental change revealed by multi-proxy analyses of a sediment core from an upland lake in southwest China

摘要

Stable carbon isotope (delta C-13) values of organic matter in lacustrine sediments are commonly used to trace past changes in terrestrial and aquatic carbon cycles. Here we use a high-resolution, well-dated delta C-13 record from Lake Tengchongqinghai (TCQH) in southwestern China, together with other proxy indices, to reconstruct the paleolimnological history over the past 18.5 ka. Organic matter in the sediments of Lake TCQH is derived predominately from aquatic macrophytes. The lacustrine primary productivity is closely linked with lake-level changes affected by variations in the strength of the Asian summer monsoon and modified by evapotranspiration. Similar to lake sediments world-wide, a ca. -3 parts per thousand shift occurred in the delta C-13 values of Lake TCQH in response to the significant increase in atmospheric CO2 concentration during the last deglaciation. In the Holocene, the availability of dissolved CO2 in the lake water of Lake TCQH was determined by variations in hydraulic energy: low water turbulence creates a thick, stagnant boundary layer around aquatic plants, which will restrict the rate of CO2 diffusion and result in more positive delta C-13 values of aquatic plants. In contrast, significant water turbulence dramatically reduces the boundary layer thickness leading to more negative delta C-13 values of aquatic plants. (C) 2015 University of Washington. Published by Elsevier Inc. All rights reserved.