Stable carbon and oxygen isotopes of terra rossa in Guizhou Province of China and their relationship to climate and ecology

Abstract

This paper analyzed stable carbon and oxygen isotopic changes in organic matter (δ 13CSOM) and disseminated carbonate (δ 13CSC and δ 18OSC) in four terra rossa profiles in Gouzhou, southwestern China. The objectives were to understand more information about climate change in this area and to determine whether the isotope values of disseminated carbonate in terra rossa preserved a record of environmental change and to distinguish environmental sources that may have influenced the isotopic chemistry. Results suggested that carbonate in terra rossa is mainly pedogenic carbonate, and its formation is closely associated with root activities. The δ 13CSOM variations indicate a climate change into warmer and drier conditions at about 6000–8000 a BP, 12000–14000 a BP and 28000 a BP. Plants were more depleted in δ 13C when carbonate precipitated. Compared with the δ 13CSOM, the δ 13CSC tends to reflect more average climate change information. Most large variations of the δ 13CSC and δ 13CSOM between adjacent sampling layers are accompanied with the change in soil color and texture, suggesting a certain connection between the δ 13C and the soil properties. This study found a positive linearity between δ 13CSC and δ 18OSC; a striking different value and correlation coefficient in different sites may provide a meaningful signal of regional climate change.