干旱区生态环境知识资源中心

Soil organic carbon (SOC) and inorganic carbon (SIC) are important carbon reservoirs in arid and semi-arid regions. Field data for quantifying both SOC and SIC in deep soils have been lacking. A study was carried out to evaluate soil carbon stocks in the loess of Lanzhou, a typical semiarid area of northwestern China. Soil samples were mainly collected from profiles of upper 2 meters in irrigated and non-irrigated agricultural land. Our data showed that SOC content decreased with depth, from 7.0 +/- 2.0 g kg(-1) in the 00.2 m to less than 3.0 +/- 2.0 g kg(-1) below 1 m. There was a large variation (311 g kg(-1)) in SOC of the topsoil (00.2 m) but a narrow range of 15 g kg(-1) below 1.0 m. Soil inorganic carbon content showed little vertical changes with mean value of 16.0 +/- 2.5 g kg(-1) in the 02 m, but a considerable spatial variation of 10 21 g kg(-1) in the topsoil. Irrigation slightly enhanced SIC stock in the whole soil profile, with 10% increase in the 030 cm. We estimated that SOC stock was approximately 10 kg C m(-2) for the 02 m, and the SIC stock was about four times of the SOC stock. The SOC and SIC stocks in the subsoil (12 m) were 40% and 50% of the stocks over the 02 m, respectively. The estimated total carbon stock was 26.8 kg C m(-2) over the 01 m, but 50.0 kg C m(-2) over the 02 m. Our study implies that neglecting deep soil may lead to underestimation of soil carbon stock by 50% in the loess. (C) 2014 Elsevier B.V. All rights reserved.