Xiujun Wang¹, Jiaping Wang², Yang Guo¹,Xianglan Li¹

　　¹ College of Global Change and Earth System Science, Beijing Normal University, Xinjiekouwai Street No.19, Haidian District, Beijing 100875, China

　　²College of Agriculture, Shihezi University, Shihezi 832003, Xinjiang, China

　　Soil carbonate (SIC)exceeds organic carbon (SOC) greatly in arid and semi-arid lands, thus may be important for carbon sequestration. However, field data forstudying SIC dynamics and quantifying SIC accumulation have been lacking. To address this issue, we have conducted a few studies in north China. This paperprovides a summary of our recent findings.

　　SIC accumulation was quantified using two sets of data: >100 soil samples recently collected from the Yanqi Basin of central Xinjiang and ~200 archived soil samples from four long-term experiment (LTE) sites in the north China.Our study showed that intensive cropping in the arid and semi-arid region leaded to a greater increase in SIC than in SOC; organic amendments enhanced SIC accumulation in the cropland of north China.

　　In addition, we collected 155 soil samples from 31 profiles in the upper Yellow River Delta of North China Plain. Our analyses showed that there was a significantly positive correlation (Figure 1) between SOC and SIC in the cropland; SIC had a significantly positive correlation with both soluble Ca²⁺ (r = 0.57, P < 0.01) and Mg²⁺(r = 0.43, P < 0.05). Our study suggested that increasing SOC might lead to an increase in SIC stocks in the cropland of north China.

　　Figure 1. Relationship between soil inorganic carbon (SIC) and organic carbon (SOC) stocks in the 0−30 cm (a) and 0−100 cmsoil layers(b).