关键词: 土壤碳, 稳定同位素, 剖面特征, 次生碳酸盐, 碳转移

Abstract: In this study， the desert steppe in Siziwangqi， Inner Mongolia was used as the study area to investigate the vertical distribution characteristics of soil carbon， and the stable carbon isotope technique was used to differentiate lithogenic carbonate（LC） and pedogenic carbonate（PC）， to quantify the amount of fixed CO₂ and the proportion of the source in the formation process of PC， and finally to quantify the transfer of SOC to SIC. The results showed that in the plant growth period， the SOC content in the soil was 3.38-10.84 g·kg^-1 and 3.44~12.28 g·kg^-1， respectively， and both of them showed a decreasing trend with the deepening of the soil layer； the carbonate content in the soil was 28.14-189.61 g·kg^-1 and 27.47-192.13 g·kg^-1， showing an increasing and then decreasing trend with the deepening of the soil layer. During the plant growth period， the PC content in the soil layers of 40-60 cm， 60-80 cm and 80-100 cm were 82.40， and 25.44 g·kg^-1， the amount of fixed CO₂ was 18.13， 24.87 and 5.60 g·kg^-1； and the proportion of soil respiration from the source was 56.91%， 51.91%， and 65.91%， respectively. Soil respiration released CO₂ was the main contribution. Finally， the amount of SOC transferred to carbonate in the three soil layers was calculated to be 5.16， 6.46， and 1.84 g·kg^-1. This study had a preliminary investigation of carbon transfer and provided a theoretical basis for subsequent research on the “carbon cycle”.

Key words: Soil carbon, Stable isotope, Profile characterization, Pedogenic carbonate, Carbon transfer