Vertical difference of soil CO2 flux and its driving factors in Loess Hilly Region, China

The diffusion of carbon mineralization in vertical profiles is an important process of CO2 emission. However, due to the relatively slow and lagging change of subsoil environment compared with the surface soil, the process of carbon mineralization and diffusion is often ignored, and the process and mechanism of deep carbon transfer to the soil-atmosphere interface are still unclear. we studied the vertical difference of CO2 flux and its driving mechanism in Robinia pseudoacacia plantation of different stand ages. The results show that: (1) in the 0-200cm layer, the CO2 flux shows a double peak seasonal trend. Among them, the total CO2 flux of Robinia pseudoacacia forest in 10 years was larger. (2) Dynamic evaluation can reduce the uncertainty of static evaluation, and the contribution of deep CO2 flux to the soil atmosphere interface is stable, between 21.81-24.42%; (3)Temperature sensitivity of CO2 flux (expressed as Q10) significantly increases with soil depth, and the response of water to CO2 flux is different at different section. There is a significant correlation between the deep CO2 flux and soil organic carbon (SOC), but there is a reverse feedback effect in the shallow profile. (4) T & M & C model is more conducive to the accurate prediction of deep CO2 flux. All in all, this study is of great significance to the study of the stability of deep soil carbon, the dynamic change of soil carbon pool and the mechanism of deep carbon diffusion to the surface in the loess hilly area.