Evaluation of soil CO₂ efflux and its influence factors in a revegetated area in Tengger Desert, NW China

Soil profile CO2 transport and production are vital in the carbon stock in desert artificial vegetation ecosystem. In this study, soil profile CO2 concentration, soil water content, and temperature at depths of 0-40 cm were measured at four revegetated sites (1956, 1964, 1981, and 1987), located in the southeastern edge of Tengger Desert, China. The gradient method was applied to simulate soil gas diffusion coefficient and soil profile CO2 efflux. Soil CO2 efflux and production were significantly higher in upper layers than in bottom layers. The soil profile CO2 concentration, CO2 efflux, and production were not significantly increased with revegetation age. The simulated soil surface CO2 efflux were 0.54, 0.49, 0.44, and 0.25 mu mol center dot m(-2)center dot s(-1) at 1956, 1964, 1981, and 1987 revegetated sites, respectively. The soil surface CO2 efflux mainly came from the 0-10 cm layers, contributing to 76.4-94.9% of the total. CO2 uptake occurred in the 10-35 cm soil layer. Structural equation modelling explained 97.0% of the variations in soil surface CO2 efflux. The effects of soil CO2 concentration, temperature, and water content in the 10-cm layer and plant properties on soil surface CO2 efflux were 0.977, 0.516, - 0.358, and - 0.156, respectively. Interaction between soil temperature and water content was significant and the value was 0.439, indicating that the soil temperature and water content significantly influenced soil CO2 efflux. These results indicated that revegetation would not significantly affect the soil surface CO2 efflux and provided some theoretical basis for the study of soil carbon cycle mechanism in desert artificial vegetation ecosystem.