Effect of wind turbulence on monitoring soil CO2 flux using the closed gas chamber method

Abstract

This study evaluated the performance of closed chamber monitoring of soil carbon dioxide (CO2) flux in a wind turbulence environment to improve the accuracy of constructing an ecosystem carbon budget. The effect of wind turbulence–induced barometric pressure fluctuations on soil CO2 emissions was explored using soil pore pressure difference data from different monitoring sites in the field, and the factors associated with errors in the monitoring of closed gas chambers were analysed. Subsequently, a gas chamber measurement error study was conducted in conjunction with the flux calculation model based on the phenomena observed in the field. The results showed that the simply designed closed gas chamber exerted a strong isolation effect on wind turbulence and did not simulate the actual monitoring environment. The error of the linear flux model in a turbulent wind environment for 10 min was 3%–7% greater than that in the absence of wind (error of 12%), and the calculation error of the exponential fitting model in a turbulent environment was also close to 10%. In addition, the error in the calculation model was positively correlated with the wind turbulence intensity and soil dispersion coefficient. Therefore, for a windy environment, the closed gas chamber and flux calculation models must be improved. Otherwise, a large deviation between the monitored flux and actual values will occur.