Dynamics of Soil CO2 and CO2 Efflux in Arid Soil

Abstract

Soil carbon dioxide (CO2) is an important component in the terrestrial ecosystem and regulates the atmosphere–land CO2 exchange. Studying the variation of CO2 in soil profile and surface CO2 efflux can improve our understanding of the carbon cycle in the terrestrial ecosystem. In this paper, we analyze the dynamics of soil CO2 and CO2 efflux in an arid region, Yanqi, northwest China. Both CO2 concentration and surface CO2 efflux showed a clear seasonal variation, with two peaks in summer and a gradual decrease in autumn. We found that surface CO2 efflux was exponentially related to soil temperature and linearly related to moisture when soil moisture was less than ~22%. We estimated surface CO2 efflux by linear regression of CO2 fluxes that were calculated by gradient method using Penman (1940), Marshall (1959), and Moldrup et al. (2013) models and found that the Marshall (1959) model did a better job than the other two models. However, there were considerable mismatches between the observation and model results. Our study indicates that the relationship is complex between the concentration of CO2 in soil profile and surface CO2 efflux in the arid region.