Subterranean CO2 ventilation and its role in the net ecosystem carbon balance of a karstic shrubland

Abstract

Recent studies of carbonate ecosystems suggest a possible contribution of subterranean ventilation to the net ecosystem carbon balance. However, both the overall importance of such CO₂ exchange processes and their drivers remain unknown. Here we analyze several dry-season episodes of net CO₂ emissions to the atmosphere, along with soil and borehole CO₂ measurements. Results highlight important events where rapid decreases of underground CO₂ molar fractions correlate well with sizeable CO₂ release to the atmosphere. Such events, with high friction velocities, are attributed to ventilation processes, and should be accounted for by predictive models of surface CO₂ exchange.