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

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.
This research was funded by the Andalusian regional government projects GEOCARBO (P08‐RNM‐3721) and GLOCHARID, including European Union ERDF funds, with support from European Community’s Seventh Framework Programme (FP7/2007‐2013) under grant agreement 244122 and Spanish Ministry of Science and Innovation projects PROBASE (CGL2006‐11619/HID) and (Carbored‐II; CGL2010‐22193‐C04‐02).