Characterization of subsoil co2 dynamics in two semiarid ecosystems: global scale implications

Abstract

Rates of biological activity per unit of drylands are low compared with many terrestrial ecosystems but the large surface area of drylands gives their carbon dynamics a relevant global significance. In particular, variability in the global CO2 sinks is dominated by that semi-arid ecosystems, which are the ecosystems most vulnerable to climate change and can be switched to a CO2 source in response to global warming or changes in precipitation. Under this premise, subterranean ventilation could be the most important factor determining the variability in the annual ecosystem carbon balance in many ecosystems around the world. Understanding the occurrence of processes, feedbacks and driving factors that modulate the carbon source capacity of natural ecosystems due to ventilation events is needed to advance towards more robust model projections for future climate as well as more adequate design of mitigation policies. Additionally, the improvement of the gradient method, considering the role of abiotic factors in deep soil CO2 dynamics, will be essential to produce reliable estimations of soil CO2 efflux in ecosystems affected by non-diffusive gas transport processes.