Coupling between surface- and ground-carbon cycling delineated by millifluidics: Implications for soil respiration in a changing environment The respiratory release of carbon dioxide (CO2) from the Earth’s soil into the atmosphere is a major, yet poorly understood, flux in the global carbon cycle. Understanding soil respiration sensitivity to elevated atmospheric CO2 (eCO2) and/or climatic warming remains one of the key sources of uncertainty in projecting terrestrial carbon balance and likely future shifts in the global climate. This study aims to deepen our mechanistic understanding of hidden mechanisms neither accounted for by large-scale Earth system models nor readily quantified by field experiments. We specifically explore the role of leaf-level response to eCO2 and/or temperature in regulating soil moisture (water saving effects) and the resulting impacts on CO2 release from soil due…