Dynamics and potential drivers of CO2 concentration and evasion across temporal scales in high-alpine streams

Abstract

Carbon dioxide (CO _2 ) evasion from streams greatly contributes to global carbon fluxes. Despite this, the temporal dynamics of CO _2 and its drivers remain poorly understood to date. This is particularly true for high-altitude streams. Using high-resolution time series of CO _2 concentration and specific discharge from sensors in twelve streams in the Swiss Alps, we studied over three years the responsiveness of both CO _2 concentration and evasion fluxes to specific discharge at annual scales and at the scale of the spring freshet. On an annual basis, our results show dilution responses of the streamwater CO _2 likely attributable to limited supply from sources within the catchment. Combining our sensor data with stable isotope analyses, we identify the spring freshet as a window where source limitation of the CO _2 evasion fluxes becomes relieved. CO _2 from soil respiration enters the streams during the freshet thereby facilitating CO _2 evasion fluxes that are potentially relevant for the carbon fluxes at catchment scale. Our study highlights the need for long-term measurements of CO _2 concentrations and fluxes to better understand and predict the role of streams for global carbon cycling.

Keywords

• high-alpine streams
• CO2 evasion fluxes
• responsiveness to runoff
• spring freshet
• carbon fluxes