Controls of soil respiration in a salinity-affected ephemeral wetland

Abstract The total efflux of CO2 derived from metabolic processes in soil (Rsoil) exerts a large control on the terrestrial carbon balance. In landscapes that have been radically transformed by humans, the natural carbon balance may be altered by shifts in Rsoil. After accounting for temperature, we sought to determine the main factors that govern Rsoil at Toolibin Lake, an ephemeral wetland threatened by salinization as a result of land clearing. We found strong statistical support for a positive effect of soil gravimetric water content (θ) on Rsoil and weaker support for a negative effect of salinity (measured as the electrical conductivity of a soil extract (ECe)) on Rsoil. We also detected weak support for a positive interaction between θ and ECe, such that θ had a greater positive effect on Rsoil at elevated soil salinities. These results confirm not only that soil moisture is an important driver of Rsoil under native conditions, but also that elevated soil salinities have the potential to accentuate the link between Rsoil and moisture content.