Analyzing High‐Frequency Soil Respiration Using a Probabilistic Model in a Semiarid, Mediterranean Climate Journal of Geophysical Research: Biogeosciences

High‐frequency (subhourly) changes in soil respiration (Rs), a critical component of the carbon cycle, are not well documented in semiarid ecosystems. We investigate the response of Rs to subhourly soil temperature (Tsoil) and soil volumetric water content (VWC) variation in a semiarid ecosystem across a year of highly variable weather. We propose a probabilistic model to estimate the likelihood of Rs exceeding its annual mean (1.2 μmol CO2/m2s), conditioned on different Tsoil and VWC values. The results show that Rs follows a Gaussian‐like pattern as Tsoil increases, where it follows an upward trend until ~18 °C, and then begins to decline. Rs remains constant at Tsoil beyond ~27 °C. Using our novel conditional probability model, we show both the increasing and decreasing response of Rs to rising Tsoil through two ranges (14–17 and 20–23 °C) where Rs observations show opposing responses. We demonstrate that an increase in Tsoil from 14 to 17 °C causes a rise in Rs by a factor of 1.4 relative to the mean. The proposed model also describes how Rs reduces as Tsoil continues to increase above ~18 °C. Considering VWC and Tsoil into the proposed model, we show that when Tsoil is low (e.g., 17 °C), a rise in VWC yields a decrease of Rs by a factor of 3.6. However, when Tsoil is high (e.g., 23 °C), Rs increases with increasing VWC by a factor of 2.5. Overall, the probabilistic model enables us to detect and characterize changes in Rs distribution in response to different environmental variables and thresholds. Grant no. NA14OAR4310222