PNNL

Abstract

Understanding how soil respiration responds to fluctuations in soil moisture and temperature is increasingly important as climate change intensifies drying and rewetting events and causes soil warming. This study investigated whether the temperature sensitivity of soil respiration (Q10) and its temperature dependence differ between rewetting and dry-down periods. We collated high-frequency field data on soil respiration, soil moisture, and soil temperature from the COSORE dataset (28 sites). Then, for data being partitioned into dry-down and rewetting periods, random forest regressions and accumulated local effects plots were used to assess main effect of temperature on soil respiration. This approach enables estimation of the temperature dependence of Q10 without considering the possible moisture effects. Results showed that the temperature dependence of Q10 differs between the drying and rewetting periods; Q10 is lower during rewetting than during drying in soils with temperatures below 15 °C, but higher in soils with temperatures higher than 15 °C. No differences were found in the temperature dependences of Q10 between rewetting events with large and small respiration pulses. We conclude that the effects of warming on soil respiration differ between dry-down and rewetting periods.