Environmental controls on the temperature and moisture sensitivity of soil respiration during drying and rewetting events

Understanding the moisture and temperature sensitivity of soil respiration is important as climate change brings more variation in soil moisture (e.g., drought, drying, and rewetting events) and soil temperature (e.g., warming). However, soil moisture and soil temperature sensitivity of soil respiration are often assumed fixed, neglecting environmental controls that might modulate them. Moreover, the soil moisture sensitivity is likely different during drying as opposed to rewetting periods due to the different processes involved, and soil temperature sensitivity is often estimated without separating the drying and rewetting periods, during which processes with contrasting temperature sensitivity are dominant. Here, we collected high-frequency field data on soil respiration, soil moisture, and soil temperature from COSORE (27 sites) and NEON (47 sites) and defined the moisture and temperature sensitivity of soil respiration in both the drying and rewetting periods. Using the monthly standardized precipitation evapotranspiration index (SPEI) and monthly temperature over the last 30 years of each site, we characterized the historical climate conditions by drought frequency and temperature amplitude. Then, the moisture and temperature sensitivity of soil respiration in both the drying and rewetting periods were explained by historical climate conditions, vegetation index, soil properties, and their interactions. The results will provide a better understanding of the environmental controls on soil moisture and temperature sensitivity of soil respiration.