Soil moisture controls on temperature sensitivity of soil organic carbon decomposition for a mesic grassland

We examined relationships between soil moisture and the temperature sensitivity of decomposition of labile soil organic carbon at a central North American grassland. For soils collected from shallow, xeric uplands, temperature sensitivity was greatest at intermediate soil moisture. For soils collected from the deeper, mesic lowlands, temperature sensitivity increased with increasing soil moisture. For example, lowland soils incubated at 75% WHC exhibited an apparent activation energy (Ea) that was 15 kJ mol−1 greater than soils incubated at 30% WHC, the equivalent of a Q10 of 2.8 vs. 2.3. Although further research is still needed to understand why moisture–temperature sensitivity relationships would differ between topographic positions, the magnitude of the soil moisture effect is large enough to alter soil C budgets and should be considered explicitly when predicting ecosystem responses to global change scenarios.