Temperature Sensitivity of Soil Organic Carbon Mineralization Is Regulated by Exogenous Organic Matter Forms and the Degree of Soil Salinization

The objectives of this study are to explore the effect of different forms of straw from the same source on the temperature sensitivity of soil organic carbon (SOC) mineralization in saline soils and to determine the practicability of granular straw addition to saline soils. Chopped wheat straw (CW), granular wheat straw (GW), and wheat straw biochar (BW) were used as exogenous SOC materials, and no straw was used as the CK. Through incubation experiments, the mineralization characteristics and temperature sensitivity of the three exogenous organic materials with equal amounts of added carbon were studied at different temperatures (10 °C, 20 °C, 30 °C) and different soil salinity levels (mild, moderate, severe). At equal carbon addition, the SOC content in the BW and GW treatments increased by 58.90% and 21.77%, respectively, compared with CW. At the end of incubation, the SOC mineralization rate and cumulative carbon mineralization increased significantly in CW and GW. Compared with that in BW, the cumulative carbon mineralization in CW and GW increased by 4.34 and 4.81 times, respectively. The Q10 value in BW, CW, and GW was significantly lower than that in CK. The Q10 value in GW was lower than that in CW and BW. With the same amount of carbon application, granular straw return is an effective soil carbon sequestration strategy, because it can compensate for the disadvantages of the conventional form of straw and biochar return. Granular straw return can significantly decrease the temperature sensitivity of SOC mineralization, especially at low temperatures.