Labile Carbon Addition Alters Soil Organic Carbon Mineralization but Not Its Temperature Sensitivity in a Freshwater Marsh of Northeast China

Inland freshwater marshes are notable contributors to soil organic carbon (SOC) pool across the globe. Input of labile C can greatly affect the direction and intensity of priming effects (PE) on SOC decomposition, which will likely be altered under climate warming. However, the effects of temperature on priming of wetland SOC mineralization and its temperature sensitivity (Q(10)) under varied C inputs remain unclear. We conducted a laboratory incubation experiment with C-13-glucose addition to investigate the effects of labile C on priming and Q(10) values of the freshwater wetland SOC decomposition at 10 and 20 degrees C in Northeast China. Results showed that temperature and glucose additions had significant effects on CO2 efflux rates, but interactive effects were not observed. The positive priming that increased with increasing C added at both temperatures was detected, while the magnitude of priming at 10 degrees C was higher than that at 20 degrees C. There were no significant differences in Q(10) values under low and high glucose additions, both of which were obviously lower than that of no glucose addition treatment. Total microbial biomass (total PLFAs) at 20 degrees C was significantly decreased compared to that at 10 degrees C, while the opposite trend was observed for CO2 efflux at the end of incubation. High glucose addition induced higher PLFAs than other treatments at both temperatures, but the composition of microbial community was not significantly altered by temperature under labile additions. We conclude that substrate availability and temperature change may have great impacts on wetland soil C turnover through priming effects. We highlight that more attention should be paid on the relationship between labile substrates and temperature sensitivity of decomposition under climate warming.