Carbon quality and soil microbial property control the latitudinal pattern in temperature sensitivity of soil microbial respiration across Chinese forest ecosystems

Abstract Understanding the temperature sensitivity ( Q 10 ) of soil organic C ( SOC ) decomposition is critical to quantifying the climate–carbon cycle feedback and predicting the response of ecosystems to climate change. However, the driving factors of the spatial variation in Q 10 at a continental scale are fully unidentified. In this study, we conducted a novel incubation experiment with periodically varying temperature based on the mean annual temperature of the soil origin sites. A total of 140 soil samples were collected from 22 sites along a 3,800 km long north–south transect of forests in China, and the Q 10 of soil microbial respiration and corresponding environmental variables were measured. Results showed that changes in the Q 10 values were nonlinear with latitude, particularly showing low Q 10 values in subtropical forests and high Q 10 values in temperate forests. The soil C:N ratio was positively related to the Q 10 values, and coniferous forest soils with low SOC quality had higher Q 10 values than broadleaved forest soils with high SOC quality, which supported the “C quality temperature” hypothesis. Out of the spatial variations in Q 10 across all ecosystems, gram‐negative bacteria exhibited the most importance in regulating the variation in Q 10 and contributed 25.1%, followed by the C:N ratio (C quality), fungi, and the fungi:bacteria ratio. However, the dominant factors that regulate the regional variations in Q 10 differed among the tropical, subtropical, and temperate forest ecosystems. Overall, our findings highlight the importance of C quality and microbial controls over Q 10 value in China's forest ecosystems. Meanwhile, C dynamics in temperate forests under a global warming scenario can be robustly predicted through the incorporation of substrate quality and microbial property into models.