Cunninghamia lanceolata and understory ferns had positive rhizosphere effects on the temperature sensitivity of soil microbial respiration in a subtropical forest

Rhizosphere processes play a critical role in soil organic carbon (SOC) cycling that is primarily regulated by temperature. Understanding the response of rhizospheric SOC decomposition to global warming, which is called temperature sensitivity (Q(10)), is pivotal for predicting the feedback of SOC cycling to global warming. However, the rhizosphere effects (REs) on Q(10) and their underlying mechanisms in forest ecosystems remain unclear. Here, the REs on Q(10) for Cunninghamia lanceolata and three understory ferns (e.g., Woodwardia japonica, Parathelypteris glanduligera and Microlepia marginata) in a subtropical forest were explored using a novel incubation procedure with periodically changing temperatures based on the mean annual temperature. Our results showed that the positive REs on Q(10) were observed for all plant species, which ranged from 33% to 88%, and P. glanduligera exhibited higher REs on Q(10) than C. lanceolata. The positive REs on Q(10) were associated with the rhizospheric nitrogen (N) availability and microbial properties. The REs on N component (i.e., the REs on total N, NH4+ and NO3- along the first PCA axis), which is the most important driver, had a positive direct effect on the REs on Q(10). Furthermore, the rhizospheric microbial biomass and the REs on microbial residues were also positively related to the REs on Q(10). Overall, these findings highlight that plant-covered soils have high risks of C emissions under planetary warming, underscore the importance of root-soil interactions for accurately predicting SOC dynamics and reveal that rhizospheric nutrients and microbial properties drive the feedback of the root-associated SOC cycle to global warming.