Tree diversity affects temperature sensitivity of soil organic matter decomposition in rhizosphere

Background and aims: Tree diversity strongly regulates organic matter inputs by rhizodeposition for microorganisms and microbial communities, impacting soil carbon (C) dynamics and stability. Because of much larger organic C availability in the rhizosphere, it can respond differently to tree diversity compared to bulk soil. To explore soil C stability under global warming, we assessed the temperature sensitivity (Q10) of organic matter decomposition in rhizosphere and bulk soil depending on tree diversity. Methods: Q10 of organic matter decomposition in rhizosphere and bulk soil in a subtropical forest were examined using short-term incubation under controlled conditions depending on tree diversity. Fine root traits and soil C and N availability were evaluated as related to microbial properties. Results: With increasing tree diversity, Q10 remained stable in the rhizosphere but decreased in the bulk soil. While greater tree diversity increased fine root biomass, soil C and N availability, microbial K/r strategy ratios in rhizosphere and bulk soil shifter towards the r strategists, with a reduced bacterial K/r strategy ratio. However, microbial gene copy numbers and Shannon diversity remained stable. Partial correlation and multiple regression analysis revealed that rhizosphere Q10 remained stable because of C excess and larger microbial abundance. The Q10 reduction in bulk soil correlated with increased C availability and a shift in microbial community towards a lower K/r strategy ratio. Conclusion: The Q10 decoupling between rhizosphere and bulk soil highlights a trade-off, where increasing tree diversity accelerates organic matter decomposition in rhizosphere to sustain nutrient supply, while maintaining bulk C pool stability under global warming. © 2025 Elsevier B.V., All rights reserved.