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.