Responses of Q10 to anthropogenic soil redistribution: Synthetic effects of SOM composition and r/K-shifts of microbial community

The temperature sensitivity of soil respiration (Q₁₀) is a pivotal parameter for forecasting the fate of soil carbon (C) under global warming. Although a plethora of studies have elucidated the changes in Q₁₀ in farmland or natural ecosystems, the response of Q₁₀ to soil redistribution remains unclear. A simulated anthropogenic soil redistribution experiment by examining subsoil exposure (E₂₀) and topsoil addition (A₂₀) was performed to explore the influences of soil organic matter (SOM) composition and r/K-shifts of microbial community on Q₁₀. Compared with the undisturbed soil, the average annual Q₁₀ in the E₂₀ plot was significantly increased, whereas the mean annual Q₁₀ in the A₂₀ plot decreased. The ratios of CC to COO and CC to CO, which indicate the stability of SOM, were significantly increased by 14.8%− 44.2% and 33.9%− 45.4% in the E₂₀ plot but decreased by 18.6%− 28.1% and 3.8%− 11.2% in the A₂₀ plot, respectively. The ratios of oligotrophs to copiotrophs in both the bacterial and fungal communities were significantly increased in the E₂₀ plot (K-shift) but decreased in the A₂₀ plot (r-shift). The β-D-xylosidase and cellobiohydrolase activities in the E₂₀ plot were significantly decreased but prominently increased in the A₂₀ plot, whereas the activity of polyphenol oxidase showed the opposite trend. The high aromaticity of recalcitrant SOM in the E₂₀ plot determined the prevalence of K-shift in the bacterial and fungal communities, which might be attributed to the production of enzymes that decompose recalcitrant SOM, which then further enhanced Q₁₀ and vice versa. Overall, our findings indicated that the feedback of ecological strategy of microbial community on the changes in SOM functional groups should be considered when evaluating the response of regional C cycling to anthropogenic soil redistribution.