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 (Q(10)) 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 Q(10) in farmland or natural ecosystems, the response of Q(10) to soil redistribution remains unclear. A simulated anthropogenic soil redistribution experiment by examining subsoil exposure (E-20) and topsoil addition (A(20)) was performed to explore the influences of soil organic matter (SOM) composition and r/K-shifts of microbial community on Q(10). Compared with the undisturbed soil, the average annual Q10 in the E-20 plot was significantly increased, whereas the mean annual Q(10) in the A(20) plot decreased. The ratios of C=C to COO and C=C to C=O, 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 A(20) plot, respectively. The ratios of oligotrophs to copiotrophs in both the bacterial and fungal communities were significantly increased in the E-20 plot (K-shift) but decreased in the A(20) plot (r-shift). The beta-D-xylosidase and cellobiohydrolase activities in the E-20 plot were significantly decreased but prominently increased in the A(20) plot, whereas the activity of polyphenol oxidase showed the opposite trend. The high aromaticity of recalcitrant SOM in the E-20 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 Q(10) 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.

Automated summary

This study examined the influence of soil organic matter composition and microbial community shifts on soil respiration temperature sensitivity (Q(10)) through a simulated anthropogenic soil redistribution experiment. The results showed that the average annual Q(10) significantly increased in the subsoil exposed plot and decreased in the topsoil added plot. The stability of soil organic matter and the ratio of oligotrophs to copiotrophs in the microbial communities also varied in response to soil redistribution.