Bacterial community dynamics explain carbon mineralization and assimilation in soils of different land-use history

Soil dwelling microorganisms are key players in the terrestrial carbon cycle, driving both the degradation and stabilization of soil organic matter. Bacterial community structure and function vary with respect to land use; yet the ecological drivers of this variation remain poorly described and difficult to predict. We conducted a multi-substrate DNA-stable isotope probing experiment across cropland, old-field, and forest habitats to link carbon mineralization dynamics with the dynamics of bacterial growth and carbon assimilation. We tracked the movement of C-13 derived from five distinct carbon sources as it was assimilated into bacterial DNA over time. We show that carbon mineralization, community composition, and carbon assimilation dynamics all differed with respect to land use. We also show that microbial community dynamics affect carbon assimilation dynamics and are associated with soil DNA content. Soil DNA yield is easy to measure and may be useful in predicting microbial community dynamics linked to soil carbon cycling. Soil dwelling microorganisms are key players in the terrestrial carbon cycle, driving both the degradation and stabilization of soil organic matter. Microbial communities vary with respect to land use, but we still have an incomplete understanding of how variation in community structure links to variation in community function. DNA stable isotope probing (DNA-SIP) is a high-resolution method that can identify specific microbial taxa that assimilate carbon in situ. We conducted a large-scale multi-substrate DNA-SIP experiment to explore differences in bacterial activity across land-use regimes. We show that microbial community dynamics vary with land use, that these dynamics are linked to soil carbon cycling, and that they are associated with easily measured soil properties.

Automated summary

Soil dwelling microorganisms play a crucial role in the carbon cycle by both degrading and stabilizing soil organic matter. However, the factors that drive the variation in bacterial community structure and function with respect to land use are still poorly understood. In this study, a multi-substrate DNA stable isotope probing experiment was conducted to examine the dynamics of bacterial growth and carbon assimilation in different land-use habitats. The results showed that carbon mineralization, community composition, and carbon assimilation dynamics all varied with land use. Furthermore, microbial community dynamics were found to influence carbon assimilation dynamics and were associated with soil DNA content. The findings suggest that soil DNA yield, which is easily measurable, may be a useful indicator for predicting microbial community dynamics related to soil carbon cycling.