Straw addition decreased the resistance of bacterial community composition to freeze–thaw disturbances in a clay loam soil due to changes in physiological and functional traits

• Bacterial community in straw-added soils was less resistant to freeze–thaw cycles. • Changes in bacterial composition was related to ecological trait-based responses. • Freeze-thaw cycles promoted bacteria mining more soil C under straw addition. Crop residues are usually returned into the soil after autumn harvest and maintained throughout the winter and early spring in temperate regions. This agricultural practice may exert important effects on soil microbial communities, consequently changing their compositional and functional stability to freeze–thaw disturbances later in the autumn and early spring. In this study, we examined the effect of straw addition on the composition and function of bacterial communities subjected to different intensities of freeze–thaw cycles in a clay loam soil. Bacterial composition in the control soils varied little after different freeze–thaw cycles. Freeze-thaw cycles, however, significantly changed the bacterial community composition in the straw-amended soils towards a less resistant community that was more vulnerable to freeze–thaw stress. A further analysis showed that straw addition significantly decreased bacterial alpha diversity and shifted soil bacterial community composition to one dominated by copiotrophs. Based on function predictions, the bacterial communities in the straw-amended soils presented superior competitive traits but inferior stress-tolerant and ruderal traits as compared to those in the control soils. Our results suggest that straw addition decreased the resistance of soil bacterial community composition to freeze–thaw disturbances through changes in their physiological and functional traits. These findings implicate that freeze–thaw cycles could exert important consequences on the functioning of agroecosystem when straw is returned into the soil.