Community assembly processes of soil bacteria and fungi along a chronosequence of rice paddies cultivated on saline-sodic land

Saline-alkali soils cover an area of more than 900 million ha and pose an acute threat to global food security. Rice cultivation is an effective method of saline-sodic soil amelioration in the Songnen Plain in northeastern China. However, the changes in soil microbial communities that follow rice cultivation are largely unknown. In this study, soil bacterial and fungal communities were investigated using high-throughput sequencing along a chronosequence of rice paddies cultivated in saline-sodic soils. The results showed that soil fungi and bacteria become more diverse and abundant after rice cultivation compared with uncultivated saline-sodic soil, in combination with the decreased pH and increased soil organic matter, indicating the amelioration of saline-sodic soil. The processes of microbial succession following rice cultivation can be divided into two stages: shorter than and longer than 10 years. Moreover, soil fungi and bacteria exhibited distinct variation patterns as they were dominated by different influential factors. The results indicated that bacteria were more strongly dominated by soil properties than fungi, while the latter were more dependent on vegetation. As rice cultivation continued, fungi exhibited better adaptation and faster succession than bacteria in response to environmental shifts after rice cultivation. Therefore, measures that can enhance plant-microbe interactions may be a viable approach for promoting saline-sodic soil amelioration. This study provided novel insights into the microbial assembly processes following rice cultivation on saline-sodic lands.