Changes in abundant and rare microbial taxa that dominated the formation of soil carbon pool during short-term dryland-to-paddy conversion

Land consolidation of dryland-to-paddy conversion (LC-DtPC) has rapidly changed the farmland ecological environment in the short term, thereby affecting the microbial community and its mediated soil carbon sequestration. It is crucial for the improvement and stabilization of food production capacity. However, there is currently a lack of necessary knowledge about the short-term effects of LC-DtPC on the ecological processes of abundant and rare microbial taxa as well as the formation of soil carbon pool. Therefore, this study used field experiments and high-throughput sequencing technology to explore the short-term effects of LC-DtPC on abundant and rare microbial taxa and the mechanism driving soil carbon pool formation. Our results revealed that (1) the alpha diversity of abundant and rare bacteria and rare fungi was decreased by 1.14%, 6.74% and 12.84%, respectively, in the process of LC-DtPC, but the diversity of abundant fungi was increased by 14.09%. LC-DtPC significantly altered the β-diversity of abundant and rare bacterial, and rare fungal communities ( p < 0.05); (2) LC-DtPC lowered the number of core microbes in the network, and reduced the robustness and vulnerability of abundant and rare microbial networks; (3) LC-DtPC significantly reduced soil carbon pool index by 28.75% in the short term ( p < 0.05), and it was closely correlated with bacterial exogenous degradation and metabolism, carbohydrate metabolism, amino acid metabolism, lipid metabolism, and saprophytic fungal abundance; and (4) structural equation modeling revealed that rare bacteria played a bigger role in carbon pool formation than abundant bacteria, and bacteria played a greater role than fungi in the process of carbon pool formation under the synergistic effect of bacteria and fungi. This study explored the changes in abundant and rare microbial taxa and functions, and provided a theoretical basis for an in-depth understanding of soil carbon pool formation and mechanism during the LC-DtPC process.