[Comparison of Bacterial Community Structure in Soil Aggregates Between Natural Karst Wetland and Paddy Field]

Studying the impact of land-use changes in wetland systems on the community structure of bacteria in soil aggregates can provide a theoretical basis for elucidating the impact mechanisms of the stability of wetland soil aggregates. The soil samples (0-20 cm) were collected from a natural wetland and paddy field in the Huixian karst wetland. The bacterial community structure in soil aggregates (macroaggregates 0.25-2 mm, microaggregates 0.053-0.25 mm, and silt-clay<0.053 mm) were analyzed using high-throughput sequencing and ecological network analysis. The results showed that ① the proportion of microaggregates in the paddy field was 29.64%, which was significantly higher than that in the natural wetland (22.20%), and ② there were differences in the relative abundance of bacteria between the natural wetland and paddy field. The relative abundance of Chloroflexi in macroaggregates, microaggregates, and silt-clay in the paddy field were 7.97%, 8.56%, and 7.40%, respectively, which were significantly higher than those in the natural wetland (4.93%, 4.81%, and 3.76%). The relative abundance of Anaerolineales in macroaggregates, microaggregates, and silt-clay in the paddy field were 2.35%, 3.03%, and 2.65%, respectively, which were significantly higher than those in the natural wetland (0.92%, 0.91%, and 0.43%).③ Ecological network analysis showed that the number of nodes, edges, and the average numbers of neighbors in microaggregates and the silt-clay network in the paddy field were higher than those in the natural wetland, the average connectivity of the network was greater in the two components, and the characteristic path length was shorter. There was a longer characteristic path length, higher modularity, and lower average connectivity in the macroaggregate network of the paddy field. The above results indicated that the bacterial community structure in soil aggregates was altered after a natural wetland was used as a paddy field. The material circulation and information transmission efficiency of bacterial communities was higher in both microaggregates and silt-clay of the paddy field, whereas the bacterial community structure with low network tightness and high modularity in macroaggregates was more stable.