Effects of a mixed plantation of Robinia pseudoacacia and Fraxinus velutina on soil bacterial structure and diversity in the Yellow River Delta

In order to investigate the effects of a mixed plantation of Robinia pseudoacacia and Fraxinus velutina on soil bacterial structure and diversity in the Yellow River Delta, the soil bacterial community structure and diversity in pure and mixed plantations of Robinia pseudoacacia and Fraxinus velutina were analyzed using high-throughput sequencing technology. The results showed the following: there were 36 phyla of bacterial communities in pure and mixed plantations of R. pseudoacacia and F. velutina. Acidobacteria, Proteobacteria, and Actinobacteria were the dominant bacterial taxa for the two pure forests and the mixed forest, each with a relative abundance of more than 10%, and Nitrospirae was the dominant bacterial taxon for R. pseudoacacia. The relative abundance of bacteria in the mixed plantation of R. pseudoacacia and F. velutina were significantly different from those in the pure plantations. Among these three plantation types, observed species (1934.5), Chao 1 index (2629.1), and Shannon index (9.1) were highest in the mixed forests. There was a significant positive correlations (0.995*) between soil water content and the quantity of Actinobacteria. Soil pH had a very significant positive correlation (0.999**) with the quantity of Gemmatimonadetes, and a very significant negative correlation (-0.909) with the quantity of Acidobacteria. Soil bacterial diversity showed a very significant positive correlation with soil water content, and a very significant negative correlation with soil available K. The results showed differences in structure and diversity of the soil bacterial community between the pure and mixed stands of R. pseudoacacia and F. velutina. Having changed the structure of bacterial community and increased bacterial diversity, the mixed plantation of R. pseudoacacia and F. velutina had differences in structure and diversity of the soil bacterial community from the two pure forests.