Responses of soil bacterial compositions to concentrations of nitrogen forms in the process of Moso bamboo invasion

We analyzed and compared the soil bacterial diversity and difference in community composition in a Moso bamboo forest, a mixed Moso bamboo–conifer ( Pinus massoniana ) forest, and a coniferous forest. The relative abundances of Acidobacteria and Planctomycetes were significantly lower in the Moso bamboo forest, while those of Actinobacteria, Bacteroidetes, TM‐7 and Chlamydiae were greatly increased. The α‐diversity in the Moso bamboo forest was different from that in the other two forest types but was not statistically distinguished. Principal coordinates analysis suggested that the invasion of Moso bamboo affected the community composition and diversity of soil bacteria. This impact was associated with the soil biochemical environment, as evidenced by increased mean values of soil organic carbon (C) and total nitrogen (N), significant increases in microbial biomass C and N, and a decrease in the NO 3 − –N content, which indicated that the nitrification rate was reduced in the mixed Moso bamboo–conifer forest. There were no overall correlations between the dominant bacterial phyla and soil biochemical gradients; however, individual dominant phyla correlated with the concentration of N forms, which indicated that the responses of bacteria were sensitive to, and varied depending on, the concentration of soil N forms. In addition, there were correlations between non‐dominant bacterial phyla with respect to operational taxonomic unit proportions <1.0%, and overall gradients of water‐soluble organic N and NO 3 − –N. The results of this study showed that the changes in soil bacterial flora are associated with the changes in concentration of N forms during the invasion of Moso bamboo.