Soil Bacterial Diversity and its Determinants in the Riparian Zone of the Lijiang River, China

This study was designed to analyse the soil bacterial community composition and diversity, as well as their relationships with various environmental factors in a riparian ecosystem. The 16S rRNA sequencing technology was applied to profile the bacterial composition of 120 samples from four different transects (long, moderate, less and rare inundation) in ten different study sites along the Lijiang riparian zone; the corresponding soil properties were also measured. The results indicated that, diversity was lowest in the rare inundation transect and there were high yet not significantly different bacterial community diversities in the long, moderate, and less inundation transects. The dominant bacterial groups of the four transects were similar, but there were great differences in the abundances of specific groups. Proteobacteria (29.28%), with the dominant classes of Beta- (15.65%), Delta- (5.75%), Gamma- (4.46%) and Alpha-proteobacteria (3.32%), was the most abundant phylum in the studied riparian soils. The genus Candidatus Nitrososphaera including ammonia-oxidizing archaea (AOA) and the genus Nitrospira including nitrite-oxidizing bacteria were both sensitive to inundation gradient changes. Redundancy analysis revealed that soil properties such as soil pH, inundation frequency, sand content, soil water content, total N and available N were significantly correlated with the bacterial community diversity and structure. The study suggests that the flood disturbance gradient and the spatial heterogeneity of soil properties affect the composition and diversity of bacterial communities in the Lijiang riparian zone.