Contrasting patterns of microbial community and enzyme activity between rhizosphere and bulk soil along an elevation gradient

The distribution patterns of the microbial community and enzyme activity in soil systems along an elevation gradient have attracted considerable attention; however, the differences in microbial diversity and enzyme activity between the rhizosphere and bulk soil and their drivers are still unclear. Here, we used an elevation gradient that covered six elevation levels and ranged from 1308 to 2600 m above sea level. Illumina MiSeq sequencing of the 16S rRNA gene and ITS-1 gene was used to analyze the community of bacteria, total fungi, ectomycorrhizal (EcM) fungi, and saprotrophic fungi in both rhizosphere and bulk soil; in addition, the soil enzyme activity (β-glucosidase, N-acetyl-glucosaminidase, leucine aminopeptidase, and acid phosphatase) was investigated. The results revealed that the elevation significantly affected the diversity of the bacterial, total fungal, EcM, and saprotrophic fungal community, as well as the enzyme activity dynamics. The difference in the microbial diversity and enzyme activity between rhizosphere and bulk soil diminished as the elevation increased, except for the saprotrophic fungal diversity. Similarly, the dominant phyla from the compositions of bacteria, fungi, EcM fungi, and saprotrophic fungi, such as Proteobacteria, Acidobacteria, Actinobacteria, Basidiomycota, and Ascomycota, also changed with elevation and rhizosphere. In addition, the elevation-dependent differences in the microbial community and enzyme activity between the rhizosphere and bulk soil were affected mainly by climatic factors (mean annual temperature and precipitation) and soil properties, such as the bulk density, ammonium nitrogen, and total phosphorus. The effects of the climatic factors were greater than those of the soil properties along the elevation gradient. These results suggest that changes in climatic factors, such as temperature, with elevation may affect the microbial interaction between roots and the soil. The result highlight the importance of the ecological roles of the microbial community in climate change.