Soil microorganisms are important components of the soil ecosystem, and they play critical roles in biogeochemical and nutrient cycling processes. Due to the dramatic changes in soil properties across the soil profile, soil microbial biomass, diversity and composition differ significantly between soil layers. The vertical pattern and variation in bacterial communities are critical for predicting belowground processes. But the vertical variation in bacterial communities in natural forests keeps unknown.

In order to identify the vertical pattern and variation in soil bacterial community in natural forests, and to reveal their determining factors, the Global Change Biology Group led by Prof. LIU Feng of Wuhan Botanical Garden presented a study in five forests types in the Taibai Mountain and explored the diversity and composition of soil bacterial community using 16S rRNA gene sequencing.

This study revealed that soil layer significantly affected soil bacterial diversity and composition. Soil carbon availability and the oligotrophic-copiotrophic theory (copiotrophic taxa were enriched in surface soils with high resource availability, whereas oligotrophic taxa survived in the deep layers where resources are scarce) can dominantly explain the vertical distribution of soil microbial communities. Deterministic processes based on environmental heterogeneity governed the assembly of soil bacterial communities within each soil profile.

Vertical variations in soil bacterial communities differed among forest types. Soil bacterial composition in the Betula albo-sinensis forest at the medium elevation had lower vertical spatial variation than other forests. High mean annual precipitation and the rocky texture can explain the higher vertical homogeneity in the B. albo-sinensis forest, which probably due to the stronger vertical transport of soil microorganisms with water flux.

These results emphasize the strong linkage between climate condition and vertical variation in soil bacterial communities and could potentially help us better predict belowground functions.

The research entitled “Vertical distribution of soil bacterial communities in different forest types along an elevation gradient” was published in Microbial Ecology. This work was supported by the National Natural Science Foundation of China, and the Youth Innovation Promotion Association, CAS.

Vertical variations in soil bacterial communities differed among forest types (Image by WBG)
 

Factors controlling the vertical variation in soil bacterial community (Image by WBG)