Depth-Dependent Patterns of Bacterial Communities and Assembly Processes in a Typical Red Soil Critical Zone

Abstract

Depth patterns of soil microbial distribution have not been well characterized and little is known about the balance between stochastic and deterministic processes in shaping microbial community through soil profiles. We examined how the composition, diversity, and assembly processes of bacterial communities change to a depth of 4 m along three cores sampled through a typical upland red soil Critical Zone in subtropical China. The sampled soils at the center of the Critical Zone were acidic, highly weathered, and clay loam to clay in texture, and developed from Quaternary red clay. Bacterial richness and phylogenetic diversity decreased with depth in the upper soil zone (0–90 cm), but was constant in the deeper zone (90–420 cm). In both the upper and deeper zones, richness was strongly and positively correlated with total organic carbon, dissolved organic carbon and total nitrogen. Depth-dependent changes of community structure were observed above the upper but not deeper zones. Stochastic processes were more important in the upper zone, whereas deterministic processes were dominant in the deeper zone. The distinct depth-dependent patterns of bacterial communities and assembly processes exist through deep soil profiles and are influenced by both contemporary and historical pedogenetic factors and processes.

Keywords:

• Bacterial community
• bacterial distribution
• community assembly
• soil profile
• red soil Critical Zone

Acknowledgments

We thank David G. Rossiter (Cornell University) for his help with the English language presentation and clarity of the argument.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the National Natural Science Foundation of China [41571130051, 41977003 and 41501228], the Frontier Program of the Institute of Soil Science, Chinese Academy of Sciences [ISSASIP1625], and the Strategic Priority Research Program of the Chinese Academy of Sciences [XDB15010101].