Environmental Stresses Constrain Soil Microbial Community Functions by Regulating Deterministic Assembly and Niche...

Area of Science:

• Ecology
• Microbiology
• Environmental Science

Background:

• Soil microbial alpha-diversity loss due to environmental stress impairs microbial functions.
• The specific impact of microbial alpha-diversity on community functions under stress remains unclear.

Purpose of the Study:

• Investigate how bacterial and fungal alpha-diversity change along environmental stress gradients.
• Evaluate the relationship between microbial diversity and functional traits in grasslands.
• Understand the ecological mechanisms linking microbial biodiversity to ecosystem functioning.

Main Methods:

• Assessed bacterial and fungal alpha-diversity across 45 Chinese grasslands.
• Quantified five natural stressors (temperature, precipitation, plant diversity, soil organic C, pH) into an integrated stress index.
• Utilized metagenomic analyses and phylogenetic null models to analyze gene diversity and community assembly.

Main Results:

• Bacterial and fungal alpha-diversity declined under high environmental stress across soil layers.
• Functional gene diversity decreased along stress gradients.
• High stress increased genes for broad functions (e.g., metabolism, replication) but decreased genes for specialized functions (e.g., C, N, S, methane cycling).
• Stochastic assembly dominated high-diversity communities with narrow niches; deterministic assembly dominated low-diversity communities with wide niches.

Conclusions:

• Low microbial diversity under high environmental stress promotes deterministic assembly and wide niches.
• These processes influence microbial gene abundance, regulating key ecosystem functions.
• Findings highlight the crucial role of microbial biodiversity and assembly mechanisms in terrestrial ecosystem functioning.