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Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations
Published on: September 11, 2016
Moisture-mediated resource availability shapes rhizosphere and bulk soil microbial structure and function
Hengsheng Wang1,2, Yanli Han3, Chao Chen4
1School of Biological and Food Engineering, Hefei Normal University, Hefei, China.
Introduction:
Rainfall pulses drive rapid ecological changes in alpine grasslands, but their compartment-specific effects on short-term soil microbial dynamics remain unclear.
Methods:
We investigated the structural and functional responses of rhizosphere versus bulk soil microbiomes associated with Poa alpigena in the Qinghai Lake Basin. Paired soil samples were collected before rainfall and 2 h after a heavy rainfall event and analyzed by shotgun metagenomic DNA sequencing.
Results:
Rainfall triggered compartment-specific shifts in microbial community assembly. In the rhizosphere, rainfall significantly reduced alpha diversity (Chao1 and Richness indices) but enhanced community evenness (Simpson and Shannon indices), whereas bulk soil diversity remained relatively stable. DNA-based functional profiling revealed a short-term shift in the rhizosphere from a pre-rain "carbon-oriented" metabolic potential to increased relative abundance of genes involved in central carbon pathways, amino acid degradation, and chemotaxis post-rainfall. Notably, sequences affiliated with Paraburkholderia were significantly enriched in the nitrogen-limited rhizosphere immediately after rainfall, suggesting a potential link to nitrogen cycling. In contrast, bulk soil communities shifted toward gene categories for labile carbon utilization and bacterial secretion systems. Co-occurrence network analysis indicated that rainfall simplified microbial interactions and weakened the coupling between microbial communities and soil physicochemical properties.
Discussion:
These findings demonstrate that rainfall pulses trigger rapid, niche-dependent changes in soil microbiomes at the DNA level, driven by moisture-mediated shifts in resource availability, and highlight distinct ecological strategies in rhizosphere and bulk soil compartments.
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