Threshold effects of soil pH regulate the biogeography of bacterial communities in inland wetlands across eastern China

Abstract

Biogeographic patterns of microbial communities in wetland soils at broad scales remain underexplored compared to those in well-drained soils, particularly regarding abundant and rare taxa. Here, we investigated the ecological distributions and assembly mechanisms of abundant and rare bacterial sub-communities and explored their underlying environmental drivers in inland wetland soils across eastern China. Both bacterial sub-communities exhibited significant distance-decay relationships (DDR), with a stronger DDR observed for abundant sub-communities due to more pronounced environmental filtering and dispersal limitation. Deterministic processes predominantly governed bacterial communities (62%‒97%), while stochasticity played a larger role in rare sub-communities (38%) compared to abundant ones (4.0%). Soil pH emerged as a dominant factor influencing bacterial communities and mediated the assembly of both sub-communities. The diversity of overall and rare taxa increased with pH and peaked at pH of 8.31, followed by an abrupt decline, suggesting a threshold effect on their ecological distributions. When pH exceeded 8.31, bacterial communities rapidly converged to more deterministic assemblages (especially for abundant taxa), with decreased species coexistence and increased negative cohesion (i.e., reflecting the degree of competition), suggesting intensified niche-based exclusion among bacterial communities. Collectively, this broad-scale study provides new insights into pH-related rules governing wetland bacterial biospheres and underscores the distinct biogeographic patterns between abundant and rare bacteria. The abrupt threshold of soil bacteria identified can inform effective adaptation and conservation efforts to sustain wetland ecosystem functioning.

Graphical abstract

Keywords

pH threshold / microbial biogeography / community assembly / deterministic process / rare biosphere

Highlight

	● Distinct biogeographic patterns of bacterial abundant and rare taxa were detected.
	● Determinism governed bacterial community assemblages especially for abundant one.
	● Soil pH threshold effects imposed strong effects on shaping bacterial distribution.
	● Niche-based exclusion (overlap) of bacterial communities intensified at pH > 8.31.

References

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