keystone species within surface-dwelling microbial aggregates
The surface soil horizon, functioning as the biogeochemical nexus in paddy ecosystems, harbors architecturally complex microbial consortia where abundant and rare taxa exhibit functional redundancy. While these aggregates drive critical nutrient cycling processes, the mechanistic partitioning of ecological roles between abundant and rare subcommunities remains obscured, limiting the development of microbiota-targeted agricultural optimization strategies. To experimentally dissect their functional hierarchies, we developed a controlled culturing system (26 °C, 12-h light/dark cycle, 10,000–12,000 lux; nutrient supply: 10% soil leachate + 0.5% mineral solution) to selectively suppress rare taxa while preserving the abundant taxa. Systematic functional partitioning revealed three cardinal determinants of abundant subcommunity ecological predominance: (1) abundant taxa account for >50% of the microbial diversity, (2) dominate community assembly processes, and (3) exert greater influence on carbon, nitrogen, and sulfur cycling compared to rare taxa. Our approach establishes causal relationships beyond bioinformatic speculation, providing a functional disentanglement framework that redefines abundant taxa as keystone engineers of aggregate stability and functionality. This conceptual shift holds significant promise for the advancement of precision agriculture and the development of more sustainable nutrient management approaches.