• • Proteobacteria dominated nosZ-type denitrifiers at 78.91% relative abundance, indicating a narrow phylum-level diversity that may simplify microbial management strategies for N2O reduction in high-altitude reservoirs.
• • nosZ gene abundance was significantly higher in the Huangshui River basin (165.24×10^5 copies/g) than in the Yellow River mainstem (34.43×10^5 copies/g), a 4.8-fold difference that underscores spatial heterogeneity in denitrification potential.
• • Wet season nosZ gene abundance (128.55×10^5 copies/g) exceeded dry season (61.27×10^5 copies/g) by 2.1-fold (P<0.05), implying seasonal hydrological control on microbial functional capacity.
• • Sediment temperature, pH, total phosphorus, and water total nitrogen collectively explained 59.09% of community variation (individual contributions: 17.14%, 16.89%, 13.83%, 11.23%), providing quantifiable targets for environmental management to optimize N2O reduction.