highly significantP < 0.001
Statistical analysis using the Wilcoxon test confirmed significant differences in alpha diversity indices among the regions, with the Yangtze region showing highly significant differences in indices compared to both the Northwest Inland (Simpson: P < 0.001; Shannon: P < 0.001; ACE: P < 0.01; Chao1: P < 0.01) and Yellow River Basin (Simpson: P < 0.01; Shannon: P < 0.01; ACE: P < 0.05; Chao1: P < 0.05).