Community structure of Anthoxanthum glabrum (Trin.) Veldkamp in the Sanjiangyuan area and its response to soil factors

To investigate the characteristics of Anthoxanthum glabrum (Trin.) Veldkamp plant communities and their responses to soil factors in the Sanjiangyuan region of Guoluo Tibetan Autonomous Prefecture, Qinghai Province, five representative A. glabrum-dominated communities were selected for this study. Species composition, importance values, diversity indices, aboveground biomass, and soil physicochemical properties were analyzed across the different plots. In addition, correlation and redundancy analyses were conducted to explore the relationships between community structure and soil environmental variables. A total of 18 plant species were recorded across the five communities, belonging to 17 genera and 12 families. Significant differences were observed in community diversity indices and aboveground biomass. The Margalef richness index, Simpson diversity index, Shannon-Wiener index, and Pielou evenness index were highest in plot 5 and lowest in plot 1, with statistically significant differences among the plots. Aboveground biomass was significantly higher in plot 2 compared to the other plots, reaching a maximum of 1368 g·m⁻². Soil environmental factors showed considerable heterogeneity among the different A. glabrum communities. Plots 2 and 3 had significantly higher nutrient content than the other plots. Correlation analysis revealed 53 statistically significant, highly significant, or extremely significant relationships among the 15 diversity indices and biotic or abiotic soil variables. Redundancy analysis indicated that soil moisture and available phosphorus were the primary soil factors influencing community structure, accounting for 85.5 percent and 8.2 percent of the explained variance, respectively. Further analysis at the taxonomic level showed that soil organic matter and total phosphorus were strongly associated with the number of families, genera, and species within the communities. Their contribution rates were 68.9 percent and 13.2 percent, respectively. These results indicate clear differences in A. glabrum community composition among plots, and demonstrate that soil factors, particularly soil moisture and organic matter, play a key role in shaping community structure at the local scale.