Infiltration mechanism and source of soil water in alpine meadows based on stable isotope tracing

• Both piston flow and priority flow mode are present. • Piston flow is the primary mode of soil infiltration. • The contribution rate of priority flow mode in higher altitude areas increases. • Precipitation was identified as the primary source of soil water recharge. • Significant variations in soil water recharge among vegetation types and altitudes. To strengthen the management and protection of soil water resources in the Yellow River source area(SRYR), this study conducted a quantitative analysis of the infiltration of soil water in alpine meadows. Meanwhile, the recharge source and mode of soil water in the SRYR were analyzed. The results indicated that both piston flow mode and priority flow mode were present, with the piston flow mode being predominant. The contributions of priority flow mode to deep soil water in different parts of the SRYR were as follows: South > West > North > East. The contributions of piston flow mode to deep soil water were as follows: East > North > West > South. In the heavy ablation period in 2021, precipitation was identified as the primary recharge source of soil water in the SRYR. The contribution rates of precipitation to soil water decreased with the increase in soil depth. The contribution rate of precipitation to soil water on the sunny slope was slightly higher than that on the shady slope. Different vegetation types had obvious effects on the recharge proportions of soil water. In addition, the contribution rates of precipitation to soil water decreased with the increase in altitude, while the contribution rates of ground ice increased with the increase in altitude. This study can provide theoretical support for soil water management and protection in the SRYR, which is conducive to the sustainable development of soil water resources.