Alpine meadow patches unevenly regulate runoff and sediment yield generation on the Qinghai-Tibetan Plateau

Meadow patches are caused by the fragmentation and disappearance of mattic epipedons, and can serve as evidence of degradation. This is a gradual decline in meadow patch coverage, which can result in soil and surface water loss due to increased bare soil surface. However, little is known about how the loss of mattic epipedons alters soil erosion processes in alpine regions. This study sheds light on this topic by conducting simulated rainfall experiments with different rainfall intensities to assess runoff and sediment generation. We selected representative degraded alpine meadows on the eastern Qinghai-Tibetan Plateau in China. The observed temporal variations of runoff and soil loss rates were explained by the presence of two stages of meadow patch coverage decline: an increasing and a relatively stable stage. Compared to 30% and 60% meadow patch coverage, 90% meadow patch coverage displayed an extended increasing stage with delayed entrance into the stable stage during the rainfall period. The runoff coefficients were significantly higher in 90% and 30% meadow patch coverage than in 60%. The sediment concentrations were significantly lower in 90% and 60% meadow patch coverage than in 30%. It is worth stressing that 90% meadow patch coverage could prompt more rainfall flowing as runoff and reduce sediment under different rainfall intensities. The complex mosaic-pattern formed by meadow and bald patches changed the hydrological response of the soil, decreasing runoff coefficient in 60% meadow patch coverage. The destruction, reduction or even disappearance of some mattic epipedons led to a higher sediment concentration in 30% meadow patch coverage. The meadow patch coverage exerted a greater influence on sediment yield than on runoff volume, although it was generally affected by rainfall intensity. Our findings highlight the importance of maintaining runoff and reducing sediment through the presence of mattic epipedons. Mattic epipedons appear as an effective soil erosion control feature, and this study offers a theoretical guidance for planning adaptive management strategies for degraded alpine meadows on the Qinghai-Tibetan Plateau.