Characteristics of soil water percolation and dissolved organic carbon leaching and their response to long-term fencing in an alpine meadow on the Tibetan Plateau

Fencing is an important method for restoring and reconstructing degraded grasslands on the Tibetan Plateau. Understanding the characteristics of soil water percolation and soil dissolved organic carbon (DOC) leaching and their response to long-term fencing (10 years) could provide a scientific basis for the management of soil water resources and carbon sinks in alpine grasslands. In this study, grazing plots and plots fenced for 10 years were selected in an alpine meadow, and soil bulk density, soil organic carbon (SOC) density, vegetative carbon (VC) density, soil water percolation and DOC leaching were monitored regularly in the two treatments. The results were as follows: (1) Long-term fencing reduced the soil bulk density and improved carbon sequestration in the alpine meadow. The soil bulk density at a depth of 0–20 cm in the fenced plots was significantly lower than that of the grazing plots (p < 0.05), and SOC density and VC density at a depth of 0–40 cm were higher than those of the grazing plots to a different degree. (2) During the non-frozen period (from May to September), total soil water leakage at a depth of 40 cm in the grazing plots was 9.6 mm, which accounted for 2.2% of the total rainfall in this period. After fencing for 10 years, soil water leakage was increased by 53.1%. (3) From May to September, total DOC leaching from the grazing plots was 34.6 gC m−2, and total DOC leaching from the fenced plots was increased by 55.5% compared to the grazing plots. Our results demonstrated obvious soil water percolation and DOC leaching in the alpine meadow. The DOC entered into the groundwater system with the percolation water and finally flowed into lakes and rivers, which represents an important soil carbon loss pathway in alpine meadows.