Field Simulation of Runoff and Sand Production on Degraded and Revegetated Slopes in Alpine Meadows Under Rainfall Conditions

Abstract

[Objective] The Qinghai-Tibetan Plateau is an important ecological barrier in China, and alpine meadows are an important part of it, and the function of soil and water conservation is an important ecological service function of alpine meadows. Therefore, it is of great significance to carry out the study of soil erosion process in alpine meadows on the Tibetan Plateau to reduce anthropogenic disturbance of soil erosion and to safeguard the ecological security of the southwest region. [Methods] In this study, five different types of slopes, namely, undegraded, mildly degraded, moderately degraded, bare slopes and artificially restored slopes in alpine meadows of the Tibetan Plateau, were selected to analyze the process of flow and sand production on degraded and restored slopes under different rainfall intensities, and to reveal the relationship between the erosion mechanism and water-sand relationship between degraded slopes and restored slopes with artificial vegetation through the simulated rainfall test in the field. [Results] (1) The initial flow production time is relatively short on the undegraded slopes of alpine meadows and the restored slopes with artificial vegetation because of their dense root system, and the water infiltration ability is relatively weak; while on the mildly degraded slopes, the lateral flow and vertical infiltration ability are relatively strong, and the initial flow production time is relatively long. (2) Under regular rainfall conditions (30 and 60 mm/h), the flow rate of mildly degraded slopes is the smallest, and the flow reduction benefit is the highest, reaching 77.13%, the flow rate of artificially restored slopes is close to that of undegraded slopes and is slightly higher than that of mildly degraded slopes; the cumulative flow rate of bare soil slopes is the largest, and it is significantly higher than other slopes; the flow rate of undegraded slopes under extreme rainfall conditions (90 mm/h) is surging, only lower than that of bare slopes and significantly higher than other slopes. Under extreme rainfall conditions (90 mm/h), the flow rate of undegraded slopes increased, which was only lower than that of bare slopes and significantly higher than that of artificially restored slopes. (3) Under regular rainfall conditions (30 and 60 mm/h), the sand reduction benefit of the artificially restored vegetated slopes was the highest, reaching 81.97% and 89.82%, followed by the undegraded slopes, and with the increase of the degradation degree of the vegetation, the sand reduction benefit was gradually reduced; however, under extreme rainfall conditions, the sand reduction benefit of the artificially restored vegetation and the undegraded slopes was almost the same, and the sand production of the moderately degraded slopes was higher than the undegraded slopes, which is significantly higher than the other slopes. However, under extreme rainfall conditions, the sand reduction benefits of artificially restored vegetation and undegraded slopes are almost the same, while the sand production of moderately degraded slopes is 4.59 times of that of undegraded slopes. [Conclusion] The results of these studies can provide important scientific basis for vegetation restoration and ecological security in alpine meadow area.

Keywords

• alpine meadow
• degraded meadow
• water and soil loss erosion
• benefit of runoff and sediment reduction