Wind Tunnel Simulation and Assessment of Soil Conservation of Alpine Grassland in Qinghai,Tibet Plateau

The soil conservation of alpine grassland is one of the important functions for environ,mental protection in Qinghai,Tibet Plateau.Aimed to study on impact of human activities on services of soil conservation,this paper simulated soil erosion changes under different disturbed patterns of human activities by using the wind tunnel laboratory.Three types of grassland were selected which included alpine meadow,alpine steppe meadow and alpine steppe and the erosion rate as indicator measure function of soil conservation.In general,the greater the soil erosion is,the lower the soil conservation function is.The results showed that the soil erosion rate of three grassland samples increased with wind velocity under different treatments but the increment of erosion rate varied greatly.The erosion rate change of the alpine meadow was the same as that of the alpine steppe when the surface vegetation was cut,and compared with the original status both of them changed a little.And when the root system was broken the erosion rate ranged from high to low in turn of alpine meadow,alpine steppe meadow and alpine steppe.So the data suggested that the function of soil conservation for three types of grassland should be alpine meadowalpine steppe meadowalpine steppe.The organic matter and nutrient content were analyzed before and after the aeolian erosion simulation and the decrease of all nutrients were obvious in particular the K2O.The economic values of soil conservation were estimated that included the values of organic carbon fixation,nutrient detention and decrease of soil deposits.The results indicated that the value of nutrient detention is the highest and the economic value of soil deposits decrease is the lowest.The total economic value per unit area varied in turn of alpine steppe meadow,alpine meadow and alpine steppe.