Abstract: This study aimed to explore the differences in soil carbon, soil nutrients and soluble organic carbon, and their correlation with soil nutrient levels in 4 different types of alpine grassland in Qinghai province. Measurements made included: soil organic carbon, total nitrogen, total phosphorus, total potassium, and soluble organic carbon in the 0-10 cm and 10-20 cm soil layers. Correlations between soluble organic carbon and organic carbon and nutrients were determined. The results showed that the ranking of the grassland types for contents of total nitrogen, organic carbon and soluble organic carbon in tested soil layers was alpine meadow>alpine meadow steppe>alpine steppe>alpine desert, with the differences being significant (P<0.05). As expected, the soil total nitrogen and organic carbon content tended to decrease with increasing soil depth. The soluble organic carbon aromaticity and humus indexes for the different alpine grassland types had the same rankings as for total nitrogen and organic carbon, above. There was a significant positive correlation between soluble organic carbon and soil total nitrogen and organic carbon (P<0.05). It was concluded that the contents of organic carbon, total nitrogen and soluble organic carbon in alpine meadow and alpine meadow steppe were high, and the structure of organic matter was complex. The soluble organic carbon aromaticity and humus indices were, to a certain degree, indicative of soil nutrient status.

Key words: alpine grassland, soil organic carbon, soil nutrient, soil soluble organic carbon