Methods The study areas are located in the mountain meadow in Guanyuan City, Ya’an City, Liangshan Prefecture of Sichuan Province, China. Plant populations were recorded according to species, number, coverage, meantime, and soil samples (0-10, 10-20, 20-30 cm) were collected and analyzed for SOC content, the carbon content of root, soil pH value, and soil total nitrogen. The diversity indices for plant community diversity (Shannon-? Wiener index) was also calculated to analyze their relationships with SOC content among different climate types.

Important findings Results showed that: (1) SOC in three sites was significantly different and was in the order of Ya’an > Liangshan Prefecture > Guanyuan, and decreased with soil depth. (2) The percentage of SOC content in each vertical layer out of total SOC was lower in the 0-10 cm layer at Ya’an site than at the other two sites, but was higher than the other two sites in the 10-20 cm layer. (3) At Guanyuan site, SOC content in 10-20 cm was significantly positively correlated with plant species richness index and SOC content in 20-30 cm was negatively correlated with plant Shannon-Winner index, while soil pH value and soil total nitrogen were significantly positively correlated with SOC content in each layer. At Ya’an site, SOC content in each layer only had positive correlation with soil pH value, but not with other examined factors. At Liangshan Prefecture site, SOC content in each layer only had positive correlation with soil nitrogen content, but not with other examined factors. (4) Principal component analysis showed that, at Guanyuan, Ya’an and Liangshan Prefecture sites, the total contents of SOC were dominantly affected by climate, followed by vegetation type.