Distribution pattern of soil nutrients in different grassland types and soil depths in the eastern Tibetan Plateau

The vertical distributions of carbon,nitrogen and phosphorous in the soil profiles in 7 grassland types in the eastern Tibetan Plateau were investigated.These grassland types were: alpine meadow,alpine shrub meadow,sub-alpine meadow,swamp meadow,desertified steppe,interforest grassland and saline-alkaline meadow.Our results showed that soil organic carbon decreased with soil depth in the 7 different grassland types,and that the cumulative amount of soil organic carbon at 0-15 cm depth in the 7 types was decreased in the following order: interforest grasslandalpine shrub meadowalpine meadowswamp meadowsaline-alkaline meadowsub-alpine meadowdesertified steppe(P0.05).The dynamic of soil total nitrogen in soil depths was similar to that of soil organic carbon,and the cumulative amount of soil total nitrogen at 0-15 cm depth in the investigated types,from highest to lowest,was: swamp meadowinterforest grasslandalpine shrub meadowtestalpine meadowswamp meadowsaline-alkaline meadowdesertified steppesub-alpine meadow(P0.05).Soil total phosphorus showed no obvious pattern in the desertified steppe and interforest grassland types,and the cumulative amount of soil total phosphorus at 0-15 cm depth in the 7 types was decreased in the following order: alpine shrub meadowswamp meadowalpine meadowsaline-alkaline meadowsub-alpine meadowdesertified steppeinterforest grassland(P0.05).Soil nutrient distribution varies when soil depth increases in different grassland types.Soil organic carbon was significantly correlated with soil total nitrogen in all grassland types except the swamp meadow.