Study on the vertical distribution of soil organic carbon density in the Tibetan Plateau

Soil organic carbon, particularly high altitude soils, may have important effects on the global carbon cycle and global warming. A quantitative study on Tibetan Plateau soils was carried out to determine the vertical distribution of soil organic carbon density in three layers (0~20 cm, 20~50 cm and 50~100 cm) of 28 soils and 14 ecosystem types. The average soil organic carbon densities in the three layers were (6.16±1.08) kg·m-2, (5.06±0.85) kg·m-2, and (5.30±0.82) kg·m-2. The soil organic carbon density of dark brown earth and bog soil were highest in the 0~100 cm depth of soil among 28 soil types, while the carbon density of alpine desert soil and subalpine desert soil were significantly lower than the others. The average soil organic carbon density in the three layers among 14 ecosystems were (7.47±1.38) kg · m-2,(6.07±1.24) kg · m-2,and (6.46±1.16) kg · m-2. The soil organic carbon densities of bog meadow and conifer forest were not only higher than the average level of the study area, but also significantly higher than the others. However, the soil organic carbon density of alpine grassland, subalpine grassland, temperate desert and alpine desert were about 3.0 kg·m-2, significantly lower than the other ecosystems. This study not only indicated that soil organic carbon density in the Tibetan Plateau varied significantly among the 28 typical soil types and 14 ecosystems, but also showed a zonal distribution of ecosystem and the soil in the study area, which could provide information for models of the soil organic carbon cycle, and on the response of soil organic carbon in the Tibetan Plateau to global climate change.