Abstract: Saline vegetation in arid area is widely distributed,and the plant species are numerous,which plays an important role in the ecosystem carbon balance and regional climate regulation.In this paper,the field investigation in the Dabancheng saline lake area in Xinjiang and the indoor analysis were carried out so as to study the characteristics of carbon density distribution of saline vegetation and soil in this arid area.The results showed that the soil organic carbon density decreased with the increase of soil depth,it varied in a range of 7.55-15.75 kg·m^-2 within 0-100 cm soil layer,and its average value was 12.54 kg·m^-2 and accounted for 97.84% of the total organic carbon density of plant community and soil.Lycium ruthenicum and Halimodendron halodendron are the dominant species in the halophyte communities,their average aboveground biomass was 261.38 g·m^-2 and accounted for 70.49% of the total biomass.The biomass of herbaceous plant community was 109.45 g·m^-2.The aboveground biomasses of shrub and herb layers were significantly higher than the biomasses of their litter layers (84.81±9.22) and (79.76±8.61) g·m^-2.The underground biomass of halophytes decreased with the increase of soil depth,and it in 0-100 cm soil layer was 77.74 g·m^-2.The carbon density of total biomass of halophytes was 276.48 g·m^-2,in which the aboveground,litter and underground biomasses accounted for 62.09%,25.75% and 25.75% of the total respectively.The carbon density of aboveground vegetation and litters was significantly higher than that of herbaceous plants,that of root biomass varies and its 96.55% concentrated in 0-50 cm soil layer.The average carbon content of aboveground,underground and litter of halophytes was 43.09%,which was 13.80% higher than the value estimated with empirical coefficient (50%) and produced high deviation in estimating vegetation carbon reserve.

Key words: soil organic carbon, soil carbon density, biological carbon density, ecosystem, distribution pattern, Saline lake, arid areas