Abstract: The distribution of inorganic carbon in soil profile is crucial for assessing regional soil inorganic carbon storage, terrestrial carbon cycle, and global climate change. In this paper, the pH value, carbonate content, and its δ¹³C and δ¹⁸O values in five soil profiles under different vegetation types in the Loess Plateau were measured, aimed to explore the effects of vegetation type on the distribution and isotopic composition of inorganic carbon in the soil profiles. In the five 0-130 cm soil profiles, carbonate content varied from 5.7% to 14.1%, and its average value was in the sequence of wasteland > grassland > broadleaf forestland > shrub forestland > coniferous forestland. As affected by the parent material loess, the soil was weakly alkaline, with pH value 7-8. The δ¹³C value of the soil carbonate varied from -6.2‰ to -1.8‰, with the order of wasteland > shrub forestland > coniferous forestland > grassland > broadleaf forestland. Vegetation type affected the δ¹³C value of the soil carbonate mainly through the input of organic carbon. The δ¹⁸O value of the carbonate in the soil profiles under different vegetation types had significant distinction, which was possibly affected by the soil physical properties such as porosity and humidity. In the Loess Plateau, there was a significant difference in the vertical distribution of soil inorganic carbon content and its δ¹³C and δ¹⁸O values under different vegetation types, and thus, the vegetation type change during vegetation succession could affect the storage of soil inorganic carbon and the process of regional carbon cycle.

Key words: cotton stalk biochar, Biolog, DGGE, rhizosphere, continuous cropping cotton.