Isotope Composition of Carbon of Plants and Organic Matter in Burozems of the Southern Vitim Plateau

The isotopic composition of vegetation and organic matter of permafrost burozems in the south of the Vitim Plateau is analyzed. The soil profile is characterized by a pronounced uneven carbon distribution. Carbon reserves are mainly concentrated in the humus-accumulative horizon and sharply decrease down the soil profile. Vegetation on burozems is assigned to the C-3 type of photosynthesis. The aboveground parts of legumes, forbs, and semishrubs are somewhat depleted of the 13 C isotope as compared to the underground organs. The 13 C content in branches, needles, and leaves of trees differs slightly. The isotope composition of carbon in the upper horizons of soils depends on the type of phytocenosis and its values are close to δ 13 C in dominant plants. Fractions of carbon isotope are clearly differentiated with the depth in the soil profile. The isotope composition of carbon of humic acids from the humus-accumulative horizon and from soils of cryogenic cracks slightly differs. The composition of stable carbon isotopes of humic acids in the soil profile remains approximately the same. These data testify to the similarity of the formation processes of humic acids in the upper soil layers and in humus pockets.