4 Sukachev's Laboratory of the Institute of Evolution and Ecology Problems, Leninsky Prospect 33, 117071 Moscow, Russia; 5 V.N. Sukachev Institute of Forests, Akademgorodok, 660036 Krasnoyarsk, Russia; 6 present address: HSSE-AG National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616 Singapore ABSTRACT We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (ex-cluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia. Carbon inven-tories over 0–30 cm depth range widely from 1.71 to 7.05 kg m −2 . While an effect of changing climate or vegetation along the transect cannot be ruled out, the observed differences in SOC in-ventories are largely the result of variations in mineral soil texture, with inventories in fine-textured soils being approximately double those in coarse-textured soils. The δ 13 C values of SOC in the 0– 5 cm interval ranged from −26.3 to −28.0‰, with δ 13 C values for the 5–30 cm interval being 0.9 ± 0.8‰ (1σ) enriched in 13 C relative to the 0–5 cm samples. The average δ 13 C value for the 0–5 cm interval for all samples was −27.1 ± 0.6‰ (1σ) and for the full 0–30 cm interval the average was −26.5 ± 0.5‰ (1σ). In general, δ 13 C values were higher in coarse-textured soils and lower in fine-textured soils. The results of detailed sampling of soils in Pinus sylvestris forest growing on sand near the Zotino flux tower suggest an SOC inventory in these soils of 2.22 ± 0.35 kg m −2 over 30 cm and an average δ 13 C value of −26.3 ± 0.2‰ over the 0–5 cm depth interval and −25.9 ± 0.3‰ over 0–30 cm. Recent burning had no effect on SOC inventories, but clearing has led to an average 25% decrease on SOC inventories from 0–30 cm over 12 yr. Neither burning nor clearing had a discernible effect on the δ 13 C value of SOC.