Carbon Storage and Distribution in Tundra Soils of Arctic Alaska, U.S.A.

Tundra soil carbon stores ranged from a low of 16 kg C m-3 for a northern foothills ridge top site to a high of 94 kg C m-3 for a Barrow coastal plain tundra. Relatively low carbon stores were found in riparian shrubland, barren mountain slope, and alpine slope soils (3, 4 and 10 kg C m-3, respectively). Coastal plain and foothills tundra soils averaged 62 and 44 kg C m-3, respectively. Active layer to permafrost partitioning of carbon stores varied, but when the carbon stores of the permafrost (to 1 m) were considered along with those of the active layer, carbon store estimates for the tundra are nearly doubled. Cryoturbation played a key role in the distribution of soil carbon stocks. Carbon stores over the pattern cycle of three coastal plain polygon types were found to be similar (59-60 kg C m-3). However, the carbon stores of coastal plain thaw lake basin soils ranged widely from 16 to 64 kg C m-3. In the foothills, carbon stores increased from ridge top to down-slope positions, and increased or stayed nearly constant from midslope to watertrack positions. On the average, the largest carbon stores were in the Cf, Oa, and Bg/Oa soil genetic horizons with average stores to 1 m of 15, 13, and 13 kg C m-2, respectively. Carbon stores for the Kuparuk River drainage were calculated for the pedon (1 m) and for the active layer only, the results were 2.5 and 1.4 times higher, respectively, than if generalized tundra carbon stores from the literature were used in the calculation. The results of this study indicate that the Arctic terrestrial carbon pool size estimates that have been used recently could be low by a factor of 2 or more if the lower soil horizon stores are ignored.