Predicting carbon storage in tundra soils of arctic Alaska

The distribution of soil organic carbon (SOC) was determined in 60 pedons from northern Alaska by horizon, within the seasonal thaw layer, and to a depth of 1 m. Concentration of SOC, bulk density, and SOC density were remarkably uniform for a given genetic horizon and had low standard errors. With increasing degree of decomposition, the bulk density increased, the concentration of SOC decreased, and the soil horizon C density increased in organic horizons. For mineral horizons, gleying is accompanied by an increase in C density, which is due to the effect of saturation on limiting decomposition of organic matter. Cryoturbation of organic or mineral minerals into the subsoil results in an increase in C density primarily from an increase in bulk density because of compaction from the overlying layers and more closely packed soil particles from frost churning. Estimated SOC storage for individual horizons and for the seasonal thaw layer were highly correlated (p<0.01) with measured values from an independent data set for the same region published by other investigators. Equations relating C density to percentage of visible ice enable prediction of SOC in the near-surface permafrost. The equations generated by this study will be useful in preparing a detailed soil C map of the arctic regions.