Stratifying soils into pedogenically similar categories for modeling forest soil carbon

Most forest ecosystem carbon (C) models are designed to estimate total ecosystem C including soil C stocks and fluxes. Stratification by tree species is often used in these models to reduce uncertainty, but the potential of stratification by soil taxon has received little attention. This potential can be realized only if meaningful modeling strata are identified. Therefore, the objectives of this study were: (a) to distinguish strata of soil C modeling cateogories (SCMC) on the basis of soil C stocks of taxonomic categories that are characterized by similar pedogenic processes important to C dynamics, and (b) to review the literature to test the robustness of the SCMC scheme. Carbon stocks of 1383 forest soil pedons were analyzed by multiple means comparisons for soil orders and by orthogonal contrasts between pedologically related sets of subgroups within soil orders. Eleven SCMCs were distinguished with mean total C stocks varying from 325 ± 37.2 t ha -1 for the gleyed Cryosol SCMC to 94 ± 3.9 t ha -1 for the Brunisolic Gray Luvisol SCMC. A review of the literature relevant to each SCMC demonstrated that there is a scientific basis for using these strata to model forest soil C dynamics. Key words: Forest soil, carbon, modeling, pedology, genesis