Spatial distribution of soil carbon in Southern New England hardwood forest landscapes

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Date of Original Version



Understanding soil organic C (SOC) spatial variability is critical when developing C budgets, explaining the cause and effects of climate change, and for basic ecosystem characterization. We investigated delineations of four soil series to elucidate the factors that affect the size, distribution, and variability of SOC pools from horizon to landscape scales. These soils, classified as Udipsamments, Dystrudepts, Endoaquepts, and Haplosaprists, were sampled along random transects to a depth of 1 m. In very poorly and poorly drained soils 75 and 45% of total SOC was found below 30 cm, respectively. In contrast, only 30% of the total SOC could be accounted for below 30 cm in the well and excessively drained soils. Soils formed in outwash and young alluvium sequestered a greater portion of total SOC within the subsoil, while soils formed in loess held approximately 70% of the SOC within O and A horizons. Total SOC contents among the four soil types differed significantly (p < 0.001), with the wetter soils having greater accumulations of C. Soil C pools ranged from 110 Mg C ha-1 in the excessively drained Psamments (double the mean national value) to 586 Mg C ha-1 in the very poorly drained Saprists (30-60% lower than the mean national value). The two-fold differences between our data and the national averages support the need for regional assessments of soil C pools. Based on the coefficient of variation (CV) values, there appears to be nearly as much variability in the SOC pool within a delineation (CVs ranged 9 to 30%) as among delineations (CVs ranged from 15 to 31%) for the same soil type. Since significant differences were found for total SOC among delineations of the same soil type, we concluded that sampling from a significant number of delineations of the same series will provide a more accurate representation of SOC for scaling to the landscape or region than sampling at multiple locations within a single representative delineation.

Publication Title, e.g., Journal

Soil Science Society of America Journal