Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2003
Publication Date: 7/1/2003
Citation: Galbraith, J.M., Kleinman, P.J., Bryant, R.B. 2003. Sources of uncertainty affecting soil organic carbon estimates in northern new york. Soil Science Society of America Journal. 67:1206-1212. Interpretive Summary: Concern over the build up of greenhouse gases in the atmosphere and related global climate change has prompted numerous modeling efforts aimed at quantifying global carbon cycling. Such efforts have been limited by the quality of the data on which they were built, highlighted by the fact that roughly one quarter of carbon sequestered by soil each year remains unaccounted for in existing global carbon models. One source of these discrepancies could be the accuracy of the soil surveys used to estimate soil organic carbon stores. Possibly, modelers would be required to use detailed local soil surveys, rather than rely upon more generalized, regional surveys, leading to great demands on computational capacity and resource expenditures. In this study, the effect of a wide range of soil surveys, from fine scale (1:15,840) to regional (1:7,500,000), on estimating regional soil organic carbon stores was examined. Results indicate that regional soil surveys can provide sufficiently reliable information to accurately estimate regional soil organic carbon stores.
Technical Abstract: Estimations of regional soil organic carbon (SOC) stores are sensitive to SOC data, extrapolation methods, series composition, and generalization accuracy of small-scale maps used for regional SOC estimation. A set of SOC samples from the surface to one meter (or bedrock) was composed for soil series occurring within the boundaries of four atlas sheets from the Oswego County Soil Survey in the Tughill Plateau (MLRA 141) of New York. Atlas sheet boundaries were used to define the areas for comparison between maps of five different scales ranging from 1:15,840 to 1:7,500,000. Maps were digitized and used with the SOC data set to calculate and compare SOC estimates across map scales. The most detailed soil map (Oswego County Soil Survey) yielded an SOC estimate (weighted by land extent) of 16.7 Kg m-2 in the Tughill. The 1:250,000 scale STATSGO Soil Map and 1:500,000 scale New York State General soil maps overestimated SOC by approximately four to five percent, while the 1:62,500 scale Oswego County General Soil Map and the 1:750,000 scale MLRA Soil Map produced similar estimated SOC stores as the reference scale. Differences in SOC between map scales were the result of differences in soil series composition due to correlation decisions or to generalization inaccuracy. General soil maps that accurately report the extent of water and soils representing the highest and lowest extremes of SOC contents can be used to make reliable estimates of SOC.