The Unified North American Soil Map and its implication on the soil organic carbon stock in North America

摘要

The Unified North American Soil Map (UNASM) was developed to provide moreaccurate regional soil information for terrestrial biosphere modeling. TheUNASM combines information from state-of-the-art US STATSGO2 and SoilLandscape of Canada (SLCs) databases. The area not covered by these datasetsis filled by using the Harmonized World Soil Database version 1.21 (HWSD1.21).The UNASM contains maximum soil depth derived from the data source as wellas seven soil attributes (including sand, silt, and clay content, gravelcontent, organic carbon content, pH, and bulk density) for the topsoillayer (0–30 cm) and the subsoil layer (30–100 cm), respectively, of thespatial resolution of 0.25 degrees in latitude and longitude. There arepronounced differences in the spatial distributions of soil properties andsoil organic carbon between UNASM and HWSD, but the UNASM overall providesmore detailed and higher-quality information particularly in Alaska andcentral Canada. To provide more accurate and up-to-date estimate of soilorganic carbon stock in North America, we incorporated Northern CircumpolarSoil Carbon Database (NCSCD) into the UNASM. The estimate of total soilorganic carbon mass in the upper 100 cm soil profile based on the improvedUNASM is 365.96 Pg, of which 23.1% is under trees, 14.1% is inshrubland, and 4.6% is in grassland and cropland. This UNASM data willprovide a resource for use in terrestrial ecosystem modeling both for inputof soil characteristics and for benchmarking model output.