Select from available options to download raster data in GeoTIFF format. The full raster extent can be subset in one of three ways from the Extent button on the map.
When uploading a file or selecting an ecoregion the raster data will be masked outside of the polygon boundary.
Uncertainties that exist in the data products are the results of the estimation and projection methods used for the assessment. Major sources of uncertainties for baseline (1992-2005) data products include assumptions made in structure and parameterization of specific methods and models used in the assessment, relations and integration of these methods and models, and input data availability and quality. The use of land- and climate-change scenarios in the assessment, as part of the carbon modeling, is an additional source of uncertainty for the projected (2006-2050) data products.
Because of the specific methods used in the assessment, the uncertainties are distributed both in temporal and spatial dimensions and they vary by product, location, and specific use. Along the temporal dimensions, mean values of baseline and projection years should be used instead of any given individual years. Along the spatial dimensions, data aggregated to the scale of ecoregions should be used instead of the individual pixels or over relatively small areas of the maps. In addition, the available multiple models and scenarios provide users with ranges of values for a given estimate, which may be used as a means of quantifying the spread of uncertainties.
Soil organic carbon (SOC) is the carbon held within soil organic constituents (i.e., products produced as dead plants and animals decompose and the soil microbial biomass). Only SOC in the top 20-cm soil layer was reported in this assessment. For the western United States, average soil carbon stock during the baseline period (2001 – 2005) was estimated to be between 4778-5,919 Tg C, which included 2242- 2613, 2034-2531, 452-556 Tg C for forest, shrub/grass lands, and agricultural land, respectively. Assessment indicates that for the scenario period (2006-2050), SOC will increase by about 44%, ranging from 4682-8575 TgC considering different scenarios of LULCC, climate, and models.
Zhu, Zhiliang, ed., Bergamaschi, Brian, Bernknopf, Richard, Clow, David, Dye, Dennis, Faulkner, Stephen, Forney, William, Gleason, Robert, Hawbaker, Todd, Liu, Jinxun, Liu, Shuguang, Prisley, Stephen, Reed, Bradley, Reeves, Matthew, Rollins, Matthew, Sleeter, Benjamin, Sohl, Terry, Stackpoole, Sarah, Stehman, Stephen, Striegl, Robert, Wein, Anne, and Zhu, Zhiliang, 2010, A method for assessing carbon stocks, carbon sequestration, and greenhouse-gas fluxes in ecosystems of the United States under present conditions and future scenarios: U.S. Geological Survey Scientific Investigations Report 2010–5233, 188 p. (Available from USGS).
The temporal and spatial dynamics of SOC were estimated using the USGS General Ensemble Biogeochemical Modeling System (GEMS), which involved three models (Paint-By-Number (PBN) model, CENTURY, and EDCM), under three land use and land cover change (LULCC) scenarios developed in accordance with storylines A1B, A2, or B1 from the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC–SRES) and climate-change projections by three general circulation models (GCMs). Soil organic carbon was initialized using data from the Soil Survey Geographic Database (SSURGO). SOC dynamics in five pools (i.e., structural, metabolic, fast, slow, and passive) were simulated considering LULCC, disturbances, and climate conditions. PBN does not track SOC change over time.