Site-Specific Soil-Carbon (S3C) Database for Mineral Soils of the Mississippi River Basin, USA

The S3C database is a pedon[1]-based, site-specific, soil-organic-carbon (SOC)
database for mineral soils of the Mississippi River basin. The included
soil-carbon and related ancillary data are for 9,215 pedons that were described
and sampled by various agencies between 1928 and 1995 and represent 2,719 of
the 22,517 officially described soil series catalogued by the U.S. Department
of Agriculture, Natural Resources Conservation Service, National Soil Survey
Center, Lincoln, NE (Soil Survey Staff, 2003). The S3C database was originally
developed for use in USGS terrestrial-carbon cycling studies in the Mississippi
River basin (Sundquist and others, 1998) as part of the U.S. Global Change
Research Program, Global Carbon Cycle Program Element
("http://www.usgcrp.gov/usgcrp/ProgramElements/carbon.htm"). The USGS studies
were designed to characterize systems across spatial scales ranging from
hillslopes to small watersheds to the large-river systems that comprise the
Mississippi River basin. These studies included (1) measurement of SOC
erosion, deposition, and transformation at the field scale, (2) measurement and
modelling of SOC and sediment transport at the small-watershed scale, and (3)
measurement, modelling, and statistical analysis of environmental controls on
the geographic distribution of SOC at the large-basin scale.

The S3C database includes both pedon-level and horizon-level data with values
for organic carbon, carbonate, bulk density, particle size (total sand, silt,
and clay), texture class, pH, water content, and soil volume (particles <2 mm
diameter). SOC mass storage (kg m-2) was calculated for each soil horizon and,
at the pedon level, for the following standard depth intervals?0 to10, 0 to 20,
0 to 50, 0 to 100, 10 to 20, 20 to 50, and 50 to 100 centimeters.
Mass-weighted mean values for carbonate, bulk density, particle size and
texture class, pH, water content, and soil volume were also calculated for the
standard intervals.

The horizon-level data are provided for those interested in the study of
site-specific carbon-cycling processes. The pedon-level data are provided for
those interested in regional analysis and modelling.

The S3C database was compiled from the following sources:

1. U.S. Department of Agriculture, Natural Resources Conservation Service,
National Soil Characterization Database (U.S. Department of Agriculture,
2001?7,821 pedons, 1938 to 1995, geographic coverage?basinwide);

2. two surveys of high-elevation soils in the Southern Blue Ridge (Fenneman,
1938) physiographic province (Daniels and others, 1987a, b?8 pedons, Graham
County, North Carolina; Feldman, 1989, 2000, Feldman and others, 1991a, b?37
pedons, Swain and Yancey Counties, North Carolina, Sevier County, Tennessee,
Grayson and Smyth Counties, Virginia);

3. University of Arkansas, Soil Characterization Database (University of
Arkansas, 2000?495 pedons, 1955 to 1992, Arkansas statewide);

4. University of Illinois, Soil Characterization Database (University of
Illinois, 2001?778 pedons, 1928 to 1990, Illinois statewide); and

5. a survey of flood-plain and delta soils in the Mississippi Alluvial Plain
(Fenneman, 1938) physiographic province (Schumacher and others, 1988?76 pedons,
Louisiana statewide).

The data sources, methods, and formulas used to estimate SOC storage and
inventory for these soils are discussed in Buell and Markewich (in press). The
S3C database will be updated as significant ?blocks? of new data are received,
checked for accuracy, standardized, and merged. The database is downloadable
through the links on this page. Three data files (pedon01, horiz01, and
taxon01) are provided in Microsoft Access 2000 and tab-delimited ASCII formats
(compressed in ZIP or TGZ volumes below). The database dictionaries are
provided in Microsoft Excel 2000 (pedvar.xls, hznvar.xls, and taxvar.xls) and
HTML (pedvar.htm, hznvar.htm, and taxvar.htm) formats. The database
dictionaries are also included in the field definition column of each Access
data table (pedon01, horiz01, and taxon01). The footnote references for the
field definitions are included in the Access version of the database as
separate tables (pedon01-footnotes, horiz01-footnotes, and taxon01-footnotes).

The pedon file (pedon01) contains site-level data such as soil series name and
geographic location as well as SOC storage and related ancillary data for
standard depth intervals; the horizon file (horiz01) contains the physical and
chemical characterization data for individual soil horizons; and the
soil-taxonomy file (taxon01) contains the descriptive data for all of the soil
series presently described by the U.S. Department of Agriculture, Natural
Resources Conservation Service, National Soil Survey Center, Lincoln, Nebraska.
The entire soil-series database was included in the taxonomy file to
facilitate updates to the pedon and horizon files. As the pedon and horizon
files are updated, data for previously unrepresented soil series will likely be
added. It is the authors? intent that these data will be helpful to those
involved in ecological studies, environmental assessments, and landuse planning
efforts that require the use of SOC data.

[Summary provided by the USGS.]