ISLSCP Initiative II

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Hydrology, Soils, & Topography Data

ISLSCP II Global Gridded Soil Characteristics

The Global Soil Data Task was an international collaborative project with the objective of making accurate and appropriate data relating to soil properties accessible to the global change research community. The collaborators are holders of major international pedosphere data sets, such as the United States Department of Agriculture (USDA), the Food and Agriculture Organization (FAO) of the United Nations, and the International Soil Reference and Information Centre (ISRIC), as well as national soils institutes, individual soil scientists, and users of soil data. The task was coordinated by the now defunct Data and Information System framework activity of the International Geosphere-Biosphere Programme (IGBP-DIS).
      The Global Soil Data Task assembled a reliable and accessible data set on pedosphere properties on a global scale. The data are sufficiently detailed to support rigorous analysis, and accessible to and understandable by soil scientists and non-soil scientists alike. The immediate goal was to supply pedosphere information to global change researchers, but the unification and distribution of the existing soils data bases is of great benefit to all researchers, not only those directly involved in global change studies. The task was enabled by the active participation of the principal international custodians of pedosphere data.
      A CD-ROM disk containing extensive global pedon data, and the so-called "SoilData" software to create global gridded layers of selected soil parameters from the FAO Digital Soil Map of the World (DSMW) was one outcome of this IGBP-DIS activity which is currently available from the ORNL DAAC at http://daac.ornl.gov/ [Internet Link]. The ISLSCP II staff has used the IGBP-DIS data and software to generate two-dimensional gridded maps of 18 selected soil parameters, including soil texture, at a 1 by 1 degree spatial resolution and for two soil depths. All data layers have been adjusted to match the ISLSCP II land/water mask.

Data Provider: Robert J. Scholes, Eric Brown de Colstoun

Data Files (ISLSCP II Disc #1)

Data Set Documentation

Image Viewing Tutorial

File Information

The files have been compressed using the PKZip program. Each uncompressed file contains space-delimited ASCII text. The 1-degree data has 360 values per line and 180 lines of data (1 degree resolution). Each line is terminated by a newline character. The data are structured so that the upperleft corner of the first pixel is located at 90 North latitude and 180 West longitude. All values in these files are written as real numbers. Cells over water or permanent ice are assigned the value -99 or -77, respectively, on all data layers except soil texture, where they are assigned the values 0 and 13.

Parameter Name	Units	Description
bulk_dens	g/cm3	Bulk Density.
clay_perc	% w/w	% Clay Content.
field_cap	mm	Field Capacity (FC), with FC water potential = -10 kPa
ksat	cm/day	Saturated Hydraulic Conductivity or Ksat
nitrogen_dens	g/m2	Soil Nitrogen Density
org_carb_dens	kg/m2	Soil Carbon Density
org_carb_perc	%	Percent Soil Organic Carbon Content
pawc	mm	Profile Available Water Content (PAWC), with:       FC water potential = -10 kPa       WP water potential = -1500 kPa
res_wat_cont	cm3/cm3	Residual Water Content
sand_perc	% w/w	% Sand Content
sat_wat_cont	cm3/cm3	Saturated Water Content or Porosity
silt_perc	% w/w	% Silt Content
texture	N/A	12 Soil Texture Classes after USDA soil texture classes.
therm_cap	J/m3/K	Thermal Capacity, with 0, 10, 50 and 100 % volumetric soil-water fraction (i.e. four data files for each soil depth).
wilting_point	mm	Wilting Point (WP), with WP water potential = -1500 kPa

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Revision Date: November 3, 2004