Data Set Citation:
When using this data, please cite the data package:
NCEAS 2178: Jackson: Towards an explicit representation of root distributions in global models , National Center for Ecological Analysis and Synthesis , and Jackson R.
Global Distribution of Root Profiles in Terrestrial Ecosystems
nceas.199.1 (https://knb.ecoinformatics.org:443/knb/metacat/nceas.199.1/nceas)
General Information:
Title:Global Distribution of Root Profiles in Terrestrial Ecosystems
Identifier:nceas.199
Alternate Identifier:Root_profiles_D50D95.csv; root_profiles_references.txt (also in .pdf and .rtf formats)
Abstract:
A database of vertical root profiles for global terrestrial ecosystems was assembled from the primary literature in order to characterize the belowground structure of global vegetation types and to study relationships of belowground vegetation structure with climate, soil characteristics, and aboveground vegetation structure. Variables used to characterize belowground vegetation structure include the depth above which 50 percent of all roots are located and the depth above which 95 percent of all roots are located in the profile. For each root profile, information recorded includes latitude and longitude, elevation, soil texture, depth of organic horizons, type of roots measured (e.g., fine or total, live or dead), sampling methods, units of measurements (root mass, length, number, surface area), and sampling depth. Some profiles lack information on one or more of these variables. Also recorded are presence and dominance of plant life forms (including succulents, forbs, grasses, semi-shrubs, shrubs, and four categories of trees: needle-leaved vs. broadleaved, evergreen vs. deciduous) and whether the vegetation was relatively natural or altered by humans (e.g., forest plantations and pastures). The database also includes data on mean annual precipitation and the seasonal distribution of precipitation. Data sets that are related to this root profile data set include root nutrient concentrations (for approximately 372 site-pit-depths from 56 papers in Gordon and Jackson 2000) and root turnover rates (data for approximately 188 sites from 152 papers that were used to estimate root turnover rates for 341 site-vegetation combinations in Gill and Jackson 2000). The three recent papers include most of the data contained in the initial root data set; however, some observations may have been excluded because of more stringent selection criteria. Many of the source papers provided data for all three of the rooting data sets and users are encouraged to review all three data sets. The Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) for Biogeochemistry Dynamics organized and formatted these data for long-term archive. The archived data are contained in two files: (1) The ecosystem root profiles file, containing estimated 50 percent rooting depths (D50) and 95 percent rooting depths (D95) plus information on sampling methods, vegetation, climate, and soil, and (2) a file containing the references to file (1). These files were obtained from H. Jochen Schenk, Department of Biological Science, California State University Fullerton, California, in February 2003. The data were placed into a spreadsheet format and stored as an ASCII comma-separated (.csv) file. Missing values are represented by -999.
Keywords:none:
  • root profiles (theme)
none:
  • global (place)
none:
  • terrestrial ecosystems (place)

Involved Parties

Data Set Creators:
Organization:NCEAS 2178: Jackson: Towards an explicit representation of root distributions in global models
Organization:National Center for Ecological Analysis and Synthesis
Individual: Robert B. Jackson
Address:
Department of Botany University of Texas, Austin,
Austin, Texas 78713-7640 USA
Phone:
(512)471-5858 (voice)
Phone:
(512) 471-3878 (Fax)
Email Address:
rjackson@mail.utexas.edu
Data Set Contacts:
Individual: Robert B. Jackson
Address:
Department of Botany University of Texas, Austin,
Austin, Texas 78713-7640 USA
Phone:
(512)471-5858 (voice)
Phone:
(512) 471-3878 (Fax)
Email Address:
rjackson@mail.utexas.edu
Associated Parties:
Individual: H. J. Schenk
Metadata Providers:
Individual: Andrea Chadden

Data Set Characteristics

Geographic Region:
Geographic Description:Global.
Bounding Coordinates:
West:  -157  degrees
East:  176  degrees
North:  76  degrees
South:  -46  degrees
Time Period:
Begin:
1925-01-01
End:
2000-12-31

Sampling, Processing and Quality Control Methods

Step by Step Procedures
Step 1:  
Description:

Data Synthesis/Calculation

The 50 percent and 95 percent rooting depths were calculated by fitting a non-linear smoothing function (a logistic dose-response curve) to each cumulative root profile and interpolating the 50 percent and 95 percent rooting depths. For details see Schenk and Jackson (2002) or the companion file, A Database of Root Profiles for Global Vegetation [ ftp://daac.ornl.gov/data/global_vegetation/root_profiles/comp/root_profiles_methods.pdf ]. Fewer than 10 percent of all profiles in the database were sampled to the maximum rooting depth, which means that more than 90 percent of these interpolated rooting depths are underestimates of the true 50 percent and 95 percent rooting depths at the respective sites. To correct for this sampling error, incompletely sampled profiles (those not sampled to the maximum rooting depth or to at least 3 m depth) were extrapolated by means of the same mathematical function used to interpolate completely measured profiles. To avoid excessive errors, extrapolations were restricted to a maximum sampling depth of either twice the sample depth or to 3 m depth, whichever was smaller. Profiles for tundra and wetlands were not extrapolated beyond the measured depth. For extrapolated profiles, both the 50 percent and 95 percent rooting depths based on interpolating to the maximum sampling depth and the 50 percent and 95 percent rooting depths based on extrapolating the profiles are included in the data file. The Schenk and Jackson (2002) paper is available as a PDF file at http://www.biology.duke.edu/jackson/em02.pdf. This data set builds on the initial root data compiled by R. B. Jackson in the mid-1990s (see Jackson et al. 1996; Jackson et al. 1997). The data set of 115 vertical root profiles (Jackson et al. 1996) was expanded to include 475 profiles from 209 geographic locations for the analyses presented in Schenk and Jackson (2002). The current version of the data set (as of February 25, 2003) contains root profiles for approximately 298 sites with 565 profiles.

Data Set Usage Rights

no restrictions
Access Control:
Auth System:knb
Order:denyFirst
Metadata download: Ecological Metadata Language (EML) File