Terrestrial Ecosystems (
U.S. metadata) were mapped by delineating physically distinct areas as the fundamental structural units and subsequently labeling these into the NatureServe classification. Structural units were developed from the union of source layers including those listed below.
Topograhic Moisture Potential (
U.S. metadata,
Africa metadata) was derived to help contribute substrate moisture regimes and was based on the derivation of ground moisture potential using a combination of computed topographic characteristics and mapped National Wetland Inventory boundaries.
Land Surface Forms (
U.S. metadata,
Africa metadata) were generated based on the methodology developed by the Missouri Resource Assessment Partnership (MoRAP) that made modifications to Hammond's land surface form classification. An additional class called drainage channels was used to identify wet and dry river channels.
Surficial Materials Lithology (
U.S. metadata,
Africa metadata) was derived from the 28 lithology classes identified in the USGS map "Surficial Materials in the conterminous United States". These were generalized and reclassified into a set of 18 lithologies that typically control or influence the distribution of vegetation types.
Isobioclimates (
U.S. metadata,
Africa metadata) were generated by combining the thermotypes (warm/cold) and ombrotype (dry/wet gradients) climate classes produced from the Rivas-Martínez method based on the concept of a quantifiable classification system which would closely relate the distribution of vegetation to climatic parameters and indices.
More detailed information about these layers is on the appropriate Project Areas page, and the
U.S. Raster Lookup Tables and
Africa Raster Lookup Tables are also available for use.
Quick Extents:
U.S. Department of the Interior |
U.S. Geological Survey