The Ecological Systems Classification for the US, accessible via the NatureServe Explorer website, served as the basis for classification and mapping. This classification has been modified for Oklahoma and a 69-page document was delivered under separate cover to the Oklahoma Department of Wildlife Conservation. The basic classification and mapping methods incorporated remote sensing for land cover (about 15 classes), and overlay of digital soils, %slope, and streams to create the map. A total of 3,709 georeferenced, quantitative data points were gathered in a systematic way, and 1,114 more georeferenced points were gathered to help improve the map. A total of 165 vegetation types were mapped. Summary statistics from points show that three of the most frequent six species in the herbaceous layer were non-native species. Post oak was by far the most common tree encountered. The primary grassland types of Oklahoma together accounted for more than a third of the area of the state, and cropland made up more than 15% of the area. More than half of the mapped types occupy fewer than 10,000 hectares of the state.
