Colorado Division of Wildlife, Habitat Section Colorado Gap Analysis Land cover Maps

Colorado's land cover classification system was based on that developed for the Wyoming Gap Analysis Project. The land cover data layer was constrained by several practical considerations. First, the layer must have utility for modeling of vertebrate habitat. The typal resolution must be fine enough to relate to habitat descriptions utilized by the Colorado Division of Wildlife and other sources. Second, because of time and budget considerations, the map must be created using Landsat TM imagery as the primary data source. This means that land cover types must be distinguishable on the satellite imagery. Finally, because the map will be part of a larger regional Gap Analysis, it must be consistent with the classifications of surrounding states.

This classification system was designed to provide a realistic degree of typal resolution for the purposes of Gap Analysis for Colorado, given constraints of the data and practical mapping standards. The goal of the vegetation portion of the Gap Analysis is to map the extent and distribution of the existing land cover types of Colorado. Individual map units (polygons) representing land cover types will be distinguished on imagery based on Thematic Mapper data resampled to 100 m pixel resolution. Identification of the land cover types will be inferred from color, pattern and context of the imagery, together with ancillary data such as altitude, and other available map and field data.

The mapping standard for polygon size is mandated at 100 ha (40 ha for riparian areas and waterbodies) minimum mapping unit (MMU). This standard sets a practical limit to the degree of definition that can be attempted, even with higher resolution spatial data.

A hierarchical classification system was used for land cover types of Colorado. The first order subdivision of this classification system (seen to the left) is based on gross physiognomy of dominating plants where vegetation is intact, or on other dominating surface features such as bare rock or ice, where vegetation is not the dominating surface feature. This level is analogous to the "class" category of Jennings (1993).

The second order subdivision (List headers of the "spawned" list) corresponds with the widely used Anderson land use/land cover system (Anderson et al. 1976), and represents a mixture of finer physiognomic detail for vegetation, or designations of land uses. This set of headings is mainly useful as a means to find the correspondence between the Gap system and the Anderson system. Our usage of this terminology is given in parentheses following the Anderson term. This subdivision is analogous to the "subclass" category of Jennings (1993).

The third order subdivisions (clickable links) are the actual types that will be mapped. These subdivisions are based on the species dominants of vegetation dominated land cover, or analogous subdivisions for non vegetation dominated land covers. Seventy land cover types have been recognized from our experience in Wyoming and by integration of types listed by Bourgeron (1992), Baker (1984) and Alexander (1987). Each type is designated by a 5 digit code (left column) to be used in the attribute table with Arc/Info (the label for the map polygon). These 5 digit codes are expansions of numbers used in the Anderson land use/land cover system. The 5 digit codes used here retain compatibility with those used in the Wyoming Gap Analysis wherever possible. This is the "cover type" of Jennings (1993).

Fourth order subdivisions are not shown. These are based on more detailed floristic (or analogous) characteristics of polygons that will not be mapped as independent polygons but will, when possible be described in the Arc/Info attribute table. This subdivision mainly serves to indicate subtypes as examples of the third order subdivision for purposes of habitat correlation. Information at this level will require detailed ancillary information, usually ground reconnaissance, which will usually not be available. While this last subdivision is somewhat comparable to Jenning's (1993) "community type", we do not wish to imply that level of organization in this subdivision, given the time and resolution constraints listed above.

(For more information please download:   "Manual to Accompany the Gap Analysis Land Cover Map of Colorado" by Thompson et al. 1996)

**Please note: These maps use a status of 1 through 4 to denote the relative degree of management for biodiversity maintenance for a particular tract of land, where "1" represent the highest, most permanent and comprehensive level of maintenance, and "4" represents the lowest, or unknown status.  To view further explanation of the land stewardship codes, click here.