Mapping Methods

Mapping Conventions

The following summarizes the mapping approach used to provide an ecological context for the Catalina-Rincon Firescape project.  The mapping represents the landscape and finer land unit scales of the National Hierarchical Framework of Ecological Units.  This product is the first approximation map for the Catalina Mountains and adjacent areas.   It is an update and refinement of the prototype landtype associations and provisional ecological landtypes developed for the Rincon Mountains and environs included in the yet to be published Landtype Associations of Southeastern Arizona (Cleland, el al. 2008). 

Landtype Associations

Landtype Associations (LTAs) represent the landscape scale of the National Hierarchy of Ecological Units (Cleland and others, 1997).   The dominant mapping criteria include landforms, geologic materials, and potential vegetation patterns.   LTAs capture repeatable patterns of soil complexes and plant communities. An LTA is often relatively homogenous in its vegetation, but it may have contrasting plant communities associated with different landscape positions - say, north versus south slopes. The LTA polygons were drawn by Larry Laing, a soil scientist familiar with ecological mapping and aerial imagery interpretation. 

The first step is to collect the relevant 'layers' of data -- soils, geology, topography, elevation, climate, existing vegetation (e.g., ReGAP), and remote sensing imagery.  The analysis of the data begins with determining which landforms are distinctive at the landscape level. For instance, assorted mountain landforms with bedrock at or near the surface are distinguished from the deep valley fill deposits.  Alluvial fans and terraces adjacent to the mountains are separated from the valley floor.  Above the San Pedro River deposits from ancient lakebeds have eroded into something akin to badlands and are mapped separately. To see these differences in landform, Laing used a shaded relief map that is digitally manipulated to adjust the scale as well as the angle and position of the sun.

After the initial mapping of landforms, aided by satellite and aerial imagery, attention turned to a draft spatial geology map provided by the Arizona Geological Survey (Reynolds, 2007) and soil surveys (where available).  The landform patterns detected in the initial step usually coincide strongly with geologic materials and soil characteristics.  Next is to define the various life zones through the use of satellite and aerial imagery, topography (aspect, slope and elevation), existing vegetation maps, and local knowledge.   The final step is to validate the units on the ground and to make appropriate corrections based on field observations. This reality check consists of field reconnaissance of representative LTA components (referred to as ecological landtypes), noting their plant communities and physical attributes, as well as confirming boundaries. 

Ecological Landtypes

Ecological landtypes are subdivisions of landtype associations and represent the land unit scale of the National Hierarchy of Ecological Units (Cleland and others, 1997). They were mapped based on more localized or finer scale topographic, geologic, soil, and plant species association properties.  These units have land surface variations, and other physical and biological properties, that influence hydrologic function, moisture distribution and retention (which affect finer scale plant community composition and distribution), and basic land capability. ELTs range from having no or very few weakly developed drainage features to being densely dissected by deeply incised washes and streams; drainage patterns can also vary dramatically across these land areas.  Drainage (washes, streams, etc) characteristics (rocky, silty or sandy; confined or not; etc) are strongly dictated by the ELTs within which they originate or flow through.  Larger valley bottom or riparian units are mapped as separate ELTs and have features cumulatively derived from their respective watersheds.  While ELTs tend to be more homogeneous than LTAs due to their finer scale, they can have several components associated with different landscape positions, soils or other variability in complex areas.

Ecological Landscape Units

As used in this project, "ecological landscape units" are groupings of landtype associations with broadly defined similarities in vegetation, topography, geologic and soil features. They provide a "big picture" view of the ecosystems of the FireScape project area.  They are intended to provide a broader framework for the assessment of existing conditions and departures, desired conditions, and environmental implications.


Cleland, D.T.; Avers, P.E.; Jensen, M.E.; Bailey, R.G.; King, T.; Russell, W.E. 1997.  National Hierarchical Framework of Ecological Units.  Published in, Boyce, M.S.; Haney, A., ed. 1997.  Ecosystem Management Applications for Sustainable Forest and Wildlife Resources. Yale University Press, New Haven, CT. pp. 181-200 

Cleland, D.T.; Laing, L; Watson R.L.; Malusa, J.; Jordan, J.K.; Diamond D.D.; Robertson, G. 2008 (unpublished).  Landtype Associations of Southeastern Arizona.  Prepared with support of the Southern Arizona Office of the National Park Service, the Southwestern Region of the US Forest Service, the US Geological Survey, and the US Forest Service Southern Research Station.  361 p.

Cochran, C.C. and Richardson, M.L. 2003.  Soil Survey of Pima County, Arizona, Eastern Part. United States Department of Agriculture, Natural Resources Conservation Service in cooperation with the Arizona Agricultural Experiment Station

Digital orthophoto quadrangle (DOQ) courtesy of the U.S. Geological Survey

Digital elevation model data courtesy of the U.S. Geological Survey

Draft geologic map GIS shapefile of the Catalina and Rincon Mountains area (2007); provided through personnel communication with Richard, S.M.

National Agricultural Imagery Program (NAIP) imagery 2004; USDA, Farm Service Agency
Prior-Magee, J.S., K.G. Boykin, D.F. Bradford, W.G. Kepner, J.H. Lowry, D.L. Schrupp, K.A. Thomas, and B.C. Thompson, Editors. 2007. Southwest Regional Gap Analysis Project Final Report. U.S. Geological Survey, Gap Analysis Program, Moscow, ID.

Svetlik Jr., W. 2007.  Soil Survey of Cochise County, Arizona, Northwestern Part. United States Department of Agriculture, Natural Resources Conservation Service in cooperation with Redington Natural Resource Conservation District, Willcox-San Simon Natural Resource Conservation District, and the Arizona Agricultural Experiment Station
Landsat satellite imagery courtesy of the U.S. Geological Survey