Description: Ecological Response Units (ERUs) facilitate landscape analyses and planning. The framework represents all major ecosystem types of the southwest region, and represents a stratification of biophysical themes. ERUs are used to define historic/reference conditions within a mapping unit by integrating site potential (soil physical and chemical properties, geology, geomorphology, aspect, slope, climate variables, and geographic location), fire regime (historic and contemporary), neighboring vegetation communities, and seral state sequence.The process by which this dataset was created is as follows:The input data were forest Terrestrial Ecological Unit Inventory (TEUI) survey data that were crosswalked to the ERU list, ERU version 4, corrections to ERU version 4 utilizing a climate gradient to identify anomalous attribution, a collaborative review product with the University of Arizona’s Ecologist Jim Malusa, Integrated Landscape Assessment Project (ILAP) data, Regional Riparian Mapping Project (RMAP) data, and subclass information derived from an ILAP grid analysis. The data layers listed above were assembled in a hierarchical order starting with the ERU version 4 data through a series of geoprocessing updates. Highest confidence was placed on TEUI data and RMAP data so those datasets were burned into the product last. During key review periods by resource specialists, there were metrics built to analyze percent of ERUs that lay on the border of a climate gradient or a Southwest Biotic Community (Brown and Lowe). These metrics were used to inform attribution for ERUs that needed evaluation by the resource specialist. Additional processing was performed using the Eliminate tool to reduce the amount of “noise” in the dataset brought on by fragmented polygons smaller than a parametric minimum map unit. The minimum map unit was defined as 1 hectare for grassland, shrubland, forest, woodland, and great plains system types and 1 acre for riparian types. By virtue of the Eliminate tool, polygons that did not meet the minimum map unit were merged to a neighboring polygon that shared the largest boundary. RMAP data was used as an exclusion dataset and no changes were made to that via the Eliminate processing. Multiple QA/QC reviews were performed at many stages of the building of the layer and as products were being finalized. During these reviews, updates were made to the layer as needed. The creation of the regional extent layer came via a marriage of two halves of the region. The southern product was delineated by ecoregion boundaries that formed the combined context area of analysis for the Gila and Lincoln National Forests. This was necessary due to time constraints imposed by Forest Plan Revision Assessments for those forests. The remainder of the region was assembled independently but in an identical way to the southern portion. Once complete, the two datasets were joined together via a data load to eliminate any possibility of errors brought on by additional geoprocessing. The regional product was then reviewed to identify any errors along the boundary between the two layers. The full dataset was added to the corporate SDE as a beta product and will be considered complete and in a maintenance as needed status. Additional changes to the dataset ought to be documented as process steps.This layer was developed through iterative and collaborative efforts of Forest Plan Revision assessment.