The database represents delineations of known aspen stands where aspen assessments were collected in the Klamath National Forest, Siskiyou County, California. The Ecological Unit Inventory is a data set compiled by the Klamath National Forest between 1991 and 1999. Aspen stands were interpreted using USGS 1m resolution grey scale aerial photography (DOQQs) captured during the summer of 1993. The polygon layer was digitized on a computer screen using the aerial photography to identify stand boundaries. The stands were evaluated based on criteria that included seral stage, tree size, primary and secondary dominant trees species, and vegetation category type. Associated with this polygon layer is a point layer (KLAMATH_NF_EUI_PTS) containing aspen stand assessments conducted in conjunction with the aspen stand delineations. Data Compilation: The Aspen Delineation Project (ADP) is a collaborative effort of the U.S. Forest Services Pacific Southwest Region, the California Department of Fish and Games Resource Assessment Program, and the California Office of Bureau of Land Management. Principal Investigator for ADP is David Burton; visit: www.aspensite.org for more information regarding the ADP. The Department of Fish and Games, Resource Assessment Program compiled this information from the collaborating agencies and other researchers, and formatted the data into a common database for the purpose of facilitating access to data related to the conservation of Quaking Aspen in California. This information portal falls within the ADP goals to help agencies and land managers identify, map, treat, and monitor aspen habitats. This dataset is a portion of a master database compiled during a year long effort in 2005 to pull together current GIS layers and maps depicting Aspen communities in California.