Pinaceae -- Pine family

    William W. Oliver and Russell A. Ryker

    Ponderosa pine (Pinus ponderosa), also called western yellow  pine, is one of the most widely distributed pines in western North  America. A major source of timber, ponderosa pine forests are also  important as wildlife habitat, for recreational use, and for esthetic  values. Within its extensive range, two varieties of the species currently  are recognized: Pinus ponderosa var. ponderosa (Pacific  ponderosa pine) (typical) and var. scopulorum (Rocky Mountain  ponderosa pine) (10). Arizona pine (P. arizonica), sometimes  classified as a variety of ponderosa pine (12,36,51), is presently  recognized as a separate species (45).