Brown's Juniper-Pinyon Woodland is commonly called Pinyon-Juniper (PJ) woodland. Merriam included this biome in his Upper Sonoran Life Zone. The two major trees are juniper and pinyon although the species of each may change from site to site. Juniper is also more drought tolerant than pinyon and some sites may lack pinyon completely. Pinyon-Juniper woodland is best developed between 5000-6500 feet elevation, although it may occur outside this range, such as the hot, dry slopes of Mt Elden at 8000 feet. The Rocky Mountain Pinyon (Pinus edulis) is the common pinyon in much of northern Arizona although it is replaced by the Great Basin pinyon (Pinus monophylla) in northwestern Arizona. Northern Arizona is the meeting ground for two junipers. One-seeded juniper (Juniperus monosperma) is common east to Texas, while Utah juniper (Juniperus osteosperma) is more common north and west in the Intermountain Region. Two rare species often associated with chaparral below the Mogollon Rim are redberry juniper (Juniperus coahuilensis) and single needle pinyon (Pinus monophylla var. fallax).