Pinyon and Juniper Invasion in Black Sagebrush Communities in East-Central Nevada

As a means of studying inter- and intrazonal invasion in black sagebrush (Artemisia nova A. Nels) communities six maturity classes were established for pinyon (Pinus monophylla Torr. and Frem.) and juniper (Juniperus osteosperma (Torr.) Little) in east-central Nevada. Pinyon and juniper invade and increase in black sagebrush communities until the understory, except for a few hardy plants, is eliminated. Juniper invades first and tends to be eventually replaced by pinyon. Accelerated invasion by both species started about 1921 and is closely related to overgrazing, fire suppression, and climatic change.