Successional Classification of Plants on a Desert Grassland Site in Arizona

Abstract

Vegetative cover, composition, and frequency studies on protected and grazed desert grassland ranges in Arizona provided quantitative data on the reaction of plants to protection and grazing. These data were used to classify plants as decreasers, increasers, and invaders on a deep upland desert grassland site. In the absence of fire or mesquite control, velvet mesquite, Arizona cottontop, sideoats grama, cane beardgrass, and poverty threeawns reacted as decreasers; Wright buckwheat, red threeawn, and Rothrock grama acted as increasers; and burroweed, sticky snakeweed, and Lehmann lovegrass were classified as invaders. Annuals were not measured, and perennial forbs were too limited in abundance to classify. Under climax conditions with recurring fires, all native species apparently reacted as above except mesquite, which reacted as an increaser on bottomlands and an invader of uplands.