18 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



Grassland. — The areas in which grasses form a nearly continuous 

 cover lie between 5,000 and 7,000 feet and usually close to the margin 

 of xeric or mesic forest. In fact, some of the best areas of grass lie 

 within the borders of the forest, and, therefore, can scarcely be regarded 

 as true grassland. Along the northern edge of the mesic forest which 

 covers the Mogollon Mesa is found a belt of grassland that lies partly 

 in the open and partly inside the margin of the forest. Unde«r virgin 

 conditions there were large areas in Apache, Navajo, and Coconino 

 Counties that then merited the designation of grassland but now must 

 be regarded as desert-grassland transition. Smaller areas also occurred 

 in Chino Valley, Yavapai County, in Sulphur Springs Valley, Cochise 

 County, and in other elevated valleys in Cochise and Santa Cruz 

 Counties. 



In Navajo and Coconino Counties the characteristic grasses are: 

 Festuca arizonica, Sporobolus interruptus, Muhlenbergia montana, 

 Agropyron smithii, Bromus ciliatus, Bouteloua simplex, Muhlenbergia 

 richardsonis. 



In the Chino Valley, Yavapai County, the commonest grasses are: 

 Muhlenbergia torreyi, Bouteloua gracilis, Stipa comata, Bouteloua hirsuta, 

 B. eriopoda f Aristida ternipes. 



In the southeastern counties the grasses that are most important 

 are: Bouteloua curtipendula, B. gracilis, B. rothrockii, Sporobolus 

 cryptandrus, Bouteloua eriopoda, B. hirsuta, Leptochloa dubia, Sporo- 

 bolus wrightii. 



Both in the north and the southeast the grasses are accompanied 

 by scattered individuals of a large number of species of herbaceous 

 root perennials, as well as by more infrequent small shrubs. 



Arizona Chaparral. — This type of vegetation is found throughout 

 the semiarid foothills of the Mogollon Mesa from the eastern border 

 of the State to the vicinity of Ash Fork and Skull Valley, and locally 

 farther west. In its typical form it usually occurs in belts or relatively 

 small areas between elevations of 4,000 and 6,000 feet. In the general 

 vicinity of Prescott it occupies slopes of all exposures between 5,000 

 and 6,000 feet, but at any given elevation there are differences in its 

 composition on slopes of different aspect. Open chaparral occurs on 

 north slopes as low as 3,500 feet in the vicinity of Roosevelt Lake and 

 small stands of it on south slopes are found exceptionally as high as 

 7,000 feet northeast of Pine, Gila County. Chaparral occurs on slopes 

 with stony or shallow soil just below the xeric forest. Its lower edge 

 is in contact with grassland northwest of Prescott and with succulent 

 desert southeast of Payson. None of the characteristic plants of the 

 chaparral are found in the succulent desert, but many of them occur 

 in the xeric or mesic forests, locally in close stands but more commonly 

 as scattered individuals. 



The dominant plant in the Arizona chaparral is Quercus turbinella 

 (scrub oak), which forms 80 percent of the stand in many localities. 

 Common associates are Arctostaphylos pungens (manzanita) , Rhus 

 trilobata (squawbush), Cercocarpus breviflorussmd C. betuloides (moun- 

 tain-mahogany), Ceanothus greggii (buckbrush), Garrya wrightii (silk 

 tassel), and Fallugia paradoxa (Apache-plume). These shrubs have a 

 relatively uniform height of 3 to 6 feet, occasionally broken by taller 

 shrubs or by yuccas. The leaves of the dominant plants are small and 

 thick and are evergreen in all but Rhus trilobata. The physiognomy of 

 the Arizona chaparral, and the sclerophyllous character of the leaves 



