4 BULLETIN 1227, U. S. DEPARTMENT OF AGRICULTURE 



poda). The short-grass type is of greatest importance from the 

 forage standpoint when the blue grama is present in quantity, and 

 of least importance when it is associated with much ring grass. 

 The woolly-foot grama is a characteristic desert grass and is there- 

 fore of increasing importance toward the west and south, disappear- 

 ing altogether at higher elevations and toward the east. 



The tall grasses have nearly all disappeared from vast areas in 

 northern Arizona as a result of heavy overgrazing, the sand drop- 

 seed {Sporobolus cryptandrus) being the only one which is still 

 widespread and which will come back readily if conditions permit. 

 In certain favorable areas the western wheat grass {Agropyron 

 smithii) is still predominant, and such areas are of great importance, 

 because of the excellent quality and large quantity of the forage 

 produced. This wheat-grass type is especially important also because 

 wheat grass withstands grazing and trampling by cattle very well in 

 the situations where it has survived, and because the type contains 

 sand dropseed, which recovers quickly if given opportunity. 



The two types of grassland mentioned (the tall grass, characterized 

 by the western wheat grass ; and the short grass, characterized by blue 

 grama) are the most important of those found grazed by prairie dogs 

 in this region. The other types occur in washes which flood to such 

 an extent that prairie dogs can not colonize them, on rocky hills 

 where these rodents can not dig burrows, or in parks in the upper 

 plant formations where the animals can not live. The short-grass 

 and tall-grass forage types belong essentially to the same formation 

 and were originally much more closely associated. The coming 

 in of man with his herds of grazing animals has caused them to 

 segregate and form distinct consociations, or forage types (Clements, 

 1920; Loftfield, 1924). 



The experimental areas were established during the early spring 

 of 1918 by the writers, assisted by D. A. Gilchrist. After an ex- 

 tensive survey, the Coconino area was selected as a typical represen- 

 tation of the tall-grass type, and the Seligman area of that form of 

 the short grass most commonly found in northern Arizona. Another 

 tract was considered in the type where blue grama is associated with 

 ring grass, since this was more nearly representative of the short 

 grass as it occurs generally in the Western States. An additional 

 installation was made possible in a tract located in the short-grass 

 type and established under Mr. Gilchrist's direction on the Tusayan 

 National Forest, near Williams. 



Summarizing, the Coconino areas are representative of conditions 

 in the tall grass ; Williams, those in the short grass ; and Seligman, 

 of the zone of transition between the Great Plains and Desert asso- 

 ciations of the grassland climax. Results to 1922 from the Coconino 

 and Williams areas are presented, data from the Seligman areas 

 being omitted because experimental difficulties have so far prevented 

 the securing of significant data on rodent damage. 



THE COCONINO EXPERIMENT. 



THE AREA. 



The Coconino experimental tract is situated near Coconino, Ariz., 

 in the northern division of the Tusayan National Forest, 1 mile east 

 of the Williams-Grand Canyon road, and about 8 miles by road from 



