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 1s 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 
smithiz) 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 
