276 GRAZING INDICATORS. 



that the need of a more distinctive term is clearly felt. In so far as grazing is 

 concerned, the term grazing type might well serve the purpose, though forma- 

 tions and associations, as well as serai communities, are also grazing types. 

 The grouping of consociations within the association is typical of all climaxes, 

 however, and seems to warrant a special term for those who need a complete 

 and detailed analysis of vegetation. After an extended consideration of the 

 possibilities, it has seemed desirable to definitize the term fades for serai 

 groupings and to make a new word, faciation, for climax groupings. These 

 are derived from the same root, fac, shine, and possess the same basic mean- 

 ing, namely, appearance, aspect, or form. The two terms conform to the 

 mutual relation seen in associes and association, consocies and consociation. 



Savannah as an indicator. — Throughout the present treatment, the word 

 savannah is used for the community which characterizes the ecotone between 

 two climax formations. In its most typical expression, it consists of grasses 

 and low trees or tall shrubs, and occurs in the hot, dry regions of the South- 

 west. Other communities are so similar that it is impossible to exclude them, 

 and hence open pine forest and woodland with a grass cover are also called 

 savannah. Closely related to these are the so-called natural parks of the 

 Rocky Mountains in which serai grassland is surrounded and more or less 

 invaded by trees. Such parks occur in both the montane and subalpine zones. 

 When the ecotone lies between forest or woodland and scrub, the general 

 ecological relations are similar to those of savannah, but the grassland is 

 replaced by sagebrush, chaparral, or desert scrub. The trees stand more or 

 less scattered in the scrub, and the indications of the community are primarily 

 those of the latter. The failure to recognize this similarity to savannah has 

 led to confusion with reference to the distinctness of the scrub climaxes in 

 rough regions where they are interspersed with trees. Savannah has been 

 so generally linked with the presence of grasses that it seems unwise perhaps 

 to broaden its meaning to include areas of scrub with taller trees, and conse- 

 quently the word park has been used for the latter. Thus, a sagebrush 

 savannah is one in which sagebrush is scattered through grassland, while 

 a sagebrush park is a community in which sagebrush is surrounded and 

 more or less invaded by trees or tall shrubs. 



In their typical form, both savannah and park are controlled by the grasses 

 or scrub, and the trees are more or less incidental. The transition to forest 

 or woodland is usually gradual, and it is impossible to draw a sharp line be- 

 tween the two. However, it is a simple matter to distinguish the general 

 areas from each other. As long as the trees or shrubs are far enough apart 

 so that their shadows do not touch, the grassland or scrub remains in control. 

 When they are sufficiently close to have their shadows overlapping during 

 most of the day, the grass or scrub dies out for lack of sun, or persists only in 

 small groups of much modified individuals. Tree and scrub savannah often 

 cover extensive areas to which they give the appearance of open woodland, 

 but the true nature of the community is indicated by the continuous carpet of 

 grass, which serves as the indicator. Sagebrush and chaparral parks are 

 usually more local, and they quickly pass into woodland on the one hand and 

 scrub on the other. They recur constantly, owing to the relatively small 

 difference in requirements between shrubs and small trees. Savannah proper 

 is probably due to the effect of climatic cycles and is thought to serve as an 





