114 CUMAX FORMATIONS OF WESTERN NORTH AMERICA. 



account is based chiefly upon the special investigations of the last six years, 

 since these were undertaken for the express purpose of determining the 

 structure and development of the climaxes and their indicator values. These 

 have been supplemented by the earlier work from 1896 to 1912, and by the 

 results of the writer's associates and students. 



1. The Grassland Climax: Stipa-Bouteloua Formation. 



1. True Prairie: Stipa-Koeleria Association. 



2. Subclimax Prairie: Andropogon Associes. 



3. Mixed Prairie: Stipa-Bouteloua Association. 



4. Short-grass Plains: Bulbilis-Bouteloua Association. 



5. Desert Plains: Aristida-Bouteloua Association. 



6. Bunch-grass Prairie: Agropyrum-Stipa Association. 



2. The Sagebnish Climax: Atriplex- Artemisia Formation. 



1. Basin Sagebrush: Atriplex- Artemisia Association. 



2. Coastal Sagebrush: Salvia- Artemisia Association. 



3. The Desert Scrub Climax: Larrea-Prosopis Formation. 



1. Eastern Desert Scrub: Larrea-Flourensia Association. 



2. Western Desert Scrub: Larrea-Franseria Association. 



4. The Chaparral Climax: Quercus-Ceanothus Formation. 



1. Petran Chaparral: Cercocarpus-Quercus Association. 



2. Subclimax Chaparral: Rhus-Quercus Associes. 



3. Coastal Chaparral: Adenostoma-Ceanothus Association . 



5. The Woodland Climax: Pinus-Juniperus Formation. 



1. Pifion-cedar Woodland: Pinus-Juniperus Association. 



2. Oak-cedar Woodland : Quercus-Juniperus Association. 



3. Pine-oak Woodland: Pinus-Quercus Association. 



6. The Montane Forest Climax : Pinus-Pseudotsuga Formation. 



1. Petran Montane Forest: Pinus-Pseudotsuga Association. 



2. Sierran Montane Forest: Pinus Association. 



7. The Coast Forest Climax: Thuja-Tsuga Formation. 



1. Cedar-hemlock Forest: Thuja-Tsuga Association. 



2. Larch-pine Forest: Larix-Pinus Association. 



8. The Subalpine Forest Climax: Picea- Abies Formation. 



1. Petran Subalpine Forest: Pioea- Abies Association. 



2. Sierran Subalpine Forest: Pinus-Tsuga Association. 



9. The Alpine Meadow Climax: Carex-Poa Formation. 



1. Petran Alpine Meadow: Carex-Poa Association. 



2. Sierran Alpine Meadow: Carex-Agrostis Association. 



THE GRASSLAND CLIMAX. 

 STIPA-BOUTELOUA FORMATION. 



General relations. ^The grassland is much the most extensive of all the 

 western formations. It ranges from central Saskatchewan and Alberta in the 

 north to the highlands of central Mexico on the south, and in its subclimax 

 form at least from Illinois on the east to California on the west. From its 

 great extent geographically and climatically, a question naturally arises as to 

 its unity. It may at once be said that any division of the vegetation of the 

 North American continent into major units would include this as one of the 

 most outstanding. The real question is not so much as io its unity as to 

 whether it should be called a formation or not. The study of vegetation is 

 still in such a stage that each ecologist will answer as his experience and 

 insight make possible. In attempting to arrive at a basic and subjective 

 concept founded upon development as the only real guide to relationship, it 

 seemed best to employ the term formation for the major unit of vegetation, 



