THE ALPINE MEADOW CLIMAX. 229 



in Eurasia. This unique extension of arctalpine plants has a definite historical 

 as well as physical basis. 



The total number of subdominants which form important societies is prob- 

 ably greater than for any other formation. The grassland climax approaches 

 it in this respect, while the prairie and the alpine meadow have much in com- 

 mon in so far as the number and luxuriance of the societies are concerned. 

 These are often so dense and continuous that the grass-like character of the 

 climax is completely hidden. The subdominants are even more strikingly 

 dwarfed than the dominants, chiefly because of a relatively greater emphasis 

 on the flower. In many the inflorescence is reduced to a single flower of 

 unusual size, while the stem is often less than an inch in height. A consider- 

 able number have assumed the mat or rosette habit and are essentially stem- 

 less, though this is more frequently the case in serai habitats. 



The true character of the alpine climax is often difficult of recognition, 

 owing to the wide variation in conditions over what appears to be fairly uni- 

 form terrain. Rock fields of all degrees, gravel-slides, bogs, wet meadows, 

 and temporary snow-seeps in all stages of succession frequently blur the out- 

 lines of the climax or break it up into many fragments. The real nature of 

 the climax is best seen in the Rocky Mountains of Colorado, where the alpine 

 areas are unusually extensive as well as free from snow during the summer. 

 In such places the general resemblance to a short-grass plain is striking. While 

 the alpine climax is ecologically a grassland, the predominance of sedges makes 

 it more accurate to refer to it as sedgeland. The term alpine meadow is 

 perhaps even more descriptive and is to be preferred to alpine heath, since 

 the latter is usually subclimax in character (plate 55). 



Extent. — In the view advanced here, the alpine and arctic sedgelands of 

 North America are regarded as constituting one formation. This seems to 

 accord with the general opinion that the arctalpine region is a unit life-zone 

 (Merriam, 1898). As such, the arctalpine climax extends across Arctic 

 America from Greenland to Alaska. The southern limit of it as a continen- 

 tal zone runs from central Labrador northwest to the lower Mackenzie River, 

 and then westward through Alaska. As is well known, the arctalpine climax 

 extends south over the isolated alpine summits of New England, but sweeps 

 much farther southward in the Rocky Mountains and the Sierra Nevada. 

 An alpine zone is found on the volcanoes of Mexico, but its relationship to the 

 present climax is uncertain. Along the Rocky Mountain axis the last out- 

 posts of the climax are found in the Sangre de Cristo Mountains of northern 

 New Mexico and the San Francisco peaks of northern Arizona. In California, 

 the single locality south of the Sierra Nevada is in the San Jacinto Range 

 (Hall, 1902: 16), where it is reduced to a mere fragment. By far the most 

 extensive development of the formation is found in the central Rockies of 

 Colorado and Wyoming and adjacent Utah, while the most complete and 

 continuous is in Colorado. 



Unity. — The ecologic and climatic unity of the arctalpine climax is so strik- 

 ing as to need little comment. The topographic and geographic unity appears 

 to be slight, but an adequate explanation is found in the correlating influence 

 of latitude and altitude. The general ecological unity appears to be fully 

 confirmed by the distribution and occurrence of the dominants as shown by 

 the table on the following page. 



