THE PETRAN ALPINE MEADOW. 



233 



FiQ. 12. Monthly and 

 total rainfall for the al- 

 pine meadow climax, 

 summit of Pike's Peak, 

 14,100 feet. 



Factor and serai relations. From 1900 to 1906 quantitative studies were 

 made of alpine habitats and communities on Pike's Peak and the neighboring 

 Mount Garfield or King's Cone. These confirmed the general opinion as to tem- 

 perature and water relations, but not as to the light intensity. The annual pre- 

 cipitation on the summit of Pike's Peak (14,100 feet) is 30 inches; at Lake 

 Moraine (10,200 feet), which lies at the base of the Peak proper and in the sub- 

 alpine forest, it is 25 inches; at the Alpine Laboratory (8,500 feet) in the mon- 

 tane forest it is 22 inches; and on the short-grass plains at the base (6,000 feet) 

 it is 15 inches. The relative humidity on Mount 

 Garfield (12,500 feet) averaged 5 per cent higher than 

 at the Alpine Laboratory, but in spite of this the tran- 

 spiration was 25 per cent higher at the former. The 

 mean temperature is 19** on Pike's Peak, 36** at Lake 

 Moraine, and 47 at Colorado Springs on the plains. 

 During the growing season, temperatures averaged 15 

 higher at the Alpine Laboratory and 25 higher at 

 Manitou (6,500 feet) than on Mount Garfield. 

 Comparative light readings have been made for several 

 summers at Pike's Peak and Mount Garfield and at 

 the Alpine Laboratory, Manitou, and Colorado 

 Springs. For the most part, these have given identi- 

 cal results at the different altitudes in spite of a range 

 of 8,000 feet. This is probably to be explained by the low humidity (fig. 12). 



The typically climax condition of the association is marked by the sod- 

 forming or densely cespitose sedges, such as Carex rupestris, filifolia, pyrenaica, 

 nigricans, nardina, engelmanni, etc. These are also of low stature, usually 

 2 to 5 inches, and rarely as much as 6 to 8 inches. Juncodes spicatum and 

 Elyna hellardi are nearly equivalent to the low sod-forming sedges, but they 

 have a wider range of adjustment. In the direction of the xerosere subclimax 

 lie most of the grasses, some of which, such as Festuca brachyphylla and Poa 

 Uttermanni, are often if not usually serai in character. Most of them are 

 bunch-grasses and are 6 to 12 inches tall. The taller sedges, such as Carex 

 f estiva and C atrata, which range from 1 to 2 feet high, are more or less similar 

 in nature. Toward the hydrosere occur such species as Carex iolmiei, nova, 

 apd bella, which are tall and more or less sod-forming, and the rushes. These 

 lead to species of Carex and Juncus that are distinctly hydrophytic and serai. 



SOCIETIES. 



The number of societies is very large, and no endeavor has been made to 

 include them all. The following Ust is based primarily upon studies in Colo- 

 rado, but it is representative of the entire central portion and even of such 

 outlying areas as the San Francisco peaks. The endemic species drop out 

 for the most part in Montana and Alberta, and there is an increasing number 

 of species from the Arctic and Pacific associations. Of the 80 societies given, 

 29 are endemic, 32 occur in the Pacific alpine meadows, 32 in Arctic America, 

 and the same number in Eurasia. The identity in number in the last three 

 is merely a coincidence, for the species are not the same throughout. 



The great majority of the societies listed belong typically to the climax, 

 but some are normally serai or subclimax dominants which persist into the 



