18 



BULLETIN 1423, U. S. DEPARTMENT OF AGRICULTURE 



rains certain areas near the coast are subject to periodic crustings 

 of snow, and in siicii places lierds may sutl'er <ireat losses throu<rh 

 starvation, since the animals can not paw through the hard crust to 

 get feed. In case of crusting, the herd must be promptly moved 

 back to protected areas in the interior hills. 



Under ordinary conditions the depth of snow on the winter range 

 along the coast does not seriously aftect grazing, since part of the 

 area at least is generally exposed to the winds and does not become 

 deeply covered. In the interior, however, particularly on timbered 

 flats and bench -land country, there is less drifting, and the depth 

 of snow then atfects the selection of winter range. Where consider- 

 able drifting takes place, certain areas may become so deeply covered 

 that the animals can not paw through the snow to reach the vegeta- 

 tion. Ordinarily, to reach the lichen forage reindeer will read- 

 ily paw through as much as 2 feet of packed snow and 3 feet or 

 more of loose snow. 



A FORAGE FACTOR 



The effect of climate on plant growth is an imi:)ortant factor in 

 reindeer grazing, especially as regards the lichen vegetation. Lichens 

 attain their maximum development and number in tropical regions. 

 The proportion of cryptogamic to phanerogamic vegetation increases, 

 however, from tlie E((nat()r to the }X)les; thus in Alaska the propor- 

 tion of lichens to other vegetation is relatively high. Furthermore, 

 the numerous species of lichens vary in their climatic requirements, 

 so that the predominating species in xVlaska are determined by a 

 preference for the arctic and subarctic habitat; and within the 

 habitat the varied local climatic conditions show a marked elTect 

 on the character and development of the growth. 



JNIoLsture is a most potent agent in the development of the lichen, 

 but an excess of moisture seems prejudicial to lichen development, 

 in that it produces a sterile state of the thallus and favors the produc- 

 tion of pulverulent and dwarfed forms. Season and vicissitudes of 

 climate may variously affect the lichen growth, in some species 

 causing changes in chemical composition and in others altering the 

 form of the thallus, since under abnormal conditions the gonidal 

 element of the thallus may become productive and give rise to 

 various malformations. 



■V 



LOCAL VARIATIONS 



There is often considerable variation in climatic conditions between 

 localities, chiefly on account of to[)ography. One locality may be 

 jDarticularly subject to frequent and severe storms, whereas nuich 

 more moderate conditions sinndtaneously exiwt in immediately ad- 

 joining areas. Again, in the general coast region there may be great 

 variation in winter temperature as between the iinuiediate coast and 

 the interior; over a distance of 40 miles the difference may be as 

 much as 20° F., the lower temperature occurring inland. Consider- 

 able difference between localities is also shown in the beginning of 

 plant giowth in spring. For example, in 1922, the growing season 

 at Unalakdeet opened four or five days earlier than at St. Michael, 

 only 40 mile.s south; two weeks eaiiier than at Pastolik. 100 miles 

 south; and two to three weeks earlier than at Kome, 150 miles north. 



