18 BULLETIN 1423, U. S. DEPARTMENT OF AGRICULTURE 
rains certain areas near the coast are subject to periodic crustings 
of snow, and in such places herds may suffer great losses through 
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 affect 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 affects 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 important factor in 
reindeer grazing, especialty 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 the Equator to the poles; 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 Alaska are determined by a 
preference for the arctic and subarctic habitat; and within the 
habitat the varied local climatic conditions show a marked effect 
on the character and development of the growth. 
Moisture 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. 
LOCAL VARIATIONS 
There is often considerable variation in climatic conditions between 
localities, chiefly on account of topography. One locality may be 
particularly subject to frequent and severe storms, whereas much 
more moderate conditions simultaneously exist in immediately ad- 
joining areas. Again, in the general coast region there may be great 
variation in winter temperature as between the immediate 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 growth in spring. For example, in 1922, the growing season 
at Unalakleet opened four or five days earlier than at St. Michael, 
only 40 miles south; two weeks earlier than at Pastolik, 100 miles 
south; and two to three weeks earlier than at Nome, 150 miles north. 
