PLANTS IN ARCTIC-ALPINE ENVIRONMENT — SHETLER 477 



and tundra. Here there is a certain tension between forest and tundra, 

 where the trees can't decide, as it were, when to give up. This vacilla- 

 tion is depicted well for two Alpine areas in some of the pictures of 

 plates 1 and 8. 



THE ENVIRONMENT 



Frigid temperatures, low precipitation, high winds, permanent frost, 

 and a very asymmetric annual light regime are a few of the problems 

 that confront plants of the Tundra. Add to this the contingent factor 

 of an extremely short growing season, and you have quite an order 

 for any plant species to tolerate. 



If there is any one fact that virtually everyone thinks he knows 

 about arctic-alpine regions, it is that the climate is cold — very cold. 

 The average person pictures the Arctic as a place of perennial snow 

 and subzero weather, barren and virtually lifeless — in short, nothing 

 but an icebox. One cannot deny that the Arctic can be very cold 

 and very barren, but this "icebox" image grossly distorts the true pic- 

 ture and hides the real significance of temperature as a variable in the 

 arctic-alpine environment. Throughout vast parts of the Arctic there 

 comes a perfectly orthodox shirtsleeve summer, which though abbrevi- 

 ated peiTtiits a remarkably diverse and luxuriant growth of plants. 



Temperature is critical in the arctic-alpine environment both for its 

 low extremes and low means, although perhaps more so for the latter 

 than the former. We can gain some insight into this variable by exam- 

 ining a specific case. The data on climate which follow have all been 

 drawn from the U.S. Department of Agriculture's Yearbook of Agri- 

 culture for 1941, Climate and Man. Despite the date of publication, 

 there is no reason to believe that the overall picture has changed over 

 the past 23 years. 



Let us examine in some detail the conditions at Point Barrow, 

 Alaska, which lies north of 71° N. latitude, well within the Arctic by 

 any definition, and about as far north as one can get on the North 

 American Continent. Over a 25-year period the average temperature 

 for the warmest month, July, was 40° F., only 8° above freezing, and 

 for the coldest month, January, — 17° F. The recorded minimum over 

 this period was a frigid —56° F. and the maximum a balmy 78° F. 

 Thus the average range here is from —17° to 40° F., or 57°, which is 

 more or less typical for the Arctic coast of Alaska in general and for 

 many other areas throughout the Arctic. This range is of course less 

 than half as great as the 134° range between the 25-year extremes. 

 Quite clearly arctic plants have got to exist on a relatively low annual 

 heat budget, when the temperatures of the wannest month do not aver- 

 age more than 40° F. In fact, at Barrow they drop below zero an 

 average of 170 days a year, almost half the year, and some snow falls 



