22 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



are not far above the level of the sea. But if we apply the term 

 "Arctic" here, it must denote the "Low Arctic." 



The Aleutian district is unique. For animal life, it combines 

 favorable climatic factors and unusual food resources. It is a 

 focal point to which animal life has been coming from north 

 and south, and east and west, and it is a melting pot for faunal 

 elements from two continents that have not yet reached equilib- 

 rium. It is necessary to keep in mind the fluid nature of the 

 Aleutian biota in arriving at any system of zonal delineation. 



From a purely descriptive standpoint, the fauna of the Aleu- 

 tian district stands apart, and it may well merit distinction as 

 the "Aleutian Fauna." There may be good reason to consider it 

 as a unit of a more comprehensive Bering Sea fauna. 



VEGETATION 



In 1937, Eric Hulten published (in Stockholm, Sweden) "Flora 

 of the Aleutian Islands and Westernmost Alaska Peninsula with 

 notes on the flora of Commander Islands." The same author has 

 also published "Flora of Alaska and Yukon," in 10 parts, issued 

 from 1941 to 1950. This work covers the botany of the Aleutian 

 district so thoroughly that no detailed account of the vegetation 

 need be attempted here, except for mention of some prominent 

 plant associations and their distribution. 



The first consideration is the distribution of forests. The 

 spruce-forest edge is found midway on Kodiak Island and in 

 the general vicinity of Becharof Lake on Alaska Peninsula. We 

 find elements of the flora, as well as some of the birds, converg- 

 ing on the base of Alaska Peninsula from two directions. From 

 the east, the Sitka spruce (Picea sitchensis) of southern Alaska 

 has made its way to Kodiak Island at the base of Alaska Penin- 

 sula, out to the region about Becharof Lake, and now it consti- 

 tutes the principal forest growth in this area. The status of the 

 white spruce (Picea glauca) is less certain, but this interior- 

 Alaska tree has come down from the north to at least as far as 

 Bristol Bay, near Nushagak, and it may be considered to have 

 barely reached the border of Alaska Peninsula, inland from the 

 coast. The birch (Betula kenaica) is associated with the conif- 

 erous growth in all this forested area. 



With the exception of this meager forest, in all lowland por- 

 tions of Alaska Peninsula and Unimak Island, and to some extent 

 as far west as Unalaska, tall vegetation is in the form of shrub 

 thickets — dwarf birch (Betula nana exilis), willow, and alder. 

 Alder (Alnus crispa sinuata) is particularly prevalent and forms 



