NATURAL AREAS AND REGIONS 



119 



their northern limit within it. Such 

 comprise the following: Rangifer cari- 

 bou, Alces, Sciuropterus, Sciurus, Castor, 

 Evotomys, Fiber, Erethizon, Lepus ameri- 

 canus, Lynx, Lutra, Lutreola, Mustela, 

 and others. Among birds, the pigeon 

 hawk, great gray owl, hawk owl, pine 

 grosbeak, Harris sparrow, tree sparrow 

 and gray-cheeked thrush breed princi- 

 pally within it. Its trees are not pecu- 

 liar, though the Banksian pine (Pinus 

 divaricata) and balsam poplar (Populus 

 balsamifera) barely enter its borders. 

 Its shrubs are mainly species that over- 

 lap from the adjoining zones. Among 

 those which seem to reach their greatest 

 perfection in the belt of stunted trees 

 may be mentioned Empetrum nigrum, 

 Ledum palustre, Vaccinium uliginosum, 

 Vitisidaea vitisidaea, Oxycoccus oxycoc- 

 cus, Arctous alpina, and Betula nana. 



On the southwest shores of Hudson 

 Bay this zone occupies a strip about 200 

 mi. in width. Thence its southern 

 boundary extends inland, passing 

 through Athabaska Lake, and then 

 bending northward crosses Great Slave 

 Lake just east of the mouth of Slave 

 River. Practically all of the northern 

 shore of Great Slave Lake lies within 

 its limits. Beyond here its lower boun- 

 dary is very uncertain. It is bounded 

 by a strip of well wooded country, 

 probably only a few miles in width, 

 extending northward along the Macken- 

 zie. This southern influence ceases .to 

 be effective near the mouth of Bear 

 River, and the southern limit of the 

 zone may be considered to cross the 

 Mackenzie near latitude 65. Thence 

 it bends southward, following the west- 

 ern border of the Canadian strip. Here, 

 as on the eastern side, the position of 

 the boundary is unknown, but because 

 of the great altitude of most of the 

 country west of the Mackenzie and north 

 of the Liard the southern heavy timber 

 (Canadian Zone) can not extend far 

 from the river and the stunted timber 

 (Hudsonian) must cover nearly the 

 entire area, exclusive of the alpine sum- 

 mits of the mountains. A large area 

 to the south of the Liard, including most 



of the country drained by its southern 

 tributaries, and practically all the 

 country about its headwaters in north- 

 eastern British Columbia and south- 

 eastern Yukon below the timberline, 

 are also in this class. The latter area 

 will be considered more fully later. 



C. Barren grounds (Arctic Zone}. 

 North of the Trans-continental Forest 

 lies an immense area usually called the 

 Barren Grounds, from its treeless con- 

 dition, which results from a summer so 

 short that reproduction can not be 

 effected. This condition, however, does 

 not prevent the perpetuation of many 

 species of shrubby and herbaceous plants 

 and a rich insect fauna, which together 

 support a great variety of vertebrate 

 life. 



Shrubby plants are common, Rhodo- 

 dendron lapponicum, Cassiope tetragona, 

 Dryas integrifolia, and several dwarf 

 willows being perhaps the most charac- 

 teristic. Many other less strictly rep- 

 resentative plants also are abundant. 

 The area is further characterized by the 

 presence of certain mammals, as the 

 lemmings of the genera Lemmus and 

 Dicrostonyx, the Arctic fox (Alopex 

 lagopus innuitus), musk-ox (Ovibos mo- 

 schatus), Barren Ground caribou (Ran- 

 gifer arcticus), and Arctic hare (Lepus 

 arcticus canus). Most of the birds 

 which characterize this area are mi- 

 gratory, spending only the breeding 

 season within its boundaries. They 

 comprise, among the Anatidae, the 

 various species of the genus Chen, the 

 brent geese, and one or two genera of 

 maritime ducks; and among the Limi- 

 colae, the genera Lobipes, Phalaropus, 

 Macrorhamphus, Pisobia and related 

 genera, Crocethia, Tryngites, Numenius 

 (hudsonicus and borealis), Squatarola, 

 Pluvialis and Arenaria. The Gallinae 

 are represented by willow and rock 

 ptarmigans, the Raptores by the gyr- 

 falcons, and the Passeres by the Snow- 

 flakes, Lapland and painted longspurs 

 and the pipits. 



D. Local conditions. 1. The larger 

 rivers, the Athabaska, Peace, Slave, 

 Mackenzie, and Liard, have a moder- 



