254 



NATURALIST'S GUIDE TO THE AMERICAS 



II. PHYSIOGRAPHY 



The province may be divided into 

 four physiographic regions. 



1. The Rocky Mountain region: In 

 the south of the province the mountains 

 occupy a narrow zone some 25 mi. in 

 width extending from the front ranges 

 westward to the British Columbia 

 boundary upon the Continental divide. 

 The mountains trend sharply to the 

 northwest until the 120th meridian is 

 reached near the 54th parallel of lati- 

 tude. At this point the provincial 

 boundary turns northward and the 

 Rockies continue northwesterly into 

 British Columbia. The montane region 

 of Alberta broadens to the north with 

 a decrease in elevation. The higher 

 peaks reach an elevation of over 11,000 

 ft. The passes vary from 7000 ft. at 

 the South Kootenay pass in the south 

 to 3700 ft. at the Yellowhead pass in 

 the north. 



2. The Foothill region: The foothills 

 are extremely narrow or almost lacking 

 near the International boundary in 

 the south. As they follow the moun- 

 tains northward, however, they broaden 

 out forming an extensive area of low 

 rolling ridges with a general northwest 

 and southeast trend. 



S. The Alberta plateau: The Cretace- 

 ous plains extend eastward from the 

 foothills forming a high shelf-like pla- 

 teau which sinks gradually from an 

 elevation of 3500 ft. in the southwest 

 to 1500 ft. in the northeast. Along 

 the eastern boundary of the province 

 south of the North Saskatchewan River 

 the elevation averages 2000 ft. The 

 larger rivers have cut broad and deep 

 valleys in crossing the plateau eastward 

 from the mountains. The valley of the 

 Peace River in the north of the prov- 

 ince is in places upwards of 700 ft. 

 in depth and over two miles in width 

 from rim to rim. 



^. The northeastern -portion of the 

 province: This is occupied by a com- 

 paratively low flat plain having an 

 average elevation of 800 ft. above sea 

 level. The western portion of Lake 



Athabaska and the lower course of the 

 Peace River lie within this area. 



III. BIOTIC CONDITIONS 



The vegetation of Alberta may be 

 divided broadly into five climatic 

 formations. 



1. The Alpine belt extends along the 

 higher mountains above timber line. 

 Climatic conditions are severe with low 

 temperatures, a short growing season, 

 high and dry winter winds and low 

 atmospheric pressure. The climatic cli- 

 max is meadow-like and characterized 

 by heaths and saxifrages. 



2. The Montane belt occupies the 

 slopes of the mountains from timber 

 line to the eastern border of the foot- 

 hills. The precipitation varies between 

 20 and 30 in. and occurs mainly in the 

 spring and summer. The climatic cli- 

 max is a xeromesophytic coniferous 

 forest characterized by Engelmann 

 spruce {Picea Engelmannii), western 

 larch {Larix Lyallii), lodgepole pine 

 {Pinus murrayana), white spruce {Picea 

 canadensis) and Douglas fir {Pseudot- 

 suga mucronata). Limber pine {Pinus 

 Uexilis) and whitebark pine {Pinus 

 albicaulis) are found on the upper slopes 

 of the higher foothills and outer ranges 

 in the south. 



Engelmann spruce gives place to the 

 white spruce toward the north. West- 

 ern larch occurs well up to timber line 

 south of the Crow's Nest pass. Lodge- 

 pole pine in pure stands is very 

 extensive. 



3. The great plains in the south of the 

 province are occupied by a xerophytic 

 grassland climax which is an extension 

 northwards of the mixed Prairie Asso- 

 ciation of Montana. The precipitation 

 is in the neighborhood of 15 in., mainly 

 in the summer. The winters are dry 

 with little snow and marked by many 

 "Chinook winds." This condition ex- 

 tends north from the Montana boundary 

 to and beyond the Red Deer River. 

 Buffalo grass, grama grass and wire 

 grass are present, together with tumble 

 weed and sage brush. (The northern 



